Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
  • H01L23/538—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames the interconnection structure between a plurality of semiconductor chips being formed on, or in, insulating substrates
  • H01L23/5385—Assembly of a plurality of insulating substrates
• • 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
  • H05K1/02—Details
  • H05K1/03—Use of materials for the substrate
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
  • H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
  • H01L21/4814—Conductive parts
  • H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
  • H01L21/4857—Multilayer substrates
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
  • H01L23/538—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames the interconnection structure between a plurality of semiconductor chips being formed on, or in, insulating substrates
  • H01L23/5383—Multilayer substrates
• • 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
  • H05K3/4602—Manufacturing multilayer circuits characterized by a special circuit board as base or central core whereon additional circuit layers are built or additional circuit boards are laminated
• • 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
  • H01L2224/02—Bonding areas; Manufacturing methods related thereto
  • H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
  • H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
  • H01L2224/0554—External layer
  • H01L2224/0556—Disposition
  • H01L2224/05568—Disposition the whole external layer protruding from the surface
• • 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
  • H01L2224/02—Bonding areas; Manufacturing methods related thereto
  • H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
  • H01L2224/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
  • H01L2224/0554—External layer
  • H01L2224/05573—Single external layer
• • 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
  • H01L2924/30—Technical effects
  • H01L2924/301—Electrical effects
  • H01L2924/3011—Impedance
• • 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
  • H05K1/02—Details
  • H05K1/0271—Arrangements for reducing stress or warp in rigid printed circuit boards, e.g. caused by loads, vibrations or differences in thermal expansion
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/01—Dielectrics
  • H05K2201/0183—Dielectric layers
  • H05K2201/0195—Dielectric or adhesive layers comprising a plurality of layers, e.g. in a multilayer structure
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/02—Fillers; Particles; Fibers; Reinforcement materials
  • H05K2201/0203—Fillers and particles
  • H05K2201/0206—Materials
  • H05K2201/0209—Inorganic, non-metallic particles
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/06—Thermal details
  • H05K2201/068—Thermal details wherein the coefficient of thermal expansion is important
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/09218—Conductive traces
  • H05K2201/09236—Parallel layout
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/0929—Conductive planes
  • H05K2201/093—Layout of power planes, ground planes or power supply conductors, e.g. having special clearance holes therein
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/095—Conductive through-holes or vias
  • H05K2201/09536—Buried plated through-holes, i.e. plated through-holes formed in a core before lamination
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/095—Conductive through-holes or vias
  • H05K2201/0959—Plated through-holes or plated blind vias filled with insulating material
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/09654—Shape and layout details of conductors covering at least two types of conductors provided for in H05K2201/09218 - H05K2201/095
  • H05K2201/09781—Dummy conductors, i.e. not used for normal transport of current; Dummy electrodes of components
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09209—Shape and layout details of conductors
  • H05K2201/09654—Shape and layout details of conductors covering at least two types of conductors provided for in H05K2201/09218 - H05K2201/095
  • H05K2201/098—Special shape of the cross-section of conductors, e.g. very thick plated conductors
• • 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
  • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
  • H05K2201/09—Shape and layout
  • H05K2201/09818—Shape or layout details not covered by a single group of H05K2201/09009 - H05K2201/09809
  • H05K2201/09881—Coating only between conductors, i.e. flush with the conductors
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/03—Metal processing
  • H05K2203/0353—Making conductive layer thin, e.g. by etching
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/05—Patterning and lithography; Masks; Details of resist
  • H05K2203/0562—Details of resist
  • H05K2203/0585—Second resist used as mask for selective stripping of first resist
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
  • H05K2203/0756—Uses of liquids, e.g. rinsing, coating, dissolving
  • H05K2203/0759—Forming a polymer layer by liquid coating, e.g. a non-metallic protective coating or an organic bonding layer
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/14—Related to the order of processing steps
  • H05K2203/1476—Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
• • 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
  • H05K3/0011—Working of insulating substrates or insulating layers
  • H05K3/0017—Etching of the substrate by chemical or physical means
  • H05K3/0023—Etching of the substrate by chemical or physical means by exposure and development of a photosensitive insulating layer
• • 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
  • H05K3/0011—Working of insulating substrates or insulating layers
  • H05K3/0017—Etching of the substrate by chemical or physical means
  • H05K3/0026—Etching of the substrate by chemical or physical means by laser ablation
  • H05K3/0032—Etching of the substrate by chemical or physical means by laser ablation of organic insulating material
• • 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

Definitions

• the present invention relates to the use of thin- film deposition technology to create a high speed structure having high density interconnects formed on a conventional printed wiring board substrate. More specifically, the present invention pertains to an improved method for minimizing the effects of accumulated stress between the printed wiring board substrate and overlying deposited thin film layers while maintaining a relatively overall low impedance in the resulting structure. The method of the present invention is also useful for creating interconnections on high density daughter boards that carry packaged devices.
• the semiconductor industry continues to produce integrated circuits of increasing complexity and increasing density. The increased complexity of some of these integrated circuits has, in turn, resulted in an increased number of input/output pads on the circuit chips. At the same time, the increased density of the chips has driven the input/output pad pitch downward. The combination of these two trends has been a significant increase in the connector pin wiring density needed to connect the chips to packages that interface with the outside world and interconnect the chips to other integrated circuit devices.
• PWB printed wiring board
• QFPs quad flat packs
• PWB technology typically uses copper and insulating dielectric material sub- laminates as building blocks to create the required interconnect structures.
• the process of forming a copper conductive pattern on the sub-laminate in PWB technology typically includes forming a dry film of photo resist over the copper layer, patterning and developing the photo resist to form an appropriate mask and selectively etching away the unwanted copper, thereby leaving the desired patterned conductive layer.
• Substrates used in PWB technology can be manufactured in large area panels providing efficiencies that lower the costs of production.
• Interconnect solutions using this technology generally have relatively good performance characteristics because of the copper and low dielectric constant (e.g. less than or equal to 4.0) employed.
• the printed wiring board industry has not kept pace with the advances in semiconductor manufacturing in terms of pad density and pad count. As a result, there is a capability gap between semiconductor manufacturers and interconnect printed wiring board manufactures.
• two or more pieces of laminate are laminated together to form a final structure.
• Interconnection between laminated layers can be provided by through-holes mechanically drilled and then plated. The drilling process is relatively slow and expensive and can require a large amount of board space.
• an increased number of signal layers is often used to form the interconnect structure.
• the conventional printed wiring board technology needs to go to a large number of metal layers (e.g. greater than eight layers) for some of the applications in high density integrated circuit packaging and daughter board fabrication. Utilizing a large number of layers in this context generally increases cost and decreases electrical performance.
• the pad size limits the wiring density on any given layer with this technology.
• PWB technology while useful for some applications, is not capable of providing the connection density required in other applications.
• build-up multi-layer To improve the interconnect density of PWB technology, an advanced printed wiring board technology approach called build-up multi-layer has been developed.
• a traditional printed wiring board core is the starting point.
• Standard drilling and plating techniques form plated through-holes in the core. From the basic core this build-up approach has many variations.
• a dielectric layer approximately 50 microns thick is laminated to both the top and bottom major surfaces of the conventionally fabricated printed wiring board substrate. Vias are made in the buildup layer by laser ablation, photo mask/plasma etch, or other known methods.
• An electrodeless seeding step is then done prior to a panel plating step that metalizes both the upper and lower surfaces. Subsequent masking and wet etching steps then define a desired conductive pattern over the laminated dielectric layers.
• This technology offers a large improvement in terms of density over standard PWB technology without build-up layers; however, such build-up boards require multiple layers in order to meet the developing high density packaging and daughter board requirements. Thus this technology still has limitations.
• MLC technology involves rolling a ceramic mix into sheets, drying the sheets, punching vias, screening the rolled sheets with a metal paste representing the trace pattern on the surface of the ceramic, stacking and laminating all the layers together, then cofiring at a high temperature (e.g. greater than 850 °C) to achieve the desired interconnections.
• a high temperature e.g. greater than 850 °C
• MLC construction has found extensive use in high density and high reliability products where the robustness of the high density interconnect package outweighs the cost considerations.
• the ability to create a hermetic seal in the ceramic improves the ability to withstand environments not tolerable to conventional printed wiring board technology. While this technology is capable of high density packaging applications (e.g. greater than 1000 pads), it is also very costly. Additionally, performance characteristics, such as signal propagation time, are impacted due to the relatively high dielectric constant (e.g. between 5.0 and 9.0) of the ceramic material.
• MLC technology provides higher connection density than PWB technology, but is not capable of providing the connection density required for some of today's high density interconnect applications.
• a third approach which the high density interconnect and packaging industry has moved to addressing these high density interconnect applications using thin film deposition technology is sometimes referred to as deposited on laminate or D L technology in a broad sense, as well as MCM-D or MCM deposition technology in a multichip module context.
• D/L technology includes forming and patterning thin film conductive traces over large substrates such as the laminated printed wiring boards discussed above. Such large substrates may have a surface area of 40 centimeters by 40 centimeters or more, thereby providing efficiencies that lower the costs of production.
• D L technology utilizes a combination of low cost printed wiring board structures, with or without the use of the build-up multi-layers on the printed wiring board, as a starting point to meet the high density and low cost interconnect requirements.
• This combination of existing conventional high volume printed wiring board technology and advanced thin film deposition technology represents a significant economic advantage and density improvement as compared to the previously discussed PWB and MLC technologies.
• D/L technology creates a high interconnect density substrate using thin film processes on only one side of the printed wiring board.
• the high density interconnects are formed by depositing alternating insulating and conducting thin film layers. The total thickness of several of these deposited layers is less than the thickness of a single traditional build-up layer. This eliminates the need for balancing the build-up layers on both top and bottom to prevent warpage of the substrate.
• the D/L process involves first laying down a layer of an insulating dielectric on the top surface of a printed wiring board substrate, depositing a conductive material over the dielectric layer, creating a circuit pattern in the conductive material, then depositing the next insulating and conductive layers.
• the various layers so created are connected through vias constructed using a variety of known techniques such as wet chemical etch, photo expose and develop or laser ablation. In this way a three dimensional deposited laminated structure is achieved enabling high density interconnect patterns to be fabricated in small physical areas.
• Each of these stresses can be a source of failures such as cracking of the dielectric material and cracking and delamination of the conductive material. In either of these cases opens and shorts can destroy the functionality of the completed high density interconnect structure.
• the stresses associated with physical handling can be substantially eliminated through proper design of processes, operator training, and proper fixture design. Stresses related to thermal changes, however, must be minimized through proper design of the high density interconnect structure.
• a problem encountered with increasing the filler content of the dielectric layer is that the dielectric constant is proportional to the amount of filler included in the layer. As a result, the less durable the dielectric layer, the higher the impedance associated with the structure formed with such a layer.
• a method for forming low-impedance high density deposit-on-laminate structures having reduced stress features reducing metallization present on the laminate printed circuit board In this manner, reduced is the force per unit area exerted on the dielectric material that is disposed adjacent to the laminate material which is typically present during thermal cycling ofthe structure.
• the laminate printed circuit board has two opposed major surfaces, and a conductive wiring pattern is formed on one ofthe two opposed major surfaces.
• the conductive wiring pattern typically includes one or more conductive traces. Each conductive trace has at least two sides extending from a common area, defining a junction, transversely to one another. One ofthe two sides terminates proximate to the first surface.
• the method includes reducing an area of one ofthe two sides ofthe conductive trace.
• the area is reduced by increasing the area ofthe junction through a process of abrasion.
• the junction formed thereby defines a right angle.
• Employing abrasion when forming the structure provides the junction with an arcuate profile, increasing the surface area of the junction. The increase in surface area reduces the force per unit area exerted on the dielectric material disposed adjacent to the conductive trace.
• the area of one ofthe two sides ofthe conductive trace is reduced by polishing the conductive wiring pattern to reduce a height ofthe conductive trace, measured from the first major surface, to be within a range of 10 to 20 microns, inclusive.
• the effects ofthe difference in coefficients of thermal expansion between the conductive wiring pattern and the dielectric material is reduced.
• the dielectric material expands and contracts at a greater rate than the conductive wiring pattern.
• the stress in the structure may be reduced in the presence of through-holes extending between the opposed major surfaces.
• through-holes are coated with a conductive material and include an epoxy filler disposed therein.
• the epoxy filler expands and contracts isotropically, it has been found that forces exerted on the conductive material is exerted on conductive traces, resulting in the same causing failures in the dielectric material.
• the epoxy filler is selected to have a coefficient of thermal expansion in the range of 20-25 x 10 "6 / °C.
• Fig. 1 is a cross-sectional view of an exemplary structure formed in accordance with the present invention
• Fig. 2 is a detailed cross-sectional view ofthe circuit shown above in Fig. l;
• Fig. 3 is a further detailed cross-sectional view showing the features of a conductive trace shown in Figs. 1 and 2, above;
• Fig. 4 is a detailed cross-sectional view showing the features of a conductive trace shown in accordance with a prior art structure
• Fig. 5 is a flow diagram of a method employed to form the circuit identified above in Figs. 1, 2 and 3 in accordance with the present invention
• Fig. 6 is a detailed cross-sectional view showing the features of a conductive trace shown in accordance with an alternate embodiment ofthe present invention.
• Fig. 7 is a flow diagram of a method employed to form the circuit identified above in Figs. 1 and 2 in accordance with a second embodiment ofthe present invention.
• DESCRIPTION OF THE SPECIFIC EMBODIMENTS Fig. 1 shows an exemplary deposited-on-laminate (D/L) structure 10 in accordance with the present invention that includes a laminate board 12 having two opposed major surfaces 12a and 12b with a conductive wiring pattern disposed thereon, shown generally as conductive traces 14a and 14b.
• the region ofthe laminate board 12 disposed between the surfaces 12a and 12b is laminate resin insulator 16 that has conductive paths, shown generally as 18a and 18b, embedded therein.
• a through-hole 22 is formed in the laminated board 12, extending through the resin insulator between opposed apertures 22a and 22b positioned in opposed surfaces 12a and 12b, respectively.
• Conductive material 24 is present within the through-hole 22 and conforms to the shape thereof.
• the conductive material forms a hollow cylinder.
• one or more ofthe conductive paths 18a and 18b are in electrical communication with the conductive material 24.
• Disposed adjacent to the surface 12a is a conductive pad 26a that surrounds the aperture 22a.
• Also present on the surface 22b may be another conductive pad 26b, surrounding the aperture 22b.
• the conductive material 24 places the conductive pads 26a and 26b in electrical communication with each other and the conductive paths 18a and 18b.
• the conductive elements ofthe structure 10 may be formed from any conductive or semi- conductive material known, it is preferred that the same be formed from a metallic material, such as copper containing material.
• a build-up dielectric layer 30 Disposed adjacent to the laminate board 12 is a build-up dielectric layer 30 that includes dielectric material 32 positioned adjacent to surface 12a.
• a via 34 is formed in the dielectric material 32 to allow electrical communication between opposing sides of the build-up layer 30.
• a conductive contact 36 is disposed within the via 34 that is in electrical communication with conductive trace 14a.
• an extended laminate layer 40 Disposed adjacent to the build-up layer 30 is an extended laminate layer 40 that includes a plurality of dielectric layers 42 and 44.
• a conductive contact 46 is disposed between layers 42 and 44.
• a via 48 is formed through dielectric layer 42 facilitating electrical connections between conductive contact 46 and a circuit positioned adjacent to the extended laminate layer 40.
• a circuit 50 is in electrical communication with the conductive contact 46 via a solder ball 52 connected to a bond pad 54.
• the circuit 50 is spaced-apart from the extended laminate layer 40, defining a gap 56 therebetween.
• Mechanical support is provided to the circuit 50 having underfill, such as epoxy or some other suitable material, placed in the gap 56.
• a problem solved by the present invention concerned stress failures at the conductive trace/dielectric material interface.
• the stress failures occurring within build-up layer 30 are discussed with the understanding that the present invention can be used to reduce the stress at any conductive material material/dielectric interface. Specifically, it was noticed that cracks formed in the portions ofthe dielectric material located proximate to the conductive traces 14a and 14b, as well as conductive pad 26a, and are shown generally as 60. It is believed that these cracks were the result of the differing coefficients of thermal expansion ofthe material from which the conductive traces 14a and 14b and 22a and the build-up layer 30 are formed. Specifically, the dielectric material build-up layer 30 is formed from dielectric is Nippon Steel Chemical V-259P coated to a maximum thickness of 20 to 30 microns.
• the Nippon Steel Chemical polymer is a photo definable cardo acrylate material and has a coefficient of thermal expansion of approximately 50 x 10 '6 / °C.
• the conductive traces 14a, 14b, as well as conductive pad 22a are formed from a copper containing material.
• the copper containing material is a chrome/copper stack deposited from, for example, a sputtering process as known to those skilled in the art.
• Other copper metallurgy e.g. chrome/copper/chrome or copper/palladium among others
• the coefficient of thermal expansion ofthe copper containing material will be commensurate for that of copper, i.e., approximately 16.5 x 10 "6 /°C. This results in the dielectric material 32 expanding and contracting at a greater rate than the copper containing material.
• the different rates of contraction causes the conductive traces 14a and 14b, as well as the conductive pad 22a, to exert a great amount of force per unit area against the dielectric material 32 when the dielectric material 32 contracts, thereby cracking the dielectric material 32.
• each ofthe conductive traces 14a, 14b and conductive pad 22a has three exposed sides.
• the three exposed sides of conductive trace 14a are shown as 15 a, 15b and 15c. Two ofthe sides, 15a and 15c, extend parallel to each other. Side 15b extends transversely to sides 15a and 15b.
• sides 15a and 15c extend from the surface 12a and terminate proximate to side 15b, forming a junction 15d thereat. It was recognized that the junction 15d is located proximate to the region 60 of failure in the dielectric material 32.
• the present invention reduces the failure in region 60 by providing the junction 15d with an arcuate profile. Specifically, it was recognized that the prior art junctions 115d, shown in Fig. 4, formed a right angle. It was thought that the force per unit area exerted on the region 160 could be reduced by reducing the angle formed the junction 115d. To that end, the area of the junction 15d, shown in Figs. 2 and 3, was increased by providing the same with an arcuate profile. This resulted in a reduction in the area of sides 15a , 15b and 15c. With this structure, reduced is the force per unit area exerted on the dielectric material 32 by the conductive trace 14a, during thermal cycling ofthe structure 10.
• the laminate board 12 is provided with the wiring pattern already disposed thereon.
• the D/L structure 10 is then fabricated as a end user process after fabrication ofthe laminate board 12.
• a vibratory abrading apparatus An example of such a vibratory abrading apparatus is shown in United States Patent No. 4,143,491.
• a receptacle contains an abrading compound. For example, sand with a very fine grain structure that is agitated or oscillated at a predetermined frequency is present in the receptacle.
• the method for forming the D/L structure 10 includes providing the laminate board 12 having a wiring pattern thereon at step 200 and applying an identifier on the laminate board 12 using, among other things, as ablation process.
• a laser may be employed to scribe the board as a function ofthe operation to be performed.
• the laminate board 12 may have any thickness desired.
• the laminate board 12 is a one millimeter thick, measured between the opposing major surfaces 12a and 12b manufactured by Mitsubishi from BT HL810 resin dielectric.
• the wiring pattern consists of conductive traces, shown generally as conductive traces 14a, 14b and conductive pad 22a, having a thickness in the range of 20 to 30 microns.
• the thickness ofthe conductive traces is measured from the surface 12a to, for example, the side 15b ofthe conductive trace 14a.
• the laminate board 12 is placed in a vibratory abrading apparatus, as discussed above, to create the arcuate profile of the junctions ofthe copper conductive traces that comprising the wiring pattern.
• the wiring pattern is cleaned using a standard process known in the art. Specifically, an antioxidant, such is employed that creates an oxide on the surface having a thickness of approximately 1 ,000 angstroms.
• the dielectric material 32 is deposited on the surface 12a via spin coating so as to flow and planarize the wiring pattern adjacent thereto.
• multiple layers may be spun-on to "build-up" the layer 30, as desired.
• two layers of dielectric material 32 are spun-on to provide a thickness in the range of 25 to 50 microns, inclusive.
• an image of a via pattern, such as for via 34 are formed in regions of dielectric material which are developed and the developer subsequently removed.
• the laminate board 12 is then baked at 160 °C for 90 to cure and reflow the dielectric layer 32.
• residue present on the dielectric layer is removed by placing the laminae board 12 in a plasma including oxygen source, such as O 2 , and a fluorine source, such as F 2 .
• the plasma also roughens the surface ofthe dielectric material 32 disposed opposite to surface 12a.
• a wet etch is employed to remove the exposed surfaces ofthe oxide present on the wiring pattern.
• Additional copper is then sputtered onto the laminate board 12, coextensive with the area ofthe surface 12a at step 216.
• all exposed dielectric material 32 is covered with copper approximately 2,000 angstroms thick, forming a seed layer.
• the seed layer may be deposited by a number of different methods as would be known to a person of ordinary skill in the art.
• the seed layer is a chrome/copper stack where the chrome layer is an adhesive layer approximately 200 angstroms thick, and the overlying copper layer is approximately 2000 angstroms thick, with each layer being deposited by a sputtering process.
• the seed layer is patterned by depositing a photoresist layer over the seed layer, exposing selected portions ofthe photoresist to UV light and developing the exposed layer to remove desired portions ofthe photoresist.
• a plating process is employed as step 220 wherein the laminate board 12 is immersed in a plating bath (e.g., in a SFT plating tool manufactured by Technics Corporation) and electrical contact is made to seed layer so that the seed layer acts as a cathode.
• a plating bath e.g., in a SFT plating tool manufactured by Technics Corporation
• electrical contact is made to an exposed area ofthe seed layer on the periphery (i.e., outside the active area) ofthe laminate board 12.
• the laminate board 12 is positioned between two opposing anodes so that material can be plated on both surfaces 12a and 12b. This results in all exposed pads on both surfaces 12a and 12b being are plated.
• the exposed pads on the surface 12a include conductive contact 36. Because the method ofthe present invention utilizes a design rule in which all plated through holes are electrically connected to a conductive pad 36, plating should occur on the bottom pads connected to each plated through hole unless a defect (open) exists in the substrate.
• the photoresist is stripped and the copper etched leaving the wiring pattern desired.
• an electrical test is performed to check the electrical characteristics ofthe wiring pattern.
• the aforementioned steps may be repeated to deposit an additional layer onto the structure 10.
• various visual inspections may be performed during any ofthe aforementioned process steps to detect failures during fabrication.
• junction 160 is shown having an arcuate profile and junction 60 forming a right angle. As shown, the profile of junction 160 results in a reduction in the area ofthe sides 115a, 115b and 115c ofthe conductive trace 114a, compared with the conductive trace 14a shown in Fig. 4.
• the force per unit area exerted on the dielectric material 132 may be further reduced by polishing the wiring pattern on surface 112a ofthe laminated substrate 112.
• the conductive traces on the surface 112a such as conductive trace 114a, has a height, measured from the surface 112a to the side 115b that is reduced in the range of 10-20 microns.
• the area of both sides 115a and 115c are reduced. This was found to greatly decrease the failures in the regions 160 of dielectric material 132.
• the dielectric material 132 in region 160 may be made much thinner and with less filler, thereby providing a lower dielectric constant to the structure and therefore, a lower impedance.
• step 202 is replaced by step 302 in which the wiring pattern on the board is polished by any means known in the art to a height in the range of 10 to 20 microns, inclusive. However, a height of 12 microns is preferred.
• the remaining steps ofthe process of Fig. 7, 300, 304, 306, 308, 310, 312, 314, 316, 318, 320, 322 and 324 are identical to steps 204, 206, 208, 210, 212, 214, 218, 220, 222 and 224, respectively, mentioned above with respect to Fig. 5.
• steps 302 and 202 could be combined in fabricating a common D/L structure 10.
• the method of fabrication would being identical to that discussed above with respect to Fig. 7 and including step 202 shown above in Fig. 5.
• the combining the junction with the arcuate profile, as discussed above would augment the stress reduction achieve by polishing the wiring pattern to the critical height in the range of 10 to 20 microns.
• stress on the dielectric material 32 is reduced by establishing the coefficient of thermal expansion of an epoxy filler disposed within the through-hole 22 to be within a critical range. Specifically, it was found that the stress on the dielectric material proximate to the junction 17 was in part attributable to the expansion of the epoxy filler 23 disposed within the through-hole 22. It is believed that the isotropic nature ofthe expansion ofthe epoxy filler 23 coupled with the thickness ofthe laminate substrate 12 resulted in a great amount of force being exerted on the conductive material 24 disposed within the through-hole. This force is in turn transmitted to the dielectric material 32 causing failure ofthe same.

Applications Claiming Priority (15)

Publications (1)

Family

ID=27568570

Family Applications (1)

Country Status (5)

Families Citing this family (1)

Family Cites Families (3)

• 1999
  • 1999-07-30 AU AU52499/99A patent/AU5249999A/en not_active Abandoned
  • 1999-07-30 KR KR1020017001337A patent/KR20010072144A/ko not_active Application Discontinuation
  • 1999-07-30 JP JP2000562936A patent/JP2003527740A/ja active Pending
  • 1999-07-30 EP EP99937726A patent/EP1114439A2/de not_active Withdrawn
  • 1999-07-30 WO PCT/US1999/017434 patent/WO2000007222A2/en not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events