US20100147569A1 - Component-embedded printed wiring board - Google Patents
Component-embedded printed wiring board Download PDFInfo
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- US20100147569A1 US20100147569A1 US12/709,573 US70957310A US2010147569A1 US 20100147569 A1 US20100147569 A1 US 20100147569A1 US 70957310 A US70957310 A US 70957310A US 2010147569 A1 US2010147569 A1 US 2010147569A1
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- Prior art keywords
- resin
- component
- preg
- circuit board
- temperature
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/18—Printed circuits structurally associated with non-printed electric components
- H05K1/182—Printed circuits structurally associated with non-printed electric components associated with components mounted in the printed circuit board, e.g. insert mounted components [IMC]
- H05K1/185—Components encapsulated in the insulating substrate of the printed circuit or incorporated in internal layers of a multilayer circuit
- H05K1/186—Components encapsulated in the insulating substrate of the printed circuit or incorporated in internal layers of a multilayer circuit manufactured by mounting on or connecting to patterned circuits before or during embedding
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/22—Secondary treatment of printed circuits
- H05K3/28—Applying non-metallic protective coatings
- H05K3/284—Applying non-metallic protective coatings for encapsulating mounted components
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/10—Bump connectors; Manufacturing methods related thereto
- H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
- H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
- H01L2224/161—Disposition
- H01L2224/16151—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
- H01L2224/16221—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
- H01L2224/16225—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/00011—Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/00014—Technical content checked by a classifier the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/19—Details of hybrid assemblies other than the semiconductor or other solid state devices to be connected
- H01L2924/191—Disposition
- H01L2924/19101—Disposition of discrete passive components
- H01L2924/19105—Disposition of discrete passive components in a side-by-side arrangement on a common die mounting substrate
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/30—Technical effects
- H01L2924/35—Mechanical effects
- H01L2924/351—Thermal stress
- H01L2924/3511—Warping
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/46—Manufacturing multilayer circuits
- H05K3/4644—Manufacturing multilayer circuits by building the multilayer layer by layer, i.e. build-up multilayer circuits
- H05K3/4652—Adding a circuit layer by laminating a metal foil or a preformed metal foil pattern
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/4913—Assembling to base an electrical component, e.g., capacitor, etc.
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/4913—Assembling to base an electrical component, e.g., capacitor, etc.
- Y10T29/49144—Assembling to base an electrical component, e.g., capacitor, etc. by metal fusion
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/4913—Assembling to base an electrical component, e.g., capacitor, etc.
- Y10T29/49146—Assembling to base an electrical component, e.g., capacitor, etc. with encapsulating, e.g., potting, etc.
Definitions
- the present invention relates to a component-embedded printed wiring board which includes electronic components built therein, and a method of manufacturing the same printed wiring board.
- FIG. 24 shows a structure of the conventional PWB which includes electronic components built therein.
- the conventional PWB comprises plate 1 made of metallic material, and substrates 2 a - 2 e formed of thermoplastic resin and layered over metallic plate 1 .
- Holes 4 are opened through substrates 2 c and 2 d for embedding electronic component 3 .
- Patterns 5 are provided on substrates 2 a - 2 e , and via-holes 7 opened through substrates 2 a - 2 e are filled with conductive paste 6 .
- Electrodes 8 placed at both sides of component 3 are conductive to paste 6 .
- Conductive paste 6 is made by mixing tin grains with silver grains. Between component 3 and holes 4 , clearance of 20 ⁇ m is provided surrounding component 3 for accurately positioning electrodes 8 with respect to via-holes 7 filled with paste 6 . Thus it can be said that the outside dimension of component 3 is approx. equal to 20 ⁇ m.
- the foregoing conventional PWB undergoes pressing and heating at 1-10 Mpa, 250-350° C. and in 10-20 minutes before completed. In other words, this pressing and heating process melts the tin to be unified with silver, and connects the tin to electrodes 8 of component 3 for fixing component 3 electrically and mechanically.
- the conventional component-embedded PWB is disclosed in, e.g. Japanese Patent Unexamined Publication No. 2003-86949.
- the conventional PWB has the following problem if components 3 are densely mounted.
- components 3 are densely mounted.
- electronic components 3 a - 3 e are mounted at a narrow pitch to substrate 2 c , and assume that an interval between the components adjacent to each other is 100 ⁇ m.
- FIG. 26A shows sectional views of substrates 2 c and 2 d
- FIG. 26B shows an enlarged view of the vicinity of components embedded.
- width W 1 of frame 10 a placed between electronic components 3 a and 3 b is found by equation 1.
- W 2 is, e.g. a distance between component 3 a and substrate 2 c surrounding component 3 a .
- W 1 becomes 60 ⁇ m, i.e. the width of frame 10 a is 60 ⁇ m.
- Thickness T 1 of substrate 2 c is 75 ⁇ m, so that width W 2 of frame 10 a becomes smaller than thickness T 1 of substrate 2 c , and it becomes physically difficult to manufacture this conventional PWB.
- holes 13 surrounding components 3 a - 3 e mounted at narrow pitches can be provided as shown in FIG. 27 (plan view) and FIG. 28 (sectional view).
- space 14 a between components 3 a and 3 b cannot be filled sufficiently with resin 15 , so that air 16 sometimes remains. If substrate 2 c in this status undergoes soldering in a reflow-oven, the reflow-temperature expands air 16 for applying heavy load between components 3 a and 3 b .
- the load has the possibility of damaging the connection of component 3 , to be more specific, the conduction of paste 6 is cut, or component 3 sealed with resin produces cracks into which water leaks for rusting electrodes 8 and causing defective insulation.
- a component-embedded printed wiring board (PWB) of the present invention comprises the following elements:
- FIG. 1 shows a sectional view of a component-embedded printed wiring board (PWB) in accordance with a first embodiment of the present invention.
- PWB printed wiring board
- FIG. 2 shows a flowchart illustrating steps of manufacturing the component-embedded PWB in accordance with the first embodiment.
- FIG. 3 shows a sectional view of the component-embedded PWB in the step of flux application in accordance with the first embodiment.
- FIG. 4 shows a sectional view of the component-embedded PWB in the step of cream-solder printing in accordance with the first embodiment.
- FIG. 5 shows a sectional view of the component-embedded PWB in the step of mounting electronic components in accordance with the first embodiment.
- FIG. 6 shows a sectional view of the component-embedded PWB in a reflow soldering step in accordance with the first embodiment.
- FIG. 7 shows a sectional view of the component-embedded PWB in the step of layering pre-pregs in accordance with the first embodiment.
- FIG. 8 shows an enlarged view of an essential part of the component-embedded PWB in the step of layering pre-pregs in accordance with the first embodiment.
- FIG. 9 shows a sectional view of the component-embedded PWB in a unifying step in accordance with the first embodiment.
- FIG. 10 shows a sectional view of the component-embedded PWB in an evacuating step in accordance with the first embodiment.
- FIG. 11 shows a sectional view of the component-embedded PWB in the step of heating and softening in accordance with the first embodiment.
- FIG. 12 shows a sectional view of the component-embedded PWB in a forcible flow-in step in accordance with the first embodiment.
- FIG. 13 shows a sectional view of the component-embedded PWB in the step of cutting in accordance with the first embodiment.
- FIG. 14 shows viscosity characteristics of epoxy resin in accordance with the first embodiment.
- FIG. 15 shows an enlarged view of a space formed around a semiconductor element in accordance with the first embodiment.
- FIG. 16A shows temperature characteristics in the unifying step in accordance with the first embodiment.
- FIG. 16B shows pressure characteristics in the unifying step in accordance with the first embodiment.
- FIG. 16C shows atmospheric-pressure characteristics in the unifying step in accordance with the first embodiment.
- FIG. 17 shows a flowchart illustrating the steps of manufacturing a component-embedded PWB in accordance with second and third embodiments.
- FIG. 18 shows a sectional view of a hanging device in accordance with the second embodiment.
- FIG. 19 shows a sectional view of a decompressing and layering device in accordance with the second embodiment.
- FIG. 20 show a sectional view of the component-embedded PWB used in a unifying step in accordance with the second embodiment.
- FIG. 21 shows a sectional view of a decompressing and layering device in accordance with the third embodiment.
- FIG. 22 shows another sectional view of the decompressing and layering device in accordance with the third embodiment.
- FIG. 23 shows a sectional view of the component-embedded PWB in the forcible flow-in step in accordance with the third embodiment.
- FIG. 24 shows an exploded sectional view of a conventional component-embedded PWB.
- FIG. 25 shows a plan sectional view taken from over the conventional component-embedded PWB.
- FIG. 26A shows a sectional view of an essential part of the conventional component-embedded PWB.
- FIG. 26B shows an enlarged top view of vicinity of components embedded in the conventional PWB.
- FIG. 27 shows a plan view of an essential part of the conventional component-embedded PWB.
- FIG. 28 shows a sectional view of an essential part of the conventional component-embedded PWB.
- FIG. 1 shows a sectional view of a component-embedded printed wiring board (PWB) in accordance with the first embodiment of the present invention.
- FIG. 2 shows a flowchart illustrating the steps of manufacturing the component-embedded PWB.
- FIG. 3-FIG . 12 detail respective manufacturing steps of the component-embedded PWB in accordance with the first embodiment.
- similar elements to those of the prior art have the same reference marks, and the descriptions thereof are simplified.
- Circuit board 101 shown in FIG. 1 is formed of thermosetting resin in a multi-layer structure.
- Board 101 has inner via-holes (not shown) which connect respective top faces to respective undersides of each layer.
- the respective top faces have copper foils thereon, and the foils form electric circuits respectively.
- Copper foil 145 is an example of conductive patterns which can employ printed wiring patterns formed of metallic powder paste.
- the top face of circuit board 101 has land patterns 104 a and 104 b thereon.
- Semiconductor element 105 mounted on the top face of board 101 is coupled to land pattern 104 a with solder bump 102 .
- Resistor 106 is coupled to land pattern 104 b with solder 107 .
- These components are used as examples of electronic components; other electronic components such as capacitors can be embedded.
- Solder 107 and bump 102 employ lead-free solder, namely, solder made of tin-, silver-, or copper-based metal, because these materials do not contain harmful substances and their environment load is low.
- solder 107 or bump 102 conductive adhesive having a thermosetting property can be used. This adhesive has a melting point higher than the solder, so that semiconductor element 105 or resistor 106 never comes off from circuit board 101 even in a high temperature environment such that soldering is carried out near these components.
- Component embedding layer 108 is sandwiched by circuit board 101 and copper foil 145 , and is filled with thermosetting resin. Layer 108 tightly seals semiconductor element 105 and resistor 106 at their peripheries.
- Layer 108 includes fluid-resin embedding section 108 a made of resin and covering both of semiconductor element 105 and resistor 106 , and substrate-included resin section 109 covering the periphery of fluid-resin embedding section 108 a .
- Substrate-included resin section 109 is formed by layering plural substrates 109 a , plural resins 110 b and 110 c alternately.
- plural substrates 109 a are used as an example of a resin flow-speed accelerator shaping like a board, and plural resins 110 b and 110 c are used as an example of bonding resin.
- Resin 110 c is placed between the lower most substrate 109 a and circuit board 101
- resin 110 d is placed between upper most substrate 109 a and copper foil 145 .
- Substrate 109 a of this embodiment has a thickness of approx. 80 ⁇ m
- resin 110 b has a thickness of approx. 10 ⁇ m
- resin 110 c and resin 110 d have a thickness of approx. 5 ⁇ m.
- Resin 110 is a collective term which includes resins 110 b - 110 d , and thermosetting resin such as epoxy resin is suitable for resin 110 .
- Fluid-resin embedding section 108 a is formed of thermosetting epoxy resin as is resin 110 . Since embedding section 108 a and resin 110 are made of the same resin, they have the same thermal expansion coefficient with respect to temperatures, so that a thermal change expands or contracts these two elements in the same amount. As a result, damage or breakage rarely occur in the boundary between embedding section 108 a and resin 110 .
- Substrate 109 a employs glass woven fabric, which prevents embedding section 108 a from being easily bent. Because if embedding section 108 a is formed of only epoxy resin, its flexural strength is weakened. As a result, smaller expansion and contraction due to thermal changes can be expected.
- glass woven fabric is used as substrate 109 a ; however, glass non-woven fabric or woven or non-woven fabric of other fibers such as aramid fiber can be used instead.
- Epoxy resin is used as fluid-resin embedding section 108 a and resin 110 ; however, other thermoplastic resin or thermosetting resin such as unsaturated polyester resin can be used instead with an advantage similar to the one obtained in this embodiment.
- Respective steps of a method of manufacturing the component-embedded PWB in accordance with the first embodiment are demonstrated hereinafter with reference to FIG. 3-FIG . 16 following the sequence of the steps shown in FIG. 2 .
- FIG. 2 shows a flowchart of manufacturing the component-embedded PWB in accordance with the first embodiment
- FIG. 3 shows a sectional view of the PWB in flux application step 111 .
- flux 112 is printed on land pattern 104 a , to which semiconductor element 105 (shown in FIG. 5 ) is to be mounted, through a metal screen (not shown).
- FIG. 4 shows a sectional view of the component-embedded PWB in step 113 of printing cream solder in accordance with the first embodiment.
- cream-solder printing step 113 follows flux application step 111 .
- cream solder 107 is printed on land pattern 104 b , to which resistor 106 (shown in FIG. 5 ) is to be mounted, with squeegee 132 and screen 131 .
- Cream solder 107 is used as an example of coupling and fixing member for connection.
- Screen 131 is a metal screen made of stainless steel, and recess 126 is formed on screen 131 at a place corresponding to flux 112 applied. Recess 126 prevents flux 112 from adhering to screen 131 during the printing of solder 107 .
- FIG. 5 shows a sectional view of the component-embedded PWB in step 114 of mounting electronic components in accordance with the first embodiment.
- step 114 of mounting the electronic components follows step 113 of printing the cream solder.
- semiconductor element 105 and resistor 106 are mounted onto circuit board 101 at given places by an automatic insertion machine.
- a plurality of solder bumps 102 are formed in advance on underside 105 a of semiconductor element 105 .
- FIG. 6 shows a sectional view of the component-embedded PWB in reflow soldering step 115 in accordance with the first embodiment.
- reflow soldering step 115 follows step 114 of mounting the electronic components.
- cream solder 107 is heated to a temperature higher than its melting point, so that cream solder 107 is melted, whereby resistor 106 is soldered to land pattern 104 b , and bumps 102 of semiconductor element 105 are soldered to land pattern 104 a .
- reflow soldering step 115 is carried out in nitrogen atmosphere, thereby preventing the surface of circuit board 101 from being oxidized. The contact between board 101 and pre-preg 141 a (shown in FIG. 7 ) is thus improved.
- in-process items can be washed in a step (not shown) of washing circuit board 101 , so that residue of flux 112 and solder balls are cleaned.
- O 2 asher process and silane coupling process are recommended, because these surface modifying processes improve the contact between board 101 and pre-preg 141 a.
- the reflow soldering is used because of its excellent quality.
- the reflow soldering allows fixing of the components soldered at given places due to its self-alignment effect, so that components can be accurately fixed to board 101 and the length of pattern-lines connected to these components becomes a definite value.
- the pattern lines are used as an inductor, the inductance can produce a definitive value, so that a given electrical performance can be expected. This is an important matter for a high-frequency circuit.
- FIG. 7 shows a sectional view of the component-embedded PWB in step 116 of layering pre-pregs in accordance with the first embodiment
- FIG. 8 shows an enlarged view of an essential part of the foregoing component-embedded PWB.
- hole-opening step 117 hole 142 is opened on pre-preg 141 for receiving semiconductor element 105 and resistor 106 therein.
- pre-pregs layering step 116 following reflow soldering step 115 pre-preg 141 with the hole is layered on circuit board 101 .
- Pre-preg 141 is a collective term which includes individual pre-pregs 141 a , 141 b , and 141 c .
- pre-preg 141 a includes resin 110 c , substrate 109 a and resin 110 b .
- Pre-preg 141 b includes resin 110 b , substrate 109 a and resin 110 b .
- Pre-preg 141 c includes resin 110 b , substrate 109 a and resin 110 d .
- Pre-preg 141 employs substrate 109 a made of non-woven fabric and impregnated with epoxy resin 110 c in advance to be unified. Substrate 109 a is used as an example of the resin flow-speed accelerator.
- pre-preg 141 is layered on circuit board 101 , so that a layered unit, where substrate 109 a , resins 110 b , 110 c and 110 d are layered one after another, is completed on circuit board 101 .
- Pre-preg 141 has a thickness of approx. 120 ⁇ m because substrate 109 a has a thickness of approx. 80 ⁇ m and is impregnated with resin 110 , thereby increasing the thickness to approx. 120 ⁇ m.
- Clearances 144 are reserved between the outer walls of resistor 106 and inner wall of hole 142 , so that pre-preg 141 with the hole can be layered on circuit board 101 with ease.
- clearances 144 can be reduced in size because semiconductor element 105 and resistor 106 are mounted precisely, which allows resin 110 to flow into spaces 156 , 157 with ease.
- clearances 144 take the maximum value of approx. 0.2 mm, so that even if resistor 106 is mounted deviating from a predetermined place, pre-preg 141 can be layered free from inconveniences such as collision.
- pre-preg 141 d On the upper most face of pre-preg 141 , pre-preg 141 d having no hole 142 is placed, and copper foil 145 is provided on the entire top face of pre-preg 141 d .
- resin 110 c of approx. 20 ⁇ m thickness, substrate 109 a of approx. 80 ⁇ m, and resin 110 b of 40 ⁇ m thickness are layered in this order from the bottom on circuit board 101 . Between the uppermost substrate 109 a and copper foil 145 , resin 110 d of approx. 20 ⁇ m thickness is layered.
- Pre-preg 141 d and copper foil 145 are used in this embodiment; however, a hardened circuit board can be used instead. Any hardened circuit-board such as a single-sided board, double-sided board, or multi-layer board can be used. Use of the hardened circuit board can reduce a warp of pre-preg 141 caused by thermal contraction in a cooling step described later.
- circuit board 101 layered in step 116 , pre-preg 141 and copper foil 145 undergo heating and pressing at a temperature slightly lower than the melting point of solder 107 , so that they are unified together.
- Step 118 is described hereinafter following the sequence of the steps shown in FIG. 2 .
- FIG. 9 shows a sectional view of a unifying device used in the unifying step in accordance with the first embodiment.
- the unifying device includes platens 151 and 152 , and circuit board 101 is mounted on platen 152 .
- Platens 151 , 152 , and expandable walls 153 on both sides form air-tight container 154 .
- a sucking device (not shown) is coupled to airtight container 154 .
- Heaters 160 are embedded in platens 151 , 152 for heating pre-preg 141 .
- Speed reducer 163 converts rotary motion into reciprocating motion, and also reduces the rotating speed.
- a control circuit (not shown) is coupled to driver 162 and heater 160 , and controls the timing that operates these two elements. Since resin 110 changes in viscosity in response to temperatures, the temperature of heater 160 is controlled in order to obtain a given viscosity of resin 110 .
- FIG. 10 shows a schematic sectional view of the unifying device employed in an evacuating step in accordance with the first embodiment.
- the first step in unifying step 118 is evacuating step 119 which follows pre-preg layering step 116 .
- the component-embedded PWB of which pre-preg 141 is layered on circuit board 101 is housed in air-tight container 154 .
- Platen 151 is fixed and platen 152 is movable.
- a sucking device sucks the air in airtight container 154 through vent hole 155 opened through platen 152 , so that airtight container 154 is decompressed to a substantially vacuum condition.
- the width of space 156 ranges from approx. 20 ⁇ m to approx. 350 ⁇ m
- the width of space 157 ranges from approx. 10 ⁇ m to approx. 40 ⁇ m.
- one semiconductor element 105 and two resistors 106 are used as examples of electronic components in this embodiment; however, more electronic components are actually mounted on circuit board 101 .
- a greater size of circuit board 101 is preferable, and therefore, more clearances 144 and spaces 156 , 157 exist practically.
- evacuating step 119 it is thus important to completely suck the air existing in these numerous clearances 144 and spaces 156 and 157 , because if the airs remain in pre-preg 141 , voids tend to occur.
- the following preparations are carried out:
- board-like pre-pregs 141 having no viscosity at a room temperature, i.e. solid pre-preg, are layered one after another in order to resist the occurrence of voids.
- hole 142 is evacuated before pre-preg 141 is softened.
- heaters 160 start working to heat platens 151 , 152 simultaneously with the start of evacuating step 119 , and driver 162 starts driving platens 152 , so that a given pressure is applied to the component-embedded PWB.
- This preparation shrinks expandable walls 153 , so that platen 152 is raised along arrow mark A as shown in FIG. 9 .
- circuit board 101 , layered pre-preg 141 and copper foil 145 are compressed completely between platens 151 and 152 by a predetermined pressure.
- Heaters 160 work at approx. 110° C., and a pressure of approx. 40 kg/cm 2 is used.
- FIG. 11 shows a sectional view of the unifying device used in a softening step in accordance with the first embodiment.
- evacuating step 119 is followed by heating and softening step 120 .
- Pre-preg 141 starts to be heated when platens 151 and 152 are brought into contact with circuit board 101 and copper foil 145 through evacuating step 119 .
- Resin 110 impregnated into pre-preg 141 is softened by the heat from heater 160 .
- Resin 110 is heated up to approx. 110° C., and its viscosity is lowered to approx. 2400 pa ⁇ s.
- Pre-preg 141 is compressed by platens 151 , 152 , which thus solidly contact the surface of copper foil 145 .
- the heat from heater 160 can thus be positively transferred to pre-preg 141 , so that a heating device excellent in energy efficiency and in saving energy is obtainable.
- FIG. 12 shows a sectional view of the unifying device in the forcible flow-in step in accordance with the first embodiment.
- heating and softening step 120 is followed by forcible flow-in step 122 , in which respective pre-pregs 141 are compressed into the thickness of approx. 90 ⁇ m.
- resins 110 b , 110 c , 110 d of pre-pregs 141 flow along substrate 109 a in the direction of arrow mark B (shown in FIG. 8 ), and flows into hole 142 .
- Eventually clearances 144 , spaces 156 and 157 are entirely filled with the resin flowing out from resins 110 b , 110 c , and 110 d , which are named sometimes collectively as resin 110 .
- the viscosity of resin 110 is preferably kept at a low level for the longest possible period. For this purpose, it is important to give resin 110 a viscosity which turns resin 110 fluid as quick as possible.
- heating and softening step 120 the temperature of pre-preg 141 is thus raised at a rate of 4.5° C./minute.
- pre-preg 141 is kept at 110° C. for 30 minutes and is compressed by the pressure of 40 kg/cm 2 .
- circuit board 101 and pre-preg 141 are heated unevenly depending on the locations of heaters 160 embedded in platens 151 , 152 . Temperature differences thus tend to occur on board 101 and pre-preg 141 due to this uneven heat.
- spaces 156 , 157 are formed away from platens 151 , 152 . Spaces 156 , 157 eventually have some points of which temperatures are lower than the temperature of resin 110 .
- the first embodiment thus keeps the temperature of 110° C. for approx. 30 minutes in forcible flow-in step 122 , so that the temperatures of spaces 156 , 157 and resin 110 become uniform, thereby preventing resin 110 from stopping its flow into the spaces caused by the temperature decrease.
- the movement of platen 152 is stopped by stopper 161 .
- heating and hardening step 123 hardens resin 110 .
- pre-preg 141 is heated to a temperature lower than a liquidus temperature of solder bump 102 and solder 107 , so that pre-preg 141 loses its fluidity and is completely hardened. In the meantime, at the liquidus temperature, solder becomes liquid completely by heating.
- step 123 it is important to heat pre-preg 141 so that it becomes hardened and loses its fluidity at a temperature lower than the liquidus temperature of solder bump 102 and solder 107 .
- Solder bump 102 and solder 107 employ lead-free solder that has a melting point of approx. 270° C., so that the temperature at which resin 110 loses its fluidity is preferably set not higher than 200° C. in step 123 .
- step 123 employs a pressure of 40 kg/cm 2 so that resin 110 can lose its fluidity at approx. 150° C. The viscosity of resin 110 at this time is approx. 24000 pa ⁇ s.
- heating and hardening step 123 makes resin 110 lose its fluidity completely, and then raises the temperature of resin 110 to 200° C. for hardening resin 110 . Since resin 110 loses its fluidity at approx. 150° C. in step 123 , connection between semiconductor 105 and circuit board 101 , or connection between resistors 106 and board 101 never comes off.
- pre-preg 141 After pre-preg 141 is hardened, the step moves on to cooling step 124 , where moderate cooling is slowly carried out.
- the component-embedded PWB sandwiched by platen 151 and platen 152 is slowly cooled by controlling the temperature of heaters 160 . This cooling is done until the temperature reaches not higher than the glass transition point (160° C. by TMA measuring method). Then water is poured into platens 151 , 152 for quickly cooling by the water.
- These preparations allow for a decrease in the difference in shrinkage amount between copper foil 145 and resin 110 caused by different coefficients of linear expansion of these two elements. As a result, warping of the component-embedded PWB can be reduced, and conductors on board 101 are prevented from peeling off from resin 110 at their interface.
- FIG. 13 shows a sectional view of a cutting device in cutting step 125 in accordance with the first embodiment.
- Cutting step 125 cuts resin 172 flowing out to the outside of circuit board 101 through forcible flow-in step 122 .
- the component-embedded PWB is cut by rotating dicing teeth 171 , which cuts not only surplus resin 172 but also both of circuit board 101 and resin 172 . Because circuit board 101 is cut inside the edge, the size of the component-embedded PWB becomes approx. a definite size regardless of expansion or contraction of circuit board 101 .
- heating and softening step 120 sharply heats the resin to be fluid, and heating and compressing step 118 a suppresses a temperature rise applied to pre-preg 141 as well as circuit board 101 and maintains the temperature.
- Step 118 a compresses pre-preg 141 at the temperature maintained so that circuit board 101 is unified with pre-preg 141 for completing component embedding layer 108 .
- step 118 a includes heating and softening step 120 and forcible flow-in step 122 .
- unifying step 118 resin 110 flows into spaces 156 and 157 . This movement is detailed hereinafter. First, the relation between a temperature, pressure and viscosity of resin 110 is described with reference to FIG. 14 .
- FIG. 14 shows viscosity characteristics of resin 110 measured by a viscosity tester.
- Lateral axis 201 represents temperatures, vertical axis 202 represents viscosity.
- curve 203 shows the viscosity on the assumption that the temperature rises at a given rate both in steps 120 and 122 .
- Curve 204 shows viscosity characteristics on the assumption that the temperature rises more moderately in forcible flow-in step 122 than in heating and softening step 120 .
- resin 110 is not viscous at room temperature, and it becomes softer and lowers its viscosity as the temperature rises.
- the viscosity reaches minimum viscosity 207 , and it increases as the temperature rises from temperature 206 , so that the hardening of resin 110 is quickened.
- minimum viscosity 207 of resin 110 becomes approx. 1150 pa ⁇ s.
- the fluidity of resin 110 is determined by a pressure applied to resin 110 and a viscosity, or a temperature of resin 110 .
- resin 110 attains a status of flow-start viscosity 217 at which resin 110 starts flowing at temperature 211 .
- resin 110 keeps a board-like status at a temperature ranging from room temperature to temperature 211 (first temperature range 213 ) and does not flow.
- flow-start viscosity is 24000 pa ⁇ s, and temperature 211 at this time is approx. 90° C.
- step 122 resin 110 is hardened in heating and hardening step 123 , in which platen 152 keeps applying the pressure of 40 kg/cm 2 .
- Epoxy resin 110 starts hardening gradually when its temperature falls within temperature range 215 (third temperature range) exceeding temperature 206 , and its viscosity reaches flow-start viscosity 212 , where it loses the fluidity, at temperature 216 .
- resin 110 loses its fluidity at 150° C., where its viscosity is 24000 pa ⁇ s.
- Resin 110 can maintain its viscosity, which allows resin 110 to flow into space 156 with ease at a specified pressure, for a long time. As a result, resin 110 is moved forcibly by pressure, so that hole 142 and space 156 are positively filled up with resin 110 .
- FIG. 15 shows an enlarged view of semiconductor element 105 in the forcible flow-in step in accordance with the first embodiment.
- FIG. 16A-16C show characteristics in unifying step 118 in accordance with the first embodiment.
- FIG. 10 shows resin 110 prior to compression, and resin 110 becomes fluid due to the compression by platen 152 , and then its tip, namely, resin 110 a , flows into space 156 .
- space 156 is so much smaller than clearance 144 that resin 110 a can be considered viscous fluid passing through a thin tube. Therefore, eddy 221 occurs near corner 105 b , thereby inviting pressure loss.
- solder bump 102 allows resin 110 to be considered viscous fluid passing through a thick tube after passing through the thin tube.
- resin 110 passing near solder bump 102 passes through thin tubes and thick tubes repeatedly, which invites a large amount of pressure loss, so that the flow speed of resin 110 slows down. It is important to increase the flow speed of resin 110 as much as possible so as not to stop the flow of resin 110 .
- the present invention provides fluid-resin embedding section 108 a with substrate 109 a made of glass woven fabric, and a cross sectional area through which resin 110 flows is reduced in the area where substrate 109 a exists.
- This preparation allows resin 110 to resist moving within substrate 109 a along arrow mark B show in FIG. 8 . Since pre-preg 141 has hole 142 , the compressing force in unifying step 118 is concentrated to substrate 109 a and resin 110 . On top of that, compressed resin 110 flows through a space having a small sectional area and sandwiched between substrates 109 a . This mechanism allows resin 110 to flow at a higher speed with respect to a compressed amount (or a compressing pressure) by platen 152 .
- FIG. 16A shows relations between time, resin temperature and resin viscosity
- FIG. 16B shows relation between time and pressure
- FIG. 16C shows relation between time and degrees of vacuum.
- lateral axis 231 represents the time (minutes)
- first vertical axis 232 represents the temperature (° C.)
- second vertical axis 233 represents the viscosity (pa ⁇ s) of FIG. 16A
- Vertical axis 234 of FIG. 16B represents the pressure (kg/cm 2 )
- vertical axis 235 of FIG. 16C represents the degree of vacuum (torr).
- curve 238 shows the temperature of pre-preg 141
- curve 239 shows the viscosity of resin 110
- the temperature is raised to temperature 240 in order to make resin 110 fluid.
- Temperature 240 is approx. 90° C. in this embodiment, and resin 110 is heated at a rate of approx. 4.5° C./minute so that the temperature reaches temperature 240 in approx. 15 minutes, and the viscosity lowers to viscosity 248 .
- the viscosity of resin 110 used in this embodiment becomes approx. 24000 pa ⁇ s at 90° C., and resin 110 starts flowing at this viscosity with respect to the pressure of 40 kg/cm 2 applied by platen 152 .
- step 122 Forcible flow-in step 122 is carried out after the viscosity of resin 110 is lowered to a fluid level in step 120 .
- step 122 the temperature is further raised to temperature 241 while pressure 249 continues to be supplied, and temperature 241 is maintained for approx. 30 minutes to allow resin 110 to forcibly flow into space 156 .
- step 120 it is preferable to heat resin 110 as quick as possible so that the viscosity lowers to not higher than viscosity 248 , and in step 122 , it is preferable to maintain the temperature of resin 110 at temperature 241 .
- a pressure applied to resin 110 at the start of being fluid is preferably greater than that applied upon losing its fluidity, because a greater pressure produces a greater flow-speed of resin 110 flowing into clearance 144 and space 156 , which are thus positively filled with resin 110 .
- Pre-preg 141 layered in layering step 116 is provided with clearance 144 around or above semiconductor element 105 and resistor 106 .
- the pressure applied from platen 152 in unifying step 118 a is concentrated to pre-preg 141 at its face 146 (shown in FIG. 8 ) except hole 142 , so that resin 110 receives a pressure greater than the pressure supplied from platen 152 .
- Hole 142 is not prepared for semiconductor element 105 and resistor 106 individually, but it is prepared for surrounding all these elements, so that hole 142 occupies almost a half area of board 101 .
- pressure as much as twice of the pressure (40 kg/cm 2 ) supplied from platen 152 can be applied to resin 110 , namely 80 kg/cm 2 is applied to resin 110 .
- This mechanism allows resin 110 to become fluid at a greater viscosity (or a lower temperature) than flow-start viscosity 212 , so that a fluidable period can be prolonged.
- resin 110 can be positively charged into clearance 144 and space 156 with more ease.
- Heating and hardening step 123 follows forcible flow-in step 122 where space 156 is filled up with resin 110 .
- step 123 the temperature of resin 110 is raised over temperature 245 at which resin 110 loses it fluidity under pressure 249 , so that resin 110 becomes non-fluid, i.e. does not move in the least.
- the viscosity at which resin 110 loses it fluidity under pressure 249 is almost the same as viscosity 248 at which the fluidity starts working, so that the viscosity is approx. 24000 pa ⁇ s.
- heating and hardening step 123 the temperature of resin 110 is raised to 200° C., and resin 110 is kept at this temperature for approx. 60 minutes to be hardened completely.
- the foregoing method does not need a step of putting intermediate members or the intermediate members per se, so that an inexpensive component-embedded PWB is obtainable. Further, in forcible flow-in step 122 , small spaces 156 , 157 can be positively filled up with resin 110 , so that few voids occur and a reliable component-embedded PWB is obtainable.
- platen 152 can apply a pressure of as much as 40 kg/cm 2 for compressing because of the following structure:
- pre-preg 141 is layered such that hole 142 exists over semiconductor element 105 and resistor 106 , so that platen 152 cannot apply its pressure directly to semiconductor element 105 or resistor 106 . Since the foregoing great pressure can be supplied, resin 110 is positively charged into clearance 144 and space 156 .
- pre-preg 141 is made of thermosetting resin, once it is heated and hardened, it never returns to plastic status even if it is heated again. Thus once semiconductor element 105 is sealed by resin 110 , it keeps being fixed.
- the glass woven fabric is impregnated with epoxy resin, so that when resin 110 becomes fluid in heating and softening step 120 and forcible flow-in step 122 , pre-preg 141 can keep its shape as a substrate, so that a component-embedded PWB having dimensional accuracy is obtainable.
- Temperature 246 (shown in FIG. 16A ) in heating and hardening step 123 is kept lower than the melting point of solder 107 .
- solder 107 employs high-temperature solder of which melting point is higher than the temperature maintained in step 123 . This preparation allows solder 107 not to be melted by the heat supplied from step 123 , so that a more reliable component-embedded PWB is obtainable.
- the temperature maintained in the forcible flow-in step is low enough (e.g. 150° C.) not to melt the solder which connects and fixes semiconductor element 105 and resistors 106 , and yet circuit board 101 and pre-preg 141 are unified together at the temperature maintained. This unification thus does not break the connection or the fixation. As a result, semiconductor element 105 and resistor 106 can be kept in strong connection and fixation.
- Semiconductor element 105 and resistor 106 are mounted on circuit board 101 , so that an inspection can be carried out for this circuit board 101 with the components mounted. As a result, a non-defective rate after completing the component-embedded PWB can be improved.
- a plurality of pre-pregs 141 are layered one after another; however, substrates 109 a can be layered independently and resins 110 can be layered also independently. In such a case, the flow-speed of resin 110 can be changed appropriately in response to a thickness of the component-embedded PWB.
- overshooting temperature range 247 which temporarily exceeds temperature 241 is provided.
- This preparation allows the temperature in heating and softening step 120 to rise more quickly, so that the viscosity of resin 110 lowers quickly.
- the highest temperature in overshooting temperature range 247 is 115° C., and this highest temperature is preferably set lower than temperature 244 (125° C. in this embodiment) at which resin 110 starts being hardened by the pressure supplied.
- the amount of resin 110 to be layered on circuit board 101 should be a greater amount than a fill-up amount of the resin charged into clearance 144 , and spaces 156 , 157 . Because even if pre-preg 141 has dispersion in thickness, substrate 109 a has dispersion, or the condition such as pressure or temperature has dispersion, clearance 144 and spaces 156 , 157 should be positively filled up with resin 110 . However, if too much resin is supplied, a large amount of resin 110 sticks out wastefully to the outside of board 101 . To overcome this possible problem, this embodiment uses substrate 109 a , which accelerates the flow-speed of resin 110 , so that clearance 144 and spaces 156 , 157 can be filled up with resin 110 leaving as little as possible left over.
- the surplus supply of resin 110 sometimes increases the resin pressure in clearance 144 and spaces 156 , 157 in unifying step 118 a , and the resin pressure remains as stress, which generates warp. If the stress becomes excessive, it can damage the components.
- the compression to be done in unifying step 118 a should be carried out such that resin layers 110 can be formed between substrate 109 a and board 101 , between substrates 109 a themselves, and between substrate 109 a and copper foil 145 . Such compression allows resin 110 supplied excessively to flow toward the outside of board 101 with ease.
- substrate-included resin section 109 is formed by layering plural substrates 109 a and plural resins 110 b and 110 c alternately.
- substrate 109 a is used as an example of the resin flow-speed accelerator, and both of resins 110 b and 110 c are used as examples of bonding resin.
- a fluid period of resin 110 is prolonged or a pressure applied to resin 110 is changed in response to the heating condition.
- resin 110 flows into hole 142 with ease, so that the spaces between semiconductor element 105 and resistor 106 can be filled up thoroughly with the resin without providing, for example, a substrate which is conventionally disposed between semiconductor element 105 and resistor 106 .
- FIG. 17 shows a flowchart illustrating the steps of manufacturing a component-embedded printed wiring board (PWB) in accordance with this second embodiment.
- PWB printed wiring board
- FIGS. 17-20 similar elements to those shown in FIGS. 1-12 have the same reference marks, and the descriptions thereof are simplified here.
- the first embodiment previously discussed six sheets of pre-pregs 141 are layered on circuit board 101 ; however, in this embodiment, only one sheet of pre-preg having a thickness of approx. 1 mm is layered on circuit board 101 .
- the respective steps are detailed hereinafter following the sequence of the steps shown in FIG. 17 .
- semiconductor element 105 and resistor 106 are mounted on circuit board 101 , and they undergo the soldering in reflow soldering step 115 .
- hanging step 300 is prepared for hanging pre-preg 302 over circuit board 101 .
- Hanging step 300 is followed by decompressing and layering step 301 .
- Pre-preg 302 is used as an example of a sheet.
- FIG. 18 shows a sectional view of a hanging device in accordance with the second embodiment.
- FIG. 19 shows a sectional view of a decompressing and layering device in accordance with the second embodiment.
- airtight container 311 includes platen 152 , guide 312 surrounding lateral faces of circuit board 101 , slope 313 disposed to the upper end of guide 312 , and opening 314 existing over guide 312 .
- Airtight container 311 is used as an example of an airtight device, and platen 152 is used as an example of a compressing device.
- Circuit board 101 is inserted into guide 312 of airtight container 311 .
- the clearance between guide 312 and board 101 is approx. 0.5 mm on each side, and guide 312 determines the position of board 101 .
- Pre-preg 302 is placed such that it covers opening 314 .
- Width 315 of pre-preg 302 should be greater than width 316 of guide 312 and yet smaller than opening size 313 a of slope 313 .
- Such dimensions allow pre-preg 302 to be hung by slope 313 in hanging step 300 .
- Copper foil 145 is layered on pre-preg 302 .
- slope 313 hangs pre-preg 302 so that pre-preg 302 cannot touch semiconductor element 105 or resistor 106 because this hanging-up provides a clearance between the underside of pre-preg 302 and the top face of semiconductor element 105 or resistor 106 .
- Slope 313 thus works as a hanging device.
- Pre-preg 302 used in this second embodiment employs epoxy resin 317 in a liquid state, i.e. having a viscosity, at a room temperature, because quicker lowering in viscosity needs less heating, so that a component-embedded PWB can be produced with less energy.
- Tip 302 a of pre-preg 302 thus closely contacts slope 313 , so that an airtight space is formed by platen 152 , guide 312 , slope 313 and pre-preg 302 .
- pre-preg 302 per se works as a lid of airtight container 311 .
- Epoxy resin 317 can be replaced with thermosetting resin such as unsaturated polyester resin.
- a sucking device (not shown) sucks the air from the airtight space covered with pre-preg 302 working as a lid through vent hole 318 provided to guide 312 . Decompressing the airtight space makes the inside of container 311 negatively pressurized, so that pre-preg 302 lowers along slope 313 and guide 312 .
- vent hole 318 is provided near the lower end of guide 312 , and it is preferable to provide hole 318 at a place lower than pre-preg 302 is supposed to sink through decompression. This structure prevents pre-preg 302 from covering vent hole 318 when the air is sucked through vent hole 318 , so that container 311 can be evacuated positively.
- FIG. 19 shows a sectional view of a decompressing and layering device in accordance with the second embodiment.
- pre-preg 302 stops lowering when it touches top face 105 c of the semiconductor element or top face 106 a of the resistor, so that pre-preg 302 is layered over circuit board 101 .
- Pre-preg 302 is thus held in a negatively pressurized status due to the evacuating.
- FIG. 20 show a sectional view of a unifying device to be used in unifying step 303 which follows the compressing and layering step in accordance with the second embodiment.
- upper platen 321 heats, compresses, and cools pre-preg 302 , thereby charging epoxy resin 317 into spaces 156 , 157 , and unifying circuit board 101 and pre-preg 302 together.
- the first step of unifying step 303 is heating and softening step 304 which follows decompressing and layering step 301 .
- step 304 heaters 160 provided to platen 152 and upper platen 321 apply heat to pre-preg 302 so that pre-preg 302 is softened to be fluid. Since pre-preg 302 employs fluid material at a room temperature, step 304 needs less heat, i.e. energy can be saved.
- epoxy resin 317 flows in as it does in the first embodiment. In this second embodiment, it is also important to move platen 321 in order to prevent epoxy resin 317 flowing into spaces 156 , 157 from being heated over the temperature, at which the resin starts hardening, by frictional heat or pressure loss due to the flow-in.
- epoxy resin 317 is forcibly charged into spaces 156 , 157 at approx. 100° C., so that there is no need to charge an intermediate member into spaces 156 , 157 in another step.
- Epoxy resin 317 starts hardening at a temperature ranging from 110° C. to 150° C. This embodiment uses epoxy resin 317 that starts a thermosetting reaction when the resin is held for approx. 10 minutes in the foregoing temperature range.
- pre-preg 302 does not have a hole, so that spaces 331 formed around semiconductor element 105 and resistor 106 are greater than clearances 143 , 144 formed in the first embodiment.
- the temperature in forcible flow-in step 305 is set at 100° C., thereby charging epoxy resin 317 positively into spaces 331 , 156 , 157 .
- Step 305 is followed by heating and hardening step 306 .
- epoxy resin 317 is heated to 150° C. to be completely hardened, and then hardened resin 317 is cooled gradually in cooling step 124 and is cut in cutting step 125 following step 124 .
- step 305 it is also important to set a temperature rising rate in step 305 smaller than that in step 304 .
- This preparation allows lowering the viscosity of pre-preg 141 quickly and minimizing the viscosity, so that the resin is positively charged into the spaces in step 305 .
- Compressing and layering step 301 is carried out ahead of unifying step 303 , so that no bubbles containing air remain between pre-preg 302 and semiconductor element 105 or resistor 106 , and more solid contact can be expected between pre-preg 302 and top face 105 c of semiconductor element 105 or top face 106 a of resistor 106 . As a result, a reliable component-embedded PWB is obtainable.
- Pre-preg 302 does not need a hole corresponding to semiconductor element 105 and resistor 106 as it is needed in the first embodiment, so that hole-opening step 117 in the first embodiment is not needed here. As a result, an inexpensive component-embedded PWB is obtainable.
- pre-preg 302 can be just placed over slope 313 , so that layering work can be simplified, which also reduces the cost of the component-embedded PWB.
- vent holes 318 are provided to guide 312 , so that the clearance between board 101 and guide 312 can be narrowed.
- Guide 312 thus accurately determines the position of board 101 , and also prevents pre-preg 302 from flowing out to the outside.
- This structure allows epoxy resin 317 to flow into spaces 331 , 156 , 157 , thereby positively charging these spaces with resin 317 so as to be free of voids.
- FIGS. 21 and 22 show sectional views of the decompressing and layering device used in the decompressing and layering step in accordance with the third embodiment.
- FIG. 23 shows a sectional view of the component-embedded PWB in the forcible flow-in step of the third embodiment.
- elements similar to those used in FIG. 1-FIG . 20 sometimes have the same reference marks, and in such cases the descriptions thereof are simplified.
- platens 151 , 152 and expandable wall 153 form airtight container 154 .
- Circuit board 101 on which semiconductor element 105 and resistor 106 have been reflow-soldered, is mounted to platen 152 at a given place.
- Airtight container 154 is used as an example of an airtight device.
- Platen 151 has holding gadget 401 mounted rotatably on shaft 402 , and holding gadget 401 is urged inward by springs (not shown), thereby pinching pre-preg 302 at both sides. Holding gadget 401 and platen 151 hold pre-preg 302 such that pre-preg 302 confronts circuit board 101 .
- Platen 151 and holding gadget 401 form a hanging device, thereby preventing pre-preg 302 from touching semiconductor element 105 or resistor 106 .
- This structure allows forming clearance 403 between underside of pre-preg 302 and top face of semiconductor element 105 or resistor 106 .
- a sucking device (not shown) sucks the air from the airtight container through vent holes 155 , so that the container is decompressed and evacuated, which makes container 154 negatively pressurized, thereby raising platen 152 .
- FIG. 22 shows a sectional view of the decompressing and layering device used in the decompressing and layering step in accordance with the third embodiment.
- pre-preg 302 is halted keeping in touch with the top faces of semiconductor element 105 and resistor 106 , so that pre-preg 302 is layered over the circuit board 101 .
- Pre-preg 302 is thus held in negative pressurized status due to the evacuating.
- FIG. 23 shows a sectional view of a unifying device used in unifying step 303 .
- upper platen 151 heats, compresses, and cools pre-preg 302 , thereby charging epoxy resin 317 into spaces 156 , 157 , and unifying circuit board 101 and pre-preg 302 together.
- tip 401 a of holding gadget 401 stops when it touches platen 152 .
- holding gadget 401 also works as stopper 161 described in the first embodiment.
- holding gadget 401 is placed such that it covers the entire periphery of pre-preg 302 , so that holding gadget 401 prevents fluid epoxy resin 317 from flowing out to the outside in unifying step 303 .
- Epoxy resin 317 thus flows into spaces 331 , 156 , 157 , thereby inviting no voids. As a result, these spaces are positively filled up with resin 317 .
- the pre-preg can be downsized proportionately, which can reduce an amount of pre-preg 302 , and an inexpensive component-embedded PWB is obtainable.
- the thermosetting resin cannot be reused once it is hardened, so that the reduction of the amount of pre-preg 302 can contribute to environmental protection.
- holding gadget 401 moves outward (along the arrow mark shown in FIG. 22 ) for releasing pre-preg 302 , so that platen 151 can move upward and circuit board 101 can be taken out.
- Compressing and layering step 301 is carried out ahead of unifying step 303 , so that no bubbles containing air remain between pre-preg 302 and semiconductor element 105 or resistor 106 , and more solid contact can be expected between pre-preg 302 and top face 105 c of semiconductor element 105 or top face 106 a of resistor 106 . As a result, a reliable component-embedded PWB is obtainable.
- Pre-preg 302 does not need a hole corresponding to semiconductor element 105 and resistor 106 as it is needed in the first embodiment, so that hole-opening step 117 in the first embodiment is not needed here. As a result, an inexpensive component-embedded PWB is obtainable.
- holes in response to heights of respective components are not needed, so that one sheet of pre-preg 302 can work sufficiently.
- one sheet of pre-preg 302 is layered, which reduces the cost of the component-embedded PWB.
- pre-preg 302 can be just pinched by holding gadget 401 , so that layering work can be simplified, which also reduces the cost of the component-embedded PWB.
- pre-preg 302 is hung; however, circuit board 101 can be hung instead. In such a case, a similar advantage to what is discussed above is also obtainable.
- the component-embedded PWB of the present invention includes the following elements:
- the component-embedded PWB and the manufacturing method of the same PWB of the present invention can advantageously provide reliable connections in the component-embedded PWB.
- Use of the same PWB as the boards, on which components are reflow-soldered, is useful.
Abstract
A component-embedded printed wiring board (PWB) is disclosed. This PWB includes (a) a fluid-resin embedding section formed at a location corresponding to electronic components such that the embedding section covers the electronic components, (b) a resin flow-speed accelerator placed in parallel with a top face of a circuit board and surrounding the embedding section, and (c) bonding resin placed at least between the accelerator and the circuit board. The fluid resin embedding section is filled up with the same resin as the bonding resin. This structure allows the accelerator to compress the resin with pressure applied to the PWB, so that the resin tends to flow along the circuit board. As a result, the fluid-resin embedding section is thoroughly filled up with the resin without leaving any air, and the reliable PWB is thus obtainable.
Description
- This application is a Divisional of U.S. application Ser. No. 11/434,763, filed May 17, 2006.
- The present invention relates to a component-embedded printed wiring board which includes electronic components built therein, and a method of manufacturing the same printed wiring board.
- A conventional component-embedded printed wiring board (PWB) is described hereinafter.
FIG. 24 shows a structure of the conventional PWB which includes electronic components built therein. As shown inFIG. 24 , the conventional PWB comprises plate 1 made of metallic material, andsubstrates 2 a-2 e formed of thermoplastic resin and layered over metallic plate 1. -
Holes 4 are opened throughsubstrates electronic component 3.Patterns 5 are provided onsubstrates 2 a-2 e, and via-holes 7 opened throughsubstrates 2 a-2 e are filled withconductive paste 6.Electrodes 8 placed at both sides ofcomponent 3 are conductive to paste 6. -
Conductive paste 6 is made by mixing tin grains with silver grains. Betweencomponent 3 andholes 4, clearance of 20 μm is provided surroundingcomponent 3 for accurately positioningelectrodes 8 with respect to via-holes 7 filled withpaste 6. Thus it can be said that the outside dimension ofcomponent 3 is approx. equal to 20 μm. - The foregoing conventional PWB undergoes pressing and heating at 1-10 Mpa, 250-350° C. and in 10-20 minutes before completed. In other words, this pressing and heating process melts the tin to be unified with silver, and connects the tin to
electrodes 8 ofcomponent 3 forfixing component 3 electrically and mechanically. The conventional component-embedded PWB is disclosed in, e.g. Japanese Patent Unexamined Publication No. 2003-86949. - The conventional PWB, however, has the following problem if
components 3 are densely mounted. For instance, as shown inFIG. 25 ,electronic components 3 a-3 e are mounted at a narrow pitch tosubstrate 2 c, and assume that an interval between the components adjacent to each other is 100 μm.FIG. 26A shows sectional views ofsubstrates FIG. 26B shows an enlarged view of the vicinity of components embedded. As shown inFIGS. 26A and 26B , width W1 offrame 10 a placed betweenelectronic components -
W1=W0−W2×2 (1) - where W2 is, e.g. a distance between
component 3 a andsubstrate 2c surrounding component 3 a. In this case, since W0=100 μm and W2=20 μm, W1 becomes 60 μm, i.e. the width offrame 10 a is 60 μm. - Thickness T1 of
substrate 2 c is 75 μm, so that width W2 offrame 10 a becomes smaller than thickness T1 ofsubstrate 2 c, and it becomes physically difficult to manufacture this conventional PWB. - To overcome this problem,
holes 13 surroundingcomponents 3 a-3 e mounted at narrow pitches can be provided as shown inFIG. 27 (plan view) andFIG. 28 (sectional view). In this case, however,space 14 a betweencomponents resin 15, so thatair 16 sometimes remains. Ifsubstrate 2 c in this status undergoes soldering in a reflow-oven, the reflow-temperature expandsair 16 for applying heavy load betweencomponents component 3, to be more specific, the conduction ofpaste 6 is cut, orcomponent 3 sealed with resin produces cracks into which water leaks for rustingelectrodes 8 and causing defective insulation. - A component-embedded printed wiring board (PWB) of the present invention comprises the following elements:
-
- a fluid resin embedding section formed at a place corresponding to electronic components embedded such that it covers the electronic components;
- a resin flow-speed accelerator disposed in parallel with a top face of a circuit board such that it surrounds the fluid resin embedding section; and
- bonding resin disposed between the resin flow-speed accelerator and the circuit board.
The fluid resin embedding section is filled up with the same resin as the bonding resin. This structure enables the provision of a component-embedded PWB of high connection reliability.
-
FIG. 1 shows a sectional view of a component-embedded printed wiring board (PWB) in accordance with a first embodiment of the present invention. -
FIG. 2 shows a flowchart illustrating steps of manufacturing the component-embedded PWB in accordance with the first embodiment. -
FIG. 3 shows a sectional view of the component-embedded PWB in the step of flux application in accordance with the first embodiment. -
FIG. 4 shows a sectional view of the component-embedded PWB in the step of cream-solder printing in accordance with the first embodiment. -
FIG. 5 shows a sectional view of the component-embedded PWB in the step of mounting electronic components in accordance with the first embodiment. -
FIG. 6 shows a sectional view of the component-embedded PWB in a reflow soldering step in accordance with the first embodiment. -
FIG. 7 shows a sectional view of the component-embedded PWB in the step of layering pre-pregs in accordance with the first embodiment. -
FIG. 8 shows an enlarged view of an essential part of the component-embedded PWB in the step of layering pre-pregs in accordance with the first embodiment. -
FIG. 9 shows a sectional view of the component-embedded PWB in a unifying step in accordance with the first embodiment. -
FIG. 10 shows a sectional view of the component-embedded PWB in an evacuating step in accordance with the first embodiment. -
FIG. 11 shows a sectional view of the component-embedded PWB in the step of heating and softening in accordance with the first embodiment. -
FIG. 12 shows a sectional view of the component-embedded PWB in a forcible flow-in step in accordance with the first embodiment. -
FIG. 13 shows a sectional view of the component-embedded PWB in the step of cutting in accordance with the first embodiment. -
FIG. 14 shows viscosity characteristics of epoxy resin in accordance with the first embodiment. -
FIG. 15 shows an enlarged view of a space formed around a semiconductor element in accordance with the first embodiment. -
FIG. 16A shows temperature characteristics in the unifying step in accordance with the first embodiment. -
FIG. 16B shows pressure characteristics in the unifying step in accordance with the first embodiment. -
FIG. 16C shows atmospheric-pressure characteristics in the unifying step in accordance with the first embodiment. -
FIG. 17 shows a flowchart illustrating the steps of manufacturing a component-embedded PWB in accordance with second and third embodiments. -
FIG. 18 shows a sectional view of a hanging device in accordance with the second embodiment. -
FIG. 19 shows a sectional view of a decompressing and layering device in accordance with the second embodiment. -
FIG. 20 show a sectional view of the component-embedded PWB used in a unifying step in accordance with the second embodiment. -
FIG. 21 shows a sectional view of a decompressing and layering device in accordance with the third embodiment. -
FIG. 22 shows another sectional view of the decompressing and layering device in accordance with the third embodiment. -
FIG. 23 shows a sectional view of the component-embedded PWB in the forcible flow-in step in accordance with the third embodiment. -
FIG. 24 shows an exploded sectional view of a conventional component-embedded PWB. -
FIG. 25 shows a plan sectional view taken from over the conventional component-embedded PWB. -
FIG. 26A shows a sectional view of an essential part of the conventional component-embedded PWB. -
FIG. 26B shows an enlarged top view of vicinity of components embedded in the conventional PWB. -
FIG. 27 shows a plan view of an essential part of the conventional component-embedded PWB. -
FIG. 28 shows a sectional view of an essential part of the conventional component-embedded PWB. - The first exemplary embodiment of the present invention is demonstrated hereinafter with reference to
FIG. 1-FIG . 12.FIG. 1 shows a sectional view of a component-embedded printed wiring board (PWB) in accordance with the first embodiment of the present invention.FIG. 2 shows a flowchart illustrating the steps of manufacturing the component-embedded PWB.FIG. 3-FIG . 12 detail respective manufacturing steps of the component-embedded PWB in accordance with the first embodiment. In these drawings, similar elements to those of the prior art have the same reference marks, and the descriptions thereof are simplified. - The construction of the component-embedded PWB in accordance with the first embodiment is described with reference to
FIG. 1 .Circuit board 101 shown inFIG. 1 is formed of thermosetting resin in a multi-layer structure.Board 101 has inner via-holes (not shown) which connect respective top faces to respective undersides of each layer. The respective top faces have copper foils thereon, and the foils form electric circuits respectively.Copper foil 145 is an example of conductive patterns which can employ printed wiring patterns formed of metallic powder paste. - The top face of
circuit board 101 hasland patterns Semiconductor element 105 mounted on the top face ofboard 101 is coupled toland pattern 104 a withsolder bump 102.Resistor 106 is coupled toland pattern 104 b withsolder 107. These components are used as examples of electronic components; other electronic components such as capacitors can be embedded. -
Solder 107 and bump 102 employ lead-free solder, namely, solder made of tin-, silver-, or copper-based metal, because these materials do not contain harmful substances and their environment load is low. Instead ofsolder 107 or bump 102, conductive adhesive having a thermosetting property can be used. This adhesive has a melting point higher than the solder, so thatsemiconductor element 105 orresistor 106 never comes off fromcircuit board 101 even in a high temperature environment such that soldering is carried out near these components. -
Component embedding layer 108 is sandwiched bycircuit board 101 andcopper foil 145, and is filled with thermosetting resin.Layer 108 tightly sealssemiconductor element 105 andresistor 106 at their peripheries. -
Layer 108 includes fluid-resin embedding section 108 a made of resin and covering both ofsemiconductor element 105 andresistor 106, and substrate-includedresin section 109 covering the periphery of fluid-resin embedding section 108 a. Substrate-includedresin section 109 is formed by layeringplural substrates 109 a,plural resins plural substrates 109 a are used as an example of a resin flow-speed accelerator shaping like a board, andplural resins -
Resin 110 c is placed between the lowermost substrate 109 a andcircuit board 101, andresin 110 d is placed between uppermost substrate 109 a andcopper foil 145.Substrate 109 a of this embodiment has a thickness of approx. 80 μm,resin 110 b has a thickness of approx. 10 μm,resin 110 c andresin 110 d have a thickness of approx. 5 μm. - The foregoing structure, i.e.
layering substrates 109 a one after another, allowssubstrate 109 a to accelerate a flow speed ofresins 110 layered oncircuit board 101 along the surface ofboard 101 in a unifying step described later, so that the fluid-resin embedding section has every nook and cranny filled with the resin. As a result, no air remains. This structure, therefore, allows the load produced by thermal expansion of the air not to damage the connections, and improves the connection reliability.Resin 110 is a collective term which includesresins 110 b-110 d, and thermosetting resin such as epoxy resin is suitable forresin 110. - Fluid-
resin embedding section 108 a is formed of thermosetting epoxy resin as isresin 110. Since embeddingsection 108 a andresin 110 are made of the same resin, they have the same thermal expansion coefficient with respect to temperatures, so that a thermal change expands or contracts these two elements in the same amount. As a result, damage or breakage rarely occur in the boundary between embeddingsection 108 a andresin 110. - Since
resin 110 c is disposed betweensubstrate 109 a andcircuit board 101, peel-off rarely occurs betweencomponent embedding layer 108 andcircuit board 101. On top of that, sinceresin 110 d is disposed betweensubstrate 109 a andcopper foil 145, peel-off rarely occurs betweencomponent embedding layer 108 andcopper foil 145. -
Substrate 109 a employs glass woven fabric, which prevents embeddingsection 108 a from being easily bent. Because if embeddingsection 108 a is formed of only epoxy resin, its flexural strength is weakened. As a result, smaller expansion and contraction due to thermal changes can be expected. - In this embodiment, glass woven fabric is used as
substrate 109 a; however, glass non-woven fabric or woven or non-woven fabric of other fibers such as aramid fiber can be used instead. Epoxy resin is used as fluid-resin embedding section 108 a andresin 110; however, other thermoplastic resin or thermosetting resin such as unsaturated polyester resin can be used instead with an advantage similar to the one obtained in this embodiment. - Respective steps of a method of manufacturing the component-embedded PWB in accordance with the first embodiment are demonstrated hereinafter with reference to
FIG. 3-FIG . 16 following the sequence of the steps shown inFIG. 2 . -
FIG. 2 shows a flowchart of manufacturing the component-embedded PWB in accordance with the first embodiment, andFIG. 3 shows a sectional view of the PWB influx application step 111. Instep 111,flux 112 is printed onland pattern 104 a, to which semiconductor element 105 (shown inFIG. 5 ) is to be mounted, through a metal screen (not shown). -
FIG. 4 shows a sectional view of the component-embedded PWB instep 113 of printing cream solder in accordance with the first embodiment. As shown inFIG. 2 , cream-solder printing step 113 followsflux application step 111. Instep 113,cream solder 107 is printed onland pattern 104 b, to which resistor 106 (shown inFIG. 5 ) is to be mounted, withsqueegee 132 andscreen 131.Cream solder 107 is used as an example of coupling and fixing member for connection.Screen 131 is a metal screen made of stainless steel, andrecess 126 is formed onscreen 131 at a place corresponding toflux 112 applied.Recess 126 preventsflux 112 from adhering toscreen 131 during the printing ofsolder 107. -
FIG. 5 shows a sectional view of the component-embedded PWB instep 114 of mounting electronic components in accordance with the first embodiment. As shown inFIG. 2 , step 114 of mounting the electronic components followsstep 113 of printing the cream solder. Instep 114,semiconductor element 105 andresistor 106 are mounted ontocircuit board 101 at given places by an automatic insertion machine. A plurality of solder bumps 102 are formed in advance onunderside 105 a ofsemiconductor element 105. -
FIG. 6 shows a sectional view of the component-embedded PWB inreflow soldering step 115 in accordance with the first embodiment. As shown inFIG. 2 ,reflow soldering step 115 followsstep 114 of mounting the electronic components. Instep 115,cream solder 107 is heated to a temperature higher than its melting point, so thatcream solder 107 is melted, wherebyresistor 106 is soldered toland pattern 104 b, and bumps 102 ofsemiconductor element 105 are soldered toland pattern 104 a. In this embodiment,reflow soldering step 115 is carried out in nitrogen atmosphere, thereby preventing the surface ofcircuit board 101 from being oxidized. The contact betweenboard 101 and pre-preg 141 a (shown inFIG. 7 ) is thus improved. - After
reflow soldering step 115, in-process items can be washed in a step (not shown) ofwashing circuit board 101, so that residue offlux 112 and solder balls are cleaned. On top of that, O2 asher process and silane coupling process are recommended, because these surface modifying processes improve the contact betweenboard 101 and pre-preg 141 a. - In this embodiment, the reflow soldering is used because of its excellent quality. The reflow soldering allows fixing of the components soldered at given places due to its self-alignment effect, so that components can be accurately fixed to
board 101 and the length of pattern-lines connected to these components becomes a definite value. In other words, when the pattern lines are used as an inductor, the inductance can produce a definitive value, so that a given electrical performance can be expected. This is an important matter for a high-frequency circuit. -
FIG. 7 shows a sectional view of the component-embedded PWB instep 116 of layering pre-pregs in accordance with the first embodiment, andFIG. 8 shows an enlarged view of an essential part of the foregoing component-embedded PWB. As shown inFIG. 2 , in hole-openingstep 117,hole 142 is opened onpre-preg 141 for receivingsemiconductor element 105 andresistor 106 therein. Inpre-pregs layering step 116 followingreflow soldering step 115, pre-preg 141 with the hole is layered oncircuit board 101.Pre-preg 141 is a collective term which includesindividual pre-pregs resin 110 c,substrate 109 a andresin 110 b.Pre-preg 141 b includesresin 110 b,substrate 109 a andresin 110 b.Pre-preg 141 c includesresin 110 b,substrate 109 a andresin 110 d.Pre-preg 141 employssubstrate 109 a made of non-woven fabric and impregnated withepoxy resin 110 c in advance to be unified.Substrate 109 a is used as an example of the resin flow-speed accelerator. - As shown in
FIG. 8 ,pre-preg 141 is layered oncircuit board 101, so that a layered unit, wheresubstrate 109 a, resins 110 b, 110 c and 110 d are layered one after another, is completed oncircuit board 101.Pre-preg 141 has a thickness of approx. 120 μm becausesubstrate 109 a has a thickness of approx. 80 μm and is impregnated withresin 110, thereby increasing the thickness to approx. 120 μm. -
Clearances 144 are reserved between the outer walls ofresistor 106 and inner wall ofhole 142, so that pre-preg 141 with the hole can be layered oncircuit board 101 with ease. - Since
semiconductor element 105 andresistor 106 are mounted onboard 101 by reflow-soldering, the self-alignment effect due to melting ofcream solder 107 allows mounting of these elements at given places accurately. In other words,clearances 144 can be reduced in size becausesemiconductor element 105 andresistor 106 are mounted precisely, which allowsresin 110 to flow intospaces clearances 144 take the maximum value of approx. 0.2 mm, so that even ifresistor 106 is mounted deviating from a predetermined place,pre-preg 141 can be layered free from inconveniences such as collision. -
Individual pre-pregs 141, which are impregnated withresin substrate 109 a. Thus hole 142 can be opened simultaneously throughsubstrate 109 a andresin 110 b, so that excellent productivity can be expected. There is no need to layersubstrate 109 a andresin 110 individually, so that the number of layering processes can be reduced, which also improving the productivity. - On the upper most face of
pre-preg 141, pre-preg 141 d having nohole 142 is placed, andcopper foil 145 is provided on the entire top face ofpre-preg 141 d. Inlayering step 116,resin 110 c of approx. 20 μm thickness,substrate 109 a of approx. 80 μm, andresin 110 b of 40 μm thickness are layered in this order from the bottom oncircuit board 101. Between theuppermost substrate 109 a andcopper foil 145,resin 110 d of approx. 20 μm thickness is layered. -
Pre-preg 141 d andcopper foil 145 are used in this embodiment; however, a hardened circuit board can be used instead. Any hardened circuit-board such as a single-sided board, double-sided board, or multi-layer board can be used. Use of the hardened circuit board can reduce a warp ofpre-preg 141 caused by thermal contraction in a cooling step described later. - Since there is a small space between
semiconductor 105 andresistors 106, only onehole 142 that accommodates all of a plurality of electronic components is provided. When there are enough spaces between respective electronic components, plural holes can be prepared for accommodating each one of the components respectively. In this case, however, clearances should be provided between the hole and the respective components so that pre-preg 141 can be mounted. A depth of each hole can be changed in response to a height of the respective components. These preparations reduce a cubic volume to which the resin is to be embedded, so that the resin can reach every nook and cranny. - In
unifying step 118,circuit board 101 layered instep 116, pre-preg 141 andcopper foil 145 undergo heating and pressing at a temperature slightly lower than the melting point ofsolder 107, so that they are unified together. Step 118 is described hereinafter following the sequence of the steps shown inFIG. 2 . -
FIG. 9 shows a sectional view of a unifying device used in the unifying step in accordance with the first embodiment. The unifying device includesplatens circuit board 101 is mounted onplaten 152.Platens expandable walls 153 on both sides form air-tight container 154. A sucking device (not shown) is coupled toairtight container 154.Heaters 160 are embedded inplatens heating pre-preg 141. - Between
driver 162 andplaten 152,speed reducer 163 is placed.Speed reducer 163 converts rotary motion into reciprocating motion, and also reduces the rotating speed. A control circuit (not shown) is coupled todriver 162 andheater 160, and controls the timing that operates these two elements. Sinceresin 110 changes in viscosity in response to temperatures, the temperature ofheater 160 is controlled in order to obtain a given viscosity ofresin 110. -
Unifying step 118 using the foregoing unifying device is detailed hereinafter.FIG. 10 shows a schematic sectional view of the unifying device employed in an evacuating step in accordance with the first embodiment. As shown inFIG. 2 , the first step in unifyingstep 118 is evacuatingstep 119 which followspre-preg layering step 116. In evacuatingstep 119, the component-embedded PWB of which pre-preg 141 is layered oncircuit board 101 is housed in air-tight container 154.Platen 151 is fixed andplaten 152 is movable. - A sucking device sucks the air in
airtight container 154 throughvent hole 155 opened throughplaten 152, so thatairtight container 154 is decompressed to a substantially vacuum condition. At this time, it is important to decompress the inside ofhole 142 to a substantially vacuum condition, which allowsresin 110 inpre-preg 141 to be charged intohole 142,spaces 156 betweencircuit board 101 andsemiconductor 105, andspace 157 betweencircuit board 101 andresistor 106 in every nook and cranny in forcible flow-instep 122 described later. The width ofspace 156 ranges from approx. 20 μm to approx. 350 μm, and the width ofspace 157 ranges from approx. 10 μm to approx. 40 μm. - In order to simplify the description, one
semiconductor element 105 and tworesistors 106 are used as examples of electronic components in this embodiment; however, more electronic components are actually mounted oncircuit board 101. Considering the productivity of the component-embedded PWB, a greater size ofcircuit board 101 is preferable, and therefore,more clearances 144 andspaces - In evacuating
step 119, it is thus important to completely suck the air existing in thesenumerous clearances 144 andspaces step 116, board-like pre-pregs 141 having no viscosity at a room temperature, i.e. solid pre-preg, are layered one after another in order to resist the occurrence of voids. Then in evacuatingstep 119,hole 142 is evacuated before pre-preg 141 is softened. These preparations allow the air inhole 142 to be sucked therefrom before pre-preg 141 becomes liquid and has viscosity, in which status, pre-pregs 141 adhere to each other, orpre-preg 141 adheres tocircuit board 101. Evacuatingstep 119 is preferably completed at the latest before the temperature ofpre-preg 141 rises to the glass transition point, so that the air in the spaces betweenrespective pre-pregs 141 and the space betweenpre-preg 141 andcircuit board 101 can be sucked completely therefrom. As a result,clearances 144 andspaces - In this embodiment,
heaters 160 start working to heatplatens step 119, anddriver 162starts driving platens 152, so that a given pressure is applied to the component-embedded PWB. This preparation shrinksexpandable walls 153, so thatplaten 152 is raised along arrow mark A as shown inFIG. 9 . Then as shown inFIG. 10 ,circuit board 101, layeredpre-preg 141 andcopper foil 145 are compressed completely betweenplatens Heaters 160 work at approx. 110° C., and a pressure of approx. 40 kg/cm2 is used. -
FIG. 11 shows a sectional view of the unifying device used in a softening step in accordance with the first embodiment. As shown inFIG. 2 , evacuatingstep 119 is followed by heating andsoftening step 120.Pre-preg 141 starts to be heated whenplatens circuit board 101 andcopper foil 145 through evacuatingstep 119.Resin 110 impregnated intopre-preg 141 is softened by the heat fromheater 160.Resin 110 is heated up to approx. 110° C., and its viscosity is lowered to approx. 2400 pa·s. -
Pre-preg 141 is compressed byplatens copper foil 145. The heat fromheater 160 can thus be positively transferred to pre-preg 141, so that a heating device excellent in energy efficiency and in saving energy is obtainable. -
FIG. 12 shows a sectional view of the unifying device in the forcible flow-in step in accordance with the first embodiment. As shown inFIG. 2 , heating andsoftening step 120 is followed by forcible flow-instep 122, in whichrespective pre-pregs 141 are compressed into the thickness of approx. 90 μm. At this time, resins 110 b, 110 c, 110 d of pre-pregs 141 flow alongsubstrate 109 a in the direction of arrow mark B (shown inFIG. 8 ), and flows intohole 142.Eventually clearances 144,spaces resins resin 110. - In order to increase the flow-speed of
resin 110, the viscosity ofresin 110 is preferably kept at a low level for the longest possible period. For this purpose, it is important to giveresin 110 a viscosity which turnsresin 110 fluid as quick as possible. In heating andsoftening step 120, the temperature ofpre-preg 141 is thus raised at a rate of 4.5° C./minute. On top of that, in forcible flow-instep 122, pre-preg 141 is kept at 110° C. for 30 minutes and is compressed by the pressure of 40 kg/cm2. - These preparations lower the viscosity of
pre-preg 141 quickly to a low enough level for the resin to start flowing in 15 minutes after the heating starts. In 25 minutes after the heating starts, the viscosity becomes the lowest level, i.e. approx. 1500 pa·s. The temperature of 110° C. is maintained for 50 minutes after the heating starts. As discussed above, the lowest viscosity is preferably maintained as long as possible, and for this purpose, the viscosity ofresin 110 is lowered as quick as possible, so thatclearances 144,spaces - Since
platens sandwich circuit board 101 and pre-preg 141 in the vertical direction before they are heated in heating andsoftening step 120,circuit board 101 and pre-preg 141 are heated unevenly depending on the locations ofheaters 160 embedded inplatens board 101 and pre-preg 141 due to this uneven heat. In general,spaces platens Spaces resin 110. Ifresin 110 flows intospaces resin 110 andspaces resin 110 a, namely a tip of the resin flow, lowers. As a result,resin 110 a flowing intospaces resin 110 a does not move halfway of the spaces in forcible flow-instep 122. This problem invites insufficient fill-up of the resin into the spaces, so that voids tend to occur. - The first embodiment thus keeps the temperature of 110° C. for approx. 30 minutes in forcible flow-in
step 122, so that the temperatures ofspaces resin 110 become uniform, thereby preventingresin 110 from stopping its flow into the spaces caused by the temperature decrease. The movement ofplaten 152 is stopped bystopper 161. - After
spaces resin 110, heating and hardeningstep 123 hardensresin 110. Instep 123, pre-preg 141 is heated to a temperature lower than a liquidus temperature ofsolder bump 102 andsolder 107, so that pre-preg 141 loses its fluidity and is completely hardened. In the meantime, at the liquidus temperature, solder becomes liquid completely by heating. - In heating and hardening
step 123, it is important to heat pre-preg 141 so that it becomes hardened and loses its fluidity at a temperature lower than the liquidus temperature ofsolder bump 102 andsolder 107.Solder bump 102 andsolder 107 employ lead-free solder that has a melting point of approx. 270° C., so that the temperature at whichresin 110 loses its fluidity is preferably set not higher than 200° C. instep 123. In this embodiment,step 123 employs a pressure of 40 kg/cm2 so thatresin 110 can lose its fluidity at approx. 150° C. The viscosity ofresin 110 at this time is approx. 24000 pa·s. - As discussed above, heating and hardening
step 123 makesresin 110 lose its fluidity completely, and then raises the temperature ofresin 110 to 200° C. for hardeningresin 110. Sinceresin 110 loses its fluidity at approx. 150° C. instep 123, connection betweensemiconductor 105 andcircuit board 101, or connection betweenresistors 106 andboard 101 never comes off. - After pre-preg 141 is hardened, the step moves on to cooling
step 124, where moderate cooling is slowly carried out. The component-embedded PWB sandwiched byplaten 151 andplaten 152 is slowly cooled by controlling the temperature ofheaters 160. This cooling is done until the temperature reaches not higher than the glass transition point (160° C. by TMA measuring method). Then water is poured intoplatens copper foil 145 andresin 110 caused by different coefficients of linear expansion of these two elements. As a result, warping of the component-embedded PWB can be reduced, and conductors onboard 101 are prevented from peeling off fromresin 110 at their interface. -
FIG. 13 shows a sectional view of a cutting device in cuttingstep 125 in accordance with the first embodiment. Cuttingstep 125cuts resin 172 flowing out to the outside ofcircuit board 101 through forcible flow-instep 122. Instep 125, the component-embedded PWB is cut by rotating dicingteeth 171, which cuts not onlysurplus resin 172 but also both ofcircuit board 101 andresin 172. Becausecircuit board 101 is cut inside the edge, the size of the component-embedded PWB becomes approx. a definite size regardless of expansion or contraction ofcircuit board 101. - As discussed above, in unifying
step 118, heating andsoftening step 120 sharply heats the resin to be fluid, and heating and compressingstep 118 a suppresses a temperature rise applied to pre-preg 141 as well ascircuit board 101 and maintains the temperature. Step 118 a compresses pre-preg 141 at the temperature maintained so thatcircuit board 101 is unified withpre-preg 141 for completingcomponent embedding layer 108. Meanwhile, step 118 a includes heating andsoftening step 120 and forcible flow-instep 122. - In
unifying step 118,resin 110 flows intospaces resin 110 is described with reference toFIG. 14 . -
FIG. 14 shows viscosity characteristics ofresin 110 measured by a viscosity tester.Lateral axis 201 represents temperatures,vertical axis 202 represents viscosity. InFIG. 14 ,curve 203 shows the viscosity on the assumption that the temperature rises at a given rate both insteps Curve 204 shows viscosity characteristics on the assumption that the temperature rises more moderately in forcible flow-instep 122 than in heating andsoftening step 120. - In the case of
curve 203, i.e. in the case where the temperature rises at a given rate both insteps step 122,resin 110 becomes resistant to flow intospaces - On the other hand, in the case of
curve 204, i.e. instep 122 the temperature rises more slowly or steadily, and instep 120 the temperature rising speed becomes faster proportionately, the viscosity lowers by a greater amount, and the minimum viscosity becomes smaller. - In the case of
curve 204,resin 110 is not viscous at room temperature, and it becomes softer and lowers its viscosity as the temperature rises. Attemperature 206, the viscosity reachesminimum viscosity 207, and it increases as the temperature rises fromtemperature 206, so that the hardening ofresin 110 is quickened. Whentemperature 206 is approx. 133° C.,minimum viscosity 207 ofresin 110 becomes approx. 1150 pa·s. - The fluidity of
resin 110 is determined by a pressure applied toresin 110 and a viscosity, or a temperature ofresin 110. For instance, as discussed in this first embodiment, when platen 152 applies a pressure of 40 kg/cm2,resin 110 attains a status of flow-start viscosity 217 at whichresin 110 starts flowing attemperature 211. In other words,resin 110 keeps a board-like status at a temperature ranging from room temperature to temperature 211 (first temperature range 213) and does not flow. Whenresin 110 receives the pressure of 40 kg/cm2, flow-start viscosity is 24000 pa·s, andtemperature 211 at this time is approx. 90° C. - Next, when the temperature exceeds
temperature 211, the viscosity ofresin 110 lowers tominimum viscosity 207 attemperature 206. Forcible flow-instep 122 is thus carried out in temperature range 214 (second temperature range) ranging fromtemperature 211 totemperature 206. - When
step 122 is ended,resin 110 is hardened in heating and hardeningstep 123, in which platen 152 keeps applying the pressure of 40 kg/cm2.Epoxy resin 110 starts hardening gradually when its temperature falls within temperature range 215 (third temperature range) exceedingtemperature 206, and its viscosity reaches flow-start viscosity 212, where it loses the fluidity, attemperature 216. Under the pressure applied in this embodiment,resin 110 loses its fluidity at 150° C., where its viscosity is 24000 pa·s. - As discussed above, setting of the temperatures, such as a smaller temperature-rise in forcible flow-in
step 122 than that in heating andsoftening step 120, and the temperature instep 122 falling between temperature 211 (flow-start viscosity 217) and temperature 206 (minimum viscosity 207), can obtain the following advantage:Resin 110 can maintain its viscosity, which allowsresin 110 to flow intospace 156 with ease at a specified pressure, for a long time. As a result,resin 110 is moved forcibly by pressure, so thathole 142 andspace 156 are positively filled up withresin 110. - The flow of the epoxy resin into
space 156 is demonstrated with reference toFIG. 15 andFIGS. 16A-16C .FIG. 15 shows an enlarged view ofsemiconductor element 105 in the forcible flow-in step in accordance with the first embodiment.FIG. 16A-16C show characteristics inunifying step 118 in accordance with the first embodiment. -
FIG. 10 showsresin 110 prior to compression, andresin 110 becomes fluid due to the compression byplaten 152, and then its tip, namely,resin 110 a, flows intospace 156. At this time,space 156 is so much smaller thanclearance 144 thatresin 110 a can be considered viscous fluid passing through a thin tube. Therefore,eddy 221 occurs nearcorner 105 b, thereby inviting pressure loss. - The presence of
solder bump 102 allowsresin 110 to be considered viscous fluid passing through a thick tube after passing through the thin tube. In other words,resin 110 passing nearsolder bump 102 passes through thin tubes and thick tubes repeatedly, which invites a large amount of pressure loss, so that the flow speed ofresin 110 slows down. It is important to increase the flow speed ofresin 110 as much as possible so as not to stop the flow ofresin 110. - To achieve this objective, the present invention provides fluid-
resin embedding section 108 a withsubstrate 109 a made of glass woven fabric, and a cross sectional area through whichresin 110 flows is reduced in the area wheresubstrate 109 a exists. This preparation allowsresin 110 to resist moving withinsubstrate 109 a along arrow mark B show inFIG. 8 . Sincepre-preg 141 hashole 142, the compressing force in unifyingstep 118 is concentrated tosubstrate 109 a andresin 110. On top of that,compressed resin 110 flows through a space having a small sectional area and sandwiched betweensubstrates 109 a. This mechanism allowsresin 110 to flow at a higher speed with respect to a compressed amount (or a compressing pressure) byplaten 152. As a result, inertia force generated by a flow-speed ofresin 110 becomes greater than viscous force ofresin 110, so that the flow-speed ofresin 110 is considered to be accelerated. As a result, the flow-speed ofresin 110 becomes greater, so thatresin 110 flows intoclearance 144 andspace 156 more positively. - The relation between temperatures and pressures in
unifying step 118 in accordance with the first embodiment is detailed with reference toFIGS. 16A-16C .FIG. 16A shows relations between time, resin temperature and resin viscosity,FIG. 16B shows relation between time and pressure, andFIG. 16C shows relation between time and degrees of vacuum. In these drawings,lateral axis 231 represents the time (minutes), and firstvertical axis 232 represents the temperature (° C.) and secondvertical axis 233 represents the viscosity (pa·s) ofFIG. 16A .Vertical axis 234 ofFIG. 16B represents the pressure (kg/cm2), andvertical axis 235 ofFIG. 16C represents the degree of vacuum (torr). - As shown in
FIG. 16C , it is assumed that degree ofvacuum 237 is achieved attime 236 in evacuatingstep 119. To be more specific,time 236 spans approx. 4 minutes, and degree ofvacuum 237 is approx. 37 torr. At the same time, the pressure starts being applied topre-preg 141, and the pressure reaches the specified value of 40 kg/cm2 in one minute.Heaters 160 start heating simultaneously. - In
FIG. 16A ,curve 238 shows the temperature ofpre-preg 141, andcurve 239 shows the viscosity ofresin 110. In heating andsoftening step 120 after evacuatingstep 119, the temperature is raised totemperature 240 in order to makeresin 110 fluid.Temperature 240 is approx. 90° C. in this embodiment, andresin 110 is heated at a rate of approx. 4.5° C./minute so that the temperature reachestemperature 240 in approx. 15 minutes, and the viscosity lowers toviscosity 248. The viscosity ofresin 110 used in this embodiment becomes approx. 24000 pa·s at 90° C., andresin 110 starts flowing at this viscosity with respect to the pressure of 40 kg/cm2 applied byplaten 152. - Forcible flow-in
step 122 is carried out after the viscosity ofresin 110 is lowered to a fluid level instep 120. Instep 122, the temperature is further raised totemperature 241 whilepressure 249 continues to be supplied, andtemperature 241 is maintained for approx. 30 minutes to allowresin 110 to forcibly flow intospace 156. Instep 120, it is preferable to heatresin 110 as quick as possible so that the viscosity lowers to not higher thanviscosity 248, and instep 122, it is preferable to maintain the temperature ofresin 110 attemperature 241. These operations allow delaying the progress of thermosetting reaction ofresin 110 and maintaining the viscosity at a low level for a long period. - The foregoing operations allow
resin 110 to stay in fluid status even 30 minutes after the viscosity passes acrossviscosity 248, andpressure 249 allowsresin 110 to positively flow intospace 156.Temperature 241 is approx. 110° C., andviscosity 242 is approx. 3550 pa·s. - A pressure applied to
resin 110 at the start of being fluid is preferably greater than that applied upon losing its fluidity, because a greater pressure produces a greater flow-speed ofresin 110 flowing intoclearance 144 andspace 156, which are thus positively filled withresin 110. -
Pre-preg 141 layered inlayering step 116 is provided withclearance 144 around or abovesemiconductor element 105 andresistor 106. To be more specific, the pressure applied fromplaten 152 inunifying step 118 a is concentrated to pre-preg 141 at its face 146 (shown inFIG. 8 ) excepthole 142, so thatresin 110 receives a pressure greater than the pressure supplied fromplaten 152. -
Hole 142 is not prepared forsemiconductor element 105 andresistor 106 individually, but it is prepared for surrounding all these elements, so thathole 142 occupies almost a half area ofboard 101. As a result, pressure as much as twice of the pressure (40 kg/cm2) supplied fromplaten 152 can be applied toresin 110, namely 80 kg/cm2 is applied toresin 110. This mechanism allowsresin 110 to become fluid at a greater viscosity (or a lower temperature) than flow-start viscosity 212, so that a fluidable period can be prolonged. In forcible flow-instep 122,resin 110 can be positively charged intoclearance 144 andspace 156 with more ease. - Heating and hardening
step 123 follows forcible flow-instep 122 wherespace 156 is filled up withresin 110. Instep 123, the temperature ofresin 110 is raised overtemperature 245 at whichresin 110 loses it fluidity underpressure 249, so thatresin 110 becomes non-fluid, i.e. does not move in the least. In this embodiment, the viscosity at whichresin 110 loses it fluidity underpressure 249 is almost the same asviscosity 248 at which the fluidity starts working, so that the viscosity is approx. 24000 pa·s. In heating and hardeningstep 123, the temperature ofresin 110 is raised to 200° C., andresin 110 is kept at this temperature for approx. 60 minutes to be hardened completely. - Use of the method of manufacturing the component-embedded PWB discussed above allows the flow-speed of
resin 110 to be faster by providingsubstrate 109 a, so thatresin 110 can flow intospaces semiconductor element 105,resistor 106 andcircuit board 101 with ease. This manufacturing method thus allows chargingresin 110 positively into the spaces betweensemiconductor element 105,resistor 106 andcircuit board 101 without using any intermediate members. This method does not require putting intermediate members intospaces semiconductor element 105,resistor 106 andcircuit board 101. Inunifying step 118, pre-preg 141 andcircuit board 101 are unified together, and at the same time,spaces resin 110. The present invention thus can provide the forgoing method of manufacturing the component-embedded PWB. - The foregoing method does not need a step of putting intermediate members or the intermediate members per se, so that an inexpensive component-embedded PWB is obtainable. Further, in forcible flow-in
step 122,small spaces resin 110, so that few voids occur and a reliable component-embedded PWB is obtainable. - Complete fill-up of
clearance 144,spaces resin 110 allows supplying the pressure fromplaten 152 both to face 146 (shown inFIG. 8 ) and the resin charged intohole 142, so that a greater area of the resin receives the pressure, and as a result,resin 110 receives a smaller pressure. In this embodiment, the pressure received becomes half. The presence ofhole 142 havingclearance 144 with respect tosemiconductor element 105 andresistor 106 can advantageously prolong the fluid period ofresin 110. On top of that, the pressure supplied to platen 152 can be reduced when the resin starts being fluid, so that the driver can be downsized, which makes the device smaller and inexpensive. - In this embodiment,
platen 152 can apply a pressure of as much as 40 kg/cm2 for compressing because of the following structure: In layeringstep 116, pre-preg 141 is layered such thathole 142 exists oversemiconductor element 105 andresistor 106, so thatplaten 152 cannot apply its pressure directly tosemiconductor element 105 orresistor 106. Since the foregoing great pressure can be supplied,resin 110 is positively charged intoclearance 144 andspace 156. - Since
pre-preg 141 is made of thermosetting resin, once it is heated and hardened, it never returns to plastic status even if it is heated again. Thus oncesemiconductor element 105 is sealed byresin 110, it keeps being fixed. The glass woven fabric is impregnated with epoxy resin, so that whenresin 110 becomes fluid in heating andsoftening step 120 and forcible flow-instep 122, pre-preg 141 can keep its shape as a substrate, so that a component-embedded PWB having dimensional accuracy is obtainable. - It is important to
lower temperature 245 ofresin 110, at whichtemperature resin 110 loses its fluidity, lower than the melting point ofsolder 107 underpressure 249. Becauseresin 110 should be hardened beforesolder 107 is melted through the heat application in heating andsoftening step 123. To be more specific,resin 110 stays hardened and coverssolder 107, so thatsolder 107 never flows out when it is melted. This structure improves reliability. - Temperature 246 (shown in
FIG. 16A ) in heating and hardeningstep 123 is kept lower than the melting point ofsolder 107. In other words,solder 107 employs high-temperature solder of which melting point is higher than the temperature maintained instep 123. This preparation allowssolder 107 not to be melted by the heat supplied fromstep 123, so that a more reliable component-embedded PWB is obtainable. - The temperature maintained in the forcible flow-in step is low enough (e.g. 150° C.) not to melt the solder which connects and fixes
semiconductor element 105 andresistors 106, and yetcircuit board 101 and pre-preg 141 are unified together at the temperature maintained. This unification thus does not break the connection or the fixation. As a result,semiconductor element 105 andresistor 106 can be kept in strong connection and fixation. -
Semiconductor element 105 andresistor 106 are mounted oncircuit board 101, so that an inspection can be carried out for thiscircuit board 101 with the components mounted. As a result, a non-defective rate after completing the component-embedded PWB can be improved. - In this embodiment, a plurality of
pre-pregs 141 are layered one after another; however,substrates 109 a can be layered independently and resins 110 can be layered also independently. In such a case, the flow-speed ofresin 110 can be changed appropriately in response to a thickness of the component-embedded PWB. - In forcible flow-in
step 122, as shown inFIG. 16A , overshootingtemperature range 247 which temporarily exceedstemperature 241 is provided. This preparation allows the temperature in heating andsoftening step 120 to rise more quickly, so that the viscosity ofresin 110 lowers quickly. Thus the low viscosity can be kept for a long period in forcible flow-instep 122, and the fluidity ofresin 110 can be improved. The highest temperature in overshootingtemperature range 247 is 115° C., and this highest temperature is preferably set lower than temperature 244 (125° C. in this embodiment) at whichresin 110 starts being hardened by the pressure supplied. - In
layering step 116, the amount ofresin 110 to be layered oncircuit board 101 should be a greater amount than a fill-up amount of the resin charged intoclearance 144, andspaces pre-preg 141 has dispersion in thickness,substrate 109 a has dispersion, or the condition such as pressure or temperature has dispersion,clearance 144 andspaces resin 110. However, if too much resin is supplied, a large amount ofresin 110 sticks out wastefully to the outside ofboard 101. To overcome this possible problem, this embodiment usessubstrate 109 a, which accelerates the flow-speed ofresin 110, so thatclearance 144 andspaces resin 110 leaving as little as possible left over. - The surplus supply of
resin 110 sometimes increases the resin pressure inclearance 144 andspaces unifying step 118 a, and the resin pressure remains as stress, which generates warp. If the stress becomes excessive, it can damage the components. To overcome this possible problem, the compression to be done inunifying step 118 a should be carried out such that resin layers 110 can be formed betweensubstrate 109 a andboard 101, betweensubstrates 109 a themselves, and betweensubstrate 109 a andcopper foil 145. Such compression allowsresin 110 supplied excessively to flow toward the outside ofboard 101 with ease. - In other words, solid contact is not allowed between
substrate 109 a andboard 101, betweensubstrates 109 themselves, and betweensubstrate 109 a andcopper foil 145. Thus whensubstrate 109 a is compressed, surplus resin passes through theseresin layers 110 toward the outside ofboard 101. This structure allows the resin pressure inclearance 144 andspace 156 to increase by a smaller amount in unifyingstep 118 a, so that warp or damage to the component rarely occurs. - As discussed above, substrate-included
resin section 109 is formed by layeringplural substrates 109 a andplural resins substrate 109 a is used as an example of the resin flow-speed accelerator, and both ofresins resin 110 is prolonged or a pressure applied toresin 110 is changed in response to the heating condition. As a result,resin 110 flows intohole 142 with ease, so that the spaces betweensemiconductor element 105 andresistor 106 can be filled up thoroughly with the resin without providing, for example, a substrate which is conventionally disposed betweensemiconductor element 105 andresistor 106. The complete fill-up of the spaces with the resin allows coveringsemiconductor element 105 andresistor 106 with the resin, so that these two components are insulated from each other. As a result, the space between these two components can be reduced, and a highly dense mounting of electronic components can be expected, which allows downsizing of the component-embedded PWB, and a module employing this PWB can be also advantageously downsized. - The second embodiment of the present invention is demonstrated hereinafter with reference to
FIGS. 17-20 .FIG. 17 shows a flowchart illustrating the steps of manufacturing a component-embedded printed wiring board (PWB) in accordance with this second embodiment. InFIGS. 17-20 , similar elements to those shown inFIGS. 1-12 have the same reference marks, and the descriptions thereof are simplified here. In the first embodiment previously discussed, six sheets ofpre-pregs 141 are layered oncircuit board 101; however, in this embodiment, only one sheet of pre-preg having a thickness of approx. 1 mm is layered oncircuit board 101. The respective steps are detailed hereinafter following the sequence of the steps shown inFIG. 17 . - In this second embodiment, as the first embodiment demonstrates,
semiconductor element 105 andresistor 106 are mounted oncircuit board 101, and they undergo the soldering inreflow soldering step 115. Afterstep 115, hangingstep 300 is prepared for hanging pre-preg 302 overcircuit board 101. Hangingstep 300 is followed by decompressing andlayering step 301.Pre-preg 302 is used as an example of a sheet. - Hanging
step 300, and decompressing andlayering step 301 are demonstrated with reference toFIGS. 18 and 19 .FIG. 18 shows a sectional view of a hanging device in accordance with the second embodiment.FIG. 19 shows a sectional view of a decompressing and layering device in accordance with the second embodiment. - First, hanging
step 300 is described. InFIG. 18 ,airtight container 311 includesplaten 152, guide 312 surrounding lateral faces ofcircuit board 101,slope 313 disposed to the upper end ofguide 312, andopening 314 existing overguide 312.Airtight container 311 is used as an example of an airtight device, andplaten 152 is used as an example of a compressing device. -
Circuit board 101 is inserted intoguide 312 ofairtight container 311. The clearance betweenguide 312 andboard 101 is approx. 0.5 mm on each side, and guide 312 determines the position ofboard 101. -
Pre-preg 302 is placed such that it coversopening 314.Width 315 ofpre-preg 302 should be greater thanwidth 316 ofguide 312 and yet smaller than openingsize 313 a ofslope 313. Such dimensions allow pre-preg 302 to be hung byslope 313 in hangingstep 300.Copper foil 145 is layered onpre-preg 302. To be more specific,slope 313 hangs pre-preg 302 so that pre-preg 302 cannot touchsemiconductor element 105 orresistor 106 because this hanging-up provides a clearance between the underside ofpre-preg 302 and the top face ofsemiconductor element 105 orresistor 106.Slope 313 thus works as a hanging device. -
Pre-preg 302 used in this second embodiment employsepoxy resin 317 in a liquid state, i.e. having a viscosity, at a room temperature, because quicker lowering in viscosity needs less heating, so that a component-embedded PWB can be produced with less energy.Tip 302 a ofpre-preg 302 thus closelycontacts slope 313, so that an airtight space is formed byplaten 152, guide 312,slope 313 andpre-preg 302. In other words, pre-preg 302 per se works as a lid ofairtight container 311.Epoxy resin 317 can be replaced with thermosetting resin such as unsaturated polyester resin. - A sucking device (not shown) sucks the air from the airtight space covered with
pre-preg 302 working as a lid throughvent hole 318 provided to guide 312. Decompressing the airtight space makes the inside ofcontainer 311 negatively pressurized, so that pre-preg 302 lowers alongslope 313 and guide 312. - In this second embodiment, vent
hole 318 is provided near the lower end ofguide 312, and it is preferable to providehole 318 at a place lower thanpre-preg 302 is supposed to sink through decompression. This structure prevents pre-preg 302 from coveringvent hole 318 when the air is sucked throughvent hole 318, so thatcontainer 311 can be evacuated positively. -
FIG. 19 shows a sectional view of a decompressing and layering device in accordance with the second embodiment. As shown inFIG. 19 ,pre-preg 302 stops lowering when it touchestop face 105 c of the semiconductor element ortop face 106 a of the resistor, so that pre-preg 302 is layered overcircuit board 101.Pre-preg 302 is thus held in a negatively pressurized status due to the evacuating. - Evacuating the airtight container leaves no bubbles containing air between
pre-preg 302 andsemiconductor element 105 orresistor 106, so that more solid contact can be expected betweenpre-preg 302 andtop face 105 c ofelement 105 ortop face 106 a ofresistor 106. As a result, a reliable component-embedded PWB is obtainable. -
FIG. 20 show a sectional view of a unifying device to be used inunifying step 303 which follows the compressing and layering step in accordance with the second embodiment. Inunifying step 303,upper platen 321 heats, compresses, and cools pre-preg 302, thereby chargingepoxy resin 317 intospaces unifying circuit board 101 and pre-preg 302 together. - The first step of unifying
step 303 is heating andsoftening step 304 which follows decompressing andlayering step 301. Instep 304,heaters 160 provided toplaten 152 andupper platen 321 apply heat to pre-preg 302 so that pre-preg 302 is softened to be fluid. Sincepre-preg 302 employs fluid material at a room temperature, step 304 needs less heat, i.e. energy can be saved. - In forcible flow-in
step 305 followingstep 304,epoxy resin 317 flows in as it does in the first embodiment. In this second embodiment, it is also important to move platen 321 in order to preventepoxy resin 317 flowing intospaces step 305,epoxy resin 317 is forcibly charged intospaces spaces Epoxy resin 317 starts hardening at a temperature ranging from 110° C. to 150° C. This embodiment usesepoxy resin 317 that starts a thermosetting reaction when the resin is held for approx. 10 minutes in the foregoing temperature range. - In this second embodiment,
pre-preg 302 does not have a hole, so thatspaces 331 formed aroundsemiconductor element 105 andresistor 106 are greater thanclearances 143, 144 formed in the first embodiment. Thus the temperature in forcible flow-instep 305 is set at 100° C., thereby chargingepoxy resin 317 positively intospaces - Step 305 is followed by heating and hardening
step 306. Instep 306,epoxy resin 317 is heated to 150° C. to be completely hardened, and then hardenedresin 317 is cooled gradually in coolingstep 124 and is cut in cuttingstep 125 followingstep 124. - In the second embodiment, it is also important to set a temperature rising rate in
step 305 smaller than that instep 304. This preparation allows lowering the viscosity ofpre-preg 141 quickly and minimizing the viscosity, so that the resin is positively charged into the spaces instep 305. - Compressing and
layering step 301 is carried out ahead ofunifying step 303, so that no bubbles containing air remain between pre-preg 302 andsemiconductor element 105 orresistor 106, and more solid contact can be expected betweenpre-preg 302 andtop face 105 c ofsemiconductor element 105 ortop face 106 a ofresistor 106. As a result, a reliable component-embedded PWB is obtainable. -
Pre-preg 302 does not need a hole corresponding tosemiconductor element 105 andresistor 106 as it is needed in the first embodiment, so that hole-openingstep 117 in the first embodiment is not needed here. As a result, an inexpensive component-embedded PWB is obtainable. - In this second embodiment, holes in response to heights of respective components are not needed, so that one sheet of
pre-preg 302 can work sufficiently. Thus only one sheet ofpre-preg 302 is layered, which lowers the cost of the component-embedded PWB. - Further, pre-preg 302 can be just placed over
slope 313, so that layering work can be simplified, which also reduces the cost of the component-embedded PWB. - In addition, vent holes 318 are provided to guide 312, so that the clearance between
board 101 and guide 312 can be narrowed.Guide 312 thus accurately determines the position ofboard 101, and also prevents pre-preg 302 from flowing out to the outside. This structure allowsepoxy resin 317 to flow intospaces resin 317 so as to be free of voids. - In the third embodiment, another instance of the decompressing and layering device described in the second embodiment is demonstrated, and this other device can replace the one used in the second embodiment. The respective manufacturing steps in the third embodiment remain unchanged from those in the second embodiment. Thus only this replaceable decompressing and layering device is described hereinafter.
-
FIGS. 21 and 22 show sectional views of the decompressing and layering device used in the decompressing and layering step in accordance with the third embodiment.FIG. 23 shows a sectional view of the component-embedded PWB in the forcible flow-in step of the third embodiment. In these drawings, elements similar to those used inFIG. 1-FIG . 20 sometimes have the same reference marks, and in such cases the descriptions thereof are simplified. - In
FIG. 21 ,platens expandable wall 153 formairtight container 154.Circuit board 101, on whichsemiconductor element 105 andresistor 106 have been reflow-soldered, is mounted to platen 152 at a given place.Airtight container 154 is used as an example of an airtight device. -
Platen 151 has holdinggadget 401 mounted rotatably on shaft 402, and holdinggadget 401 is urged inward by springs (not shown), thereby pinchingpre-preg 302 at both sides. Holdinggadget 401 andplaten 151hold pre-preg 302 such thatpre-preg 302 confrontscircuit board 101. -
Platen 151 and holdinggadget 401 form a hanging device, thereby preventing pre-preg 302 from touchingsemiconductor element 105 orresistor 106. This structure allows formingclearance 403 between underside ofpre-preg 302 and top face ofsemiconductor element 105 orresistor 106. A sucking device (not shown) sucks the air from the airtight container through vent holes 155, so that the container is decompressed and evacuated, which makescontainer 154 negatively pressurized, thereby raisingplaten 152. -
FIG. 22 shows a sectional view of the decompressing and layering device used in the decompressing and layering step in accordance with the third embodiment. As shown inFIG. 21 , due to the evacuating,pre-preg 302 is halted keeping in touch with the top faces ofsemiconductor element 105 andresistor 106, so that pre-preg 302 is layered over thecircuit board 101.Pre-preg 302 is thus held in negative pressurized status due to the evacuating. - Thus no bubbles containing air remain between pre-preg 302 and
semiconductor element 105 orresistor 106, and more solid contact can be expected betweenpre-preg 302 andtop face 105 c ofsemiconductor element 105 ortop face 106 a ofresistor 106. As a result, a reliable component-embedded PWB is obtainable. -
FIG. 23 shows a sectional view of a unifying device used inunifying step 303. As shown inFIG. 22 , in unifyingstep 303,upper platen 151 heats, compresses, and cools pre-preg 302, thereby chargingepoxy resin 317 intospaces unifying circuit board 101 and pre-preg 302 together. In this case, tip 401 a of holdinggadget 401 stops when it touchesplaten 152. In other words, holdinggadget 401 also works asstopper 161 described in the first embodiment. - In this third embodiment, holding
gadget 401 is placed such that it covers the entire periphery ofpre-preg 302, so that holdinggadget 401 prevents fluidepoxy resin 317 from flowing out to the outside in unifyingstep 303.Epoxy resin 317 thus flows intospaces resin 317. Since less amount ofpre-preg 302 flows out to the outside, the pre-preg can be downsized proportionately, which can reduce an amount ofpre-preg 302, and an inexpensive component-embedded PWB is obtainable. In general, the thermosetting resin cannot be reused once it is hardened, so that the reduction of the amount ofpre-preg 302 can contribute to environmental protection. - When unifying
step 303 ends its operation, holdinggadget 401 moves outward (along the arrow mark shown inFIG. 22 ) for releasingpre-preg 302, so thatplaten 151 can move upward andcircuit board 101 can be taken out. - Compressing and
layering step 301 is carried out ahead ofunifying step 303, so that no bubbles containing air remain between pre-preg 302 andsemiconductor element 105 orresistor 106, and more solid contact can be expected betweenpre-preg 302 andtop face 105 c ofsemiconductor element 105 ortop face 106 a ofresistor 106. As a result, a reliable component-embedded PWB is obtainable. -
Pre-preg 302 does not need a hole corresponding tosemiconductor element 105 andresistor 106 as it is needed in the first embodiment, so that hole-openingstep 117 in the first embodiment is not needed here. As a result, an inexpensive component-embedded PWB is obtainable. - In this third embodiment, holes in response to heights of respective components are not needed, so that one sheet of
pre-preg 302 can work sufficiently. Thus only one sheet ofpre-preg 302 is layered, which reduces the cost of the component-embedded PWB. - Further, pre-preg 302 can be just pinched by holding
gadget 401, so that layering work can be simplified, which also reduces the cost of the component-embedded PWB. - In this third embodiment,
pre-preg 302 is hung; however,circuit board 101 can be hung instead. In such a case, a similar advantage to what is discussed above is also obtainable. - The component-embedded PWB of the present invention includes the following elements:
-
- a fluid-resin embedding section formed at a place corresponding to electronic components and covering the components;
- a resin flow-speed accelerator surrounding the fluid-resin embedding section and being disposed in parallel with a top face of a circuit board; and
- bonding resin disposed between the accelerator and the circuit board.
The embedding section is filled up with the same resin as the bonding resin. The foregoing structure allows the accelerator to compress the resin by a pressure applied when the component-embedded PWB is pressed, so that the resin can flow along the PWB with ease. The resin is thus charged into the fluid-resin embedding section in every nook and cranny, so that no air remains. As a result, the load produced by expanding the air does not damage the connections, so that the quality of the connections improves.
- The component-embedded PWB and the manufacturing method of the same PWB of the present invention can advantageously provide reliable connections in the component-embedded PWB. Use of the same PWB as the boards, on which components are reflow-soldered, is useful.
Claims (4)
1. A component-embedded printed wiring board comprising:
a circuit board;
an electronic component mounted to a top face of the circuit board;
a component embedding layer covering the electronic component and provided to the top face of the circuit board; and
a conductive pattern provided on the component embedding layer,
wherein the component embedded printed wiring board is formed by pressing the circuit board, the component embedding layer, and the conductive pattern together,
wherein the component embedding layer includes:
a fluid-resin embedding section formed at a place corresponding to the electronic component for covering the electronic component;
a resin flow-speed accelerator provided in parallel with the top face of the circuit board and surrounding the fluid-resin embedding section; and
bonding resin disposed between the accelerator and the circuit board, and
wherein the fluid-resin embedding section is filled up with resin identical to the bonding resin.
2. The component embedded printed wiring board of claim 1 , wherein the resin flow-speed accelerator shapes like a board.
3. The component embedded printed wiring board of claim 2 further comprising a substrate-included resin section having a plurality of layers of the accelerators, wherein the substrate-included resin section has a resin layer formed of the bonding resin between the plurality of the accelerators.
4. The component embedded printed wiring board of claim 1 , wherein the accelerator is formed of one of woven fabric and non-woven fabric.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US12/709,573 US20100147569A1 (en) | 2005-05-20 | 2010-02-22 | Component-embedded printed wiring board |
Applications Claiming Priority (4)
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JP2005-147864 | 2005-05-20 | ||
JP2005147864A JP2006324567A (en) | 2005-05-20 | 2005-05-20 | Substrate incorporating component and its manufacturing method |
US11/434,763 US7694415B2 (en) | 2005-05-20 | 2006-05-17 | Method of manufacturing component-embedded printed wiring board |
US12/709,573 US20100147569A1 (en) | 2005-05-20 | 2010-02-22 | Component-embedded printed wiring board |
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US11/434,763 Division US7694415B2 (en) | 2005-05-20 | 2006-05-17 | Method of manufacturing component-embedded printed wiring board |
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US20100147569A1 true US20100147569A1 (en) | 2010-06-17 |
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US11/434,763 Expired - Fee Related US7694415B2 (en) | 2005-05-20 | 2006-05-17 | Method of manufacturing component-embedded printed wiring board |
US12/709,575 Abandoned US20100146779A1 (en) | 2005-05-20 | 2010-02-22 | Method of manufacturing component-embedded printed wiring board |
US12/709,573 Abandoned US20100147569A1 (en) | 2005-05-20 | 2010-02-22 | Component-embedded printed wiring board |
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US12/709,575 Abandoned US20100146779A1 (en) | 2005-05-20 | 2010-02-22 | Method of manufacturing component-embedded printed wiring board |
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CN103098565B (en) * | 2010-09-10 | 2016-08-03 | 名幸电子有限公司 | Substrate having built-in components |
JP5600803B2 (en) * | 2011-05-13 | 2014-10-01 | イビデン株式会社 | Wiring board and manufacturing method thereof |
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KR102139755B1 (en) * | 2015-01-22 | 2020-07-31 | 삼성전기주식회사 | Printed circuit board and method of manufacturing the same |
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US20220368786A1 (en) * | 2019-06-24 | 2022-11-17 | Samsung Electronics Co., Ltd. | Electronic device comprising flexible display |
Also Published As
Publication number | Publication date |
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CN1867224A (en) | 2006-11-22 |
US20060260122A1 (en) | 2006-11-23 |
JP2006324567A (en) | 2006-11-30 |
CN100525580C (en) | 2009-08-05 |
US20100146779A1 (en) | 2010-06-17 |
US7694415B2 (en) | 2010-04-13 |
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