JP4998274B2 - Manufacturing method of ceramic multilayer substrate - Google Patents

Description

The present invention relates to a method for manufacturing a ceramic multilayer substrate.

Low temperature co-fired ceramics (LTCC) technology enables the simultaneous firing of a green sheet and a metal, so that an element-embedded substrate incorporating various passive elements between ceramic layers can be realized. In the system-on-package (SOP) mounting technology, this element-embedded substrate (hereinafter simply referred to as an LTCC multilayer substrate) is used in order to reduce the parasitic effects that occur in the combination of electronic components and surface-mounted components. The manufacturing method involved has been intensively developed.

In the manufacturing method of the LTCC multilayer substrate, a drawing process for drawing a pattern such as a passive element or a wiring on each of a plurality of green sheets, a crimping process for laminating a plurality of green sheets having the pattern, and a crimping body, A firing step of batch firing is sequentially performed.

In order to increase the density of various patterns in the drawing process, a so-called ink jet method is proposed in which conductive ink is discharged as fine droplets (for example, Patent Document 1). The ink-jet method uses droplets of several picoliters to several tens of picoliters, and enables pattern miniaturization and narrow pitch by changing the ejection position of the droplets.
JP 2005-57139 A

Incidentally, the LTCC multilayer substrate is increasingly required to have a high-frequency wiring structure as the signal processing speed increases. In general, there is an aerial wiring as a wiring structure for high frequency measures. Air wiring is attracting attention as a wiring structure for high frequency countermeasures because of its low dielectric constant.

However, since the LTCC multilayer substrate has a laminated structure of a plurality of green sheets having a pattern, it is difficult to form a low dielectric constant wiring structure corresponding to a high frequency.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a ceramic multilayer substrate having a low dielectric constant wiring structure corresponding to a high frequency, and a method for manufacturing the ceramic multilayer substrate. .

The ceramic multilayer substrate of the present invention is a ceramic multilayer substrate in which a wiring is formed in each of a plurality of layers made of a sintered body of a green sheet, and a hollow is formed in at least a part of the periphery of the wiring. Wiring was formed.

According to the ceramic multilayer substrate of the present invention, a low dielectric constant aerial wiring can be formed and a multilayer substrate corresponding to a high frequency can be obtained.
In the ceramic multilayer substrate, the aerial wiring may be a hollow internal wiring.

According to this ceramic multilayer substrate, a low dielectric constant aerial internal wiring can be made and a multilayer substrate corresponding to a high frequency can be obtained.
In the ceramic multilayer substrate, the aerial wiring may be a hollow via wiring.

According to this ceramic multilayer substrate, an air via wiring with a low dielectric constant can be formed and a multilayer substrate corresponding to a high frequency can be obtained.
The method for producing a ceramic multilayer substrate according to the present invention includes a drawing step of drawing a liquid pattern on the green sheet by discharging a liquid containing conductive fine particles into droplets by a discharge means and discharging the liquid onto a drawing surface of the green sheet. A drying step of drying the liquid pattern to form a dry pattern made of an aggregate of the conductive fine particles on the green sheet, and laminating the plurality of green sheets on which the dry pattern is formed to form a laminate. A method for producing a ceramic multilayer substrate, comprising: a laminating step, a pressure bonding step of pressurizing the laminated body to form a pressure-bonded body, and a firing step of firing the pressure-bonded body, and before drawing the liquid pattern, A hollow region shape in which a concave portion is formed in a part of a drawing surface of the green sheet on which the dry pattern is formed, and a hollow region is formed by embedding a sublimation material in the concave portion. A metal wiring forming step after the drying step and heating the dry pattern made of the conductive fine particle aggregate to form an internal wiring by metallizing the conductive fine particle aggregate; After the metal wiring forming step, the sublimation material embedded in the concave portion of the hollow region is heated to sublimate the sublimation material so that the metallized internal wiring becomes the air internal wiring. Forming step.

According to the method for producing a ceramic multilayer substrate of the present invention, when a dry pattern composed of an aggregate of conductive fine particles formed on a sublimable material embedded in a recess in a hollow region is heated, the aggregate of conductive fine particles is Before the sublimable material sublimates, it is metalized to form internal wiring. after that,
By heating the sublimable material embedded in the concave portion of the hollow region to sublimate the sublimable material to form a space in the hollow region, the metallized internal wiring becomes an aerial internal wiring.

Therefore, the aerial internal wiring can be easily formed on the ceramic multilayer substrate.
The method for producing a ceramic multilayer substrate according to the present invention includes a drawing step of drawing a liquid pattern on the green sheet by discharging a liquid containing conductive fine particles into droplets by a discharge means and discharging the liquid onto a drawing surface of the green sheet. A drying step of drying the liquid pattern to form a dry pattern made of an aggregate of the conductive fine particles on the green sheet, and laminating the plurality of green sheets on which the dry pattern is formed to form a laminate. A method for producing a ceramic multilayer substrate, comprising: a laminating step, a pressure bonding step of pressurizing the laminated body to form a pressure-bonded body, and a firing step of firing the pressure-bonded body, and before drawing the liquid pattern, A large-diameter via hole having a diameter larger than that of the via hole is formed at a position where the via hole of the green sheet is formed, and a sublimation material is formed in the large-diameter via hole. A hollow region in which a small diameter via hole for the via hole is formed in the large diameter via hole in which the sublimable material is embedded, and a hollow region made of the sublimable material is formed between the small diameter via hole and the large diameter via hole. After the forming step, the filling step of filling the small-diameter via hole with a pattern made of the aggregate of the conductive fine particles, and the drying step, the aggregate of the conductive fine particles filled in the small-diameter via hole Heating the pattern, metallizing the aggregate of conductive fine particles to form via wiring, and heating the sublimation material filled in the hollow region after the metal wiring forming step and the metal wiring forming step Then, an aerial wiring forming step is performed in which the sublimable material is sublimated so that the metalized via wiring becomes an aerial via wiring.

According to the method for manufacturing a ceramic multilayer substrate of the present invention, when a pattern made of an aggregate of conductive fine particles filled in a small-diameter via hole is heated, the aggregate of conductive fine particles is metallized before the sublimable material is sublimated. To form via wiring. Thereafter, the sublimable material embedded in the large-diameter via hole in the hollow region is heated to sublimate the sublimable material to form a space in the hollow region, so that the metalized via wiring becomes an air via wiring.

Therefore, the air via wiring can be easily formed on the ceramic multilayer substrate.
In this method for manufacturing a ceramic multilayer substrate, the firing step may include the metal wiring formation step and the aerial wiring formation step.

According to this method for manufacturing a ceramic multilayer substrate, in the firing step, first, a metalized wiring is formed, and then a sublimable material is sublimated to form a space in a hollow region to form a metallized internal wiring (or via) Wiring) is aerial internal wiring (or air via wiring). Subsequently, finally, the pressure-bonded body is fired to manufacture the ceramic multilayer substrate.

Therefore, since the metal wiring formation process and the air wiring formation process are performed in a series in the firing process, the air internal wiring (or air via wiring) can be efficiently made.
In this method for producing a ceramic multilayer substrate, the sublimable material may be an organic binder of a green sheet composition.

According to the present invention, the organic binder as the sublimable material sublimes before the green sheet is sintered.
In this method for producing a ceramic multilayer substrate, the conductive fine particles may be silver fine particles.

According to the present invention, the aerial internal wiring (or aerial via wiring) made of silver can be formed.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a circuit module comprising a ceramic multilayer substrate manufactured using the manufacturing method of the present invention.

In FIG. 1, a circuit module 10 includes a low temperature co-fired ceramics (LTCC) multilayer substrate 11 as a ceramic multilayer substrate, and a semiconductor chip 12 connected to the LTCC multilayer substrate 11.

The LTCC multilayer substrate 11 has a plurality of LTCC substrates 13. Each LTCC board 13 is
Each is a sintered body of a green sheet and has a thickness of several tens to several hundreds of μm.
Each LTCC substrate 13 is formed with various internal elements 14 such as a resistance element, a capacitive element, and a coil element, and an internal wiring 15 that is electrically connected to each internal element 14. Each LT
A via hole BH is formed in the CC substrate 13, and a via wiring 16 is formed in the via hole BH.

The internal wiring 15 formed on the LTCC multilayer substrate 11 includes an aerial internal wiring 15 a formed in the space SP formed on the LTCC substrate 13. The aerial internal wiring 15a
Unlike the other internal wirings 15, the wiring structure has a low dielectric constant because it is formed in the space SP.

The internal element 14, the internal wiring 15 (aerial internal wiring 15a), and the via wiring 16 are
Each is a sintered body of conductive fine particles, and is formed by an ink jet method using conductive ink.

Next, a method for manufacturing the LTCC multilayer substrate 11 will be described with reference to FIGS. 2 shows L
3 is a flowchart showing a method of manufacturing the TCC multilayer substrate 11, and FIGS.
6 is a process diagram illustrating a method for manufacturing the CC multilayer substrate 11. FIG.

2, in the manufacturing method of the LTCC multilayer substrate 11, a hollow region forming step (step S10) for forming a hollow region for forming the aerial internal wiring 15a in the green sheet that is a precursor of the LTCC substrate 13 is performed. A drawing process (step S11) for drawing a liquid pattern on the formed green sheet and a drying process (step S12) for drying the liquid pattern to form a dry pattern made of an aggregate of conductive fine particles are sequentially executed. Next, LT
In the manufacturing method of the CC multilayer substrate 11, a stacking process (step S13) for stacking a plurality of green sheets to form a stack, and a vacuum packaging process (step S14) for packing the stack under reduced pressure.
Then, a crimping step (step S15) for crimping the laminate to form a crimped body, and a firing step (step S16) for firing the crimped body are sequentially performed.
(Hollow region forming process)
In FIG. 3, the hollow region forming step is a step of forming the hollow region 20 for forming the aerial internal wiring 15 a in the green sheet 18.

In FIG. 3A, the green sheet 18 is a layer made of a glass ceramic composition containing glass ceramic powder, a binder, and the like. The thickness of the green sheet 18 is determined by the internal element 1
4 is formed with several tens of μm in the case of forming a capacitor element, and in other layers 100
It is formed at μm to 200 μm. The green sheet 18 is formed by applying a glass ceramic composition slurryed with a dispersion medium onto a carrier film CF (see FIG. 4) using a sheet forming method such as a doctor blade method or a reverse roll coater method. Can be obtained by drying to a state where it can be handled.

As the dispersion medium, for example, a surfactant, a silane coupling agent, or the like can be used as long as it can uniformly disperse the glass ceramic powder.
The glass ceramic powder is a powder having an average particle diameter of 0.1 μm to 5 μm. For example, a glass composite ceramic obtained by mixing borosilicate glass with ceramic powder such as alumina or forsterite can be used. As the glass ceramic powder, ZnO-M
BaO, a crystallized glass ceramic using gO-Al2O3-SiO2 based crystallized glass
-Al2O3-SiO2 ceramic powder and Al2O3-CaO-SiO2-MgO-B
Non-glass ceramics using 2O3 ceramic powder or the like may be used.

The binder has a function as a binder for the glass ceramic powder, and is a firing step (
It is an organic polymer that can be decomposed and removed easily at about 550 ° C. (air wiring formation step). As the binder, for example, a binder resin such as butyral, acrylic or cellulose can be used. As the acrylic binder resin, for example, a homopolymer of a (meth) acrylate compound such as alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, polyalkylene glycol (meth) acrylate, cycloalkyl (meth) acrylate, or the like is used. Can do. Moreover, as an acrylic binder resin, it can be obtained from a copolymer obtained from two or more of the (meth) acrylate compounds, or from other copolymerizable monomers such as (meth) acrylate compounds and unsaturated carboxylic acids. Can be used.

The binder is, for example, an adipate ester plasticizer, dioctyl phthalate (DO
P), a dibutyl phthalate (DBP) phthalate ester plasticizer, and a plasticizer such as a glycol ester plasticizer may be contained.

As shown in FIG. 3A, the green sheet 18 is penetrated by a circular hole or a conical hole (hereinafter simply referred to as a via hole BH) having a hole diameter of several tens to several hundreds of μm by punching or laser processing. Is formed. The via hole BH is filled with a conductive material 19 such as silver, gold, copper, or palladium in the previous step by a squeegee method using a conductive paste or an inkjet method using a conductive ink.

Next, as shown in FIG. 3B, a recess 21 is formed by laser processing or the like at a position (hollow region 20) where the aerial internal wiring 15a of the green sheet 18 is formed.
As shown in FIG. 3C, the sublimable material 22 is filled.

The sublimable material 22 is an organic polymer that can be easily decomposed and removed in the subsequent baking step (about 550 ° C .: air wiring formation step), similar to the binder of the green sheet 18. As the sublimable material 22, for example, a butyral, acrylic, or cellulose binder resin can be used. Examples of the acrylic binder resin include alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, and polyalkylene glycol (meth).
Homopolymers of (meth) acrylate compounds such as acrylate and cycloalkyl (meth) acrylate can be used. In addition, the acrylic sublimable material resin may be a copolymer obtained from two or more of the (meth) acrylate compounds, or other copolymerizable monomers such as (meth) acrylate compounds and unsaturated carboxylic acids. The copolymer obtained from can be used.

In addition, the sublimable material 22 may contain plasticizers, such as an adipate ester plasticizer, a dioctyl phthalate (DOP), a dibutyl phthalate (DBP) phthalate ester plasticizer, a glycol ester plasticizer, for example.

The via hole BH of each green sheet 18 is filled with the conductive material 19, and the recess 2 is formed at a position (hollow region 20) where the aerial internal wiring 15a of each green sheet 18 is formed.
When 1 is filled with the sublimable material 22, the hollow region forming process is completed, and the drawing process is started.
(Drawing process)
In FIG. 4, a droplet discharge device 31 is used in the drawing process.

The droplet discharge device 31 includes a placement plate 32 for placing the green sheet 18, an ink tank 33 for storing the conductive ink Ik as a liquid, and the conductive ink Ik in the ink tank 33 to the green sheet 18. And a droplet discharge head 34 as discharge means for discharging onto the drawing surface 18a.

The mounting plate 32 is a plate made of a rigid material having substantially the same size as the green sheet 18, and includes positioning pins 32 </ b> P for positioning the green sheet 18 and a heater 32 </ b> H for heating the green sheet 18. Then, when the green sheet 18 is placed on the placement plate 32, the placement plate 32 causes each position on the drawing surface 18 a to drop into the droplet by inserting the positioning pins 32 </ b> P into the positioning holes H formed in the green sheet 18. Positioning with respect to the ejection head 34.

Further, when the green sheet 18 is placed on the placement plate 32, the placement plate 32.
The heater 32H is driven to heat the green sheet 18 to a predetermined drawing temperature.

The conductive ink Ik is a dispersion system of the conductive fine particles Ia in which the conductive fine particles Ia are dispersed in the dispersion medium Ib. The viscosity of the conductive ink Ik is adjusted to 20 cP or less in order to enable discharge of minute droplets D. Yes.

The conductive fine particles Ia are fine particles having a particle diameter of several nm to several tens of nm, such as gold, silver,
Metals such as copper, platinum, palladium, rhodium, osmium, ruthenium, iridium, iron, tin, cobalt, nickel, chromium, titanium, tantalum, tungsten, and indium, or alloys thereof can be used. Since these conductive fine particles having a particle size of several nanometers to several tens of nanometers have a very small particle diameter, the particles are fused and metallized at a very low temperature, for example, hundreds of tens of degrees Celsius.

In the present embodiment, silver fine particles are used as the conductive fine particles Ia. Therefore, silver fine particles having a particle diameter of several nm to several tens of nm are fused and metallized at a few tens of degrees Celsius.
The dispersion medium Ib may be any dispersion medium that uniformly disperses the conductive fine particles Ia. For example, water or an aqueous solution mainly containing water, or an organic solvent mainly containing an organic solvent such as tetradecane can be used. .

The droplet discharge head 34 includes a cavity 35 communicating with the ink tank 33 and the cavity 3.
5 and a pressure generating element 37 connected to the cavity 35. The cavity 35 accommodates the conductive ink Ik from the ink tank 33 and supplies the conductive ink Ik from the ink tank 33 to the nozzle 36.

The nozzle 36 is a nozzle having an opening of several tens of μm. The pressure generating element 37 is a piezoelectric element or a capacitive element that changes the volume of the cavity 35, or a resistance heating element that changes the temperature of the cavity 35, and generates a predetermined pressure inside the cavity 35. When the pressure generating element 37 is driven, the nozzle 36 vibrates the gas-liquid interface (meniscus) of the conductive ink Ik and discharges the conductive ink Ik as a droplet D of several picoliters to several tens of picoliters. .

In the drawing process, the green sheet 18 and the droplet discharge head 34 are relatively moved in the surface direction of the drawing surface 18a, and a plurality of droplets D from the nozzles 36 land on the drawing surface 18a, respectively, on the drawing surface 18a. Unite at As a result, the liquid pattern PL continuous in a predetermined direction forms the drawing surface 1.
It is formed on 8a. The liquid pattern PL is also formed on the sublimable material 22 filled in the recess 21.

Further, since the temperature of the green sheet 18 is heated to a predetermined drawing temperature, the liquid pattern PL is thickened by evaporation of a part of the dispersion medium Ib so that wetting and spreading along the drawing surface 18a is suppressed. It has become.

When the drawing of the liquid pattern PL on the green sheet 18 is completed, the process proceeds to the drying process.
(Drying process)
In FIG. 5, in the drying process, the green sheet 18 on which the liquid pattern PL after the drawing process is formed is carried into a drying device such as a drying furnace and heated to a predetermined drying temperature in a state having the liquid pattern PL. The Since the temperature of the green sheet 18 is heated at a predetermined drying temperature, the liquid pattern PL further promotes the drying. As a result, most of the dispersion medium Ib of the liquid pattern PL is evaporated, and a dry pattern PD composed of an aggregate of the conductive fine particles Ia is formed on the drawing surface 18a.

As described above, when the liquid pattern PL drawn on the green sheet 18 is dried by the drying device to become the dry pattern PD, the process proceeds to the stacking step.
(Lamination process)
In FIG. 6, a base plate 41 for laminating a plurality of green sheets 18 is used in the laminating process. The base plate 41 is a plate material made of a rigid material having substantially the same size as the green sheet 18, and the positioning pins 4 for positioning the plurality of green sheets 18.
1P.

In the stacking process, first, the first green sheet 18 is placed on the base plate 41. By positioning the positioning pin 41P through the positioning hole H, the first green sheet 18 is positioned on the base plate 41.

Next, the second green sheet 18 is placed on the first green sheet 18. The second-layer green sheet 18 is positioned by inserting the positioning pins 41P through the positioning holes H, and only the first-layer green sheet 18 is the first-layer green sheet 1.
8 is laminated.

Thereafter, similarly, a predetermined number of green sheets 18 are sequentially laminated to form a plurality of green sheets 1.
8 is formed (hereinafter simply referred to as the laminate 42).
When a plurality of green sheets 18 are stacked, as shown in FIG. 7, when adjacent green sheets 18 are formed with a recess 21 filled with a sublimable material 22 on one of the green sheets 18, Concave portions 21 filled with a sublimable material 22 formed at opposite positions of the other green sheet 18 are overlapped.
(Decompression packaging process)
In FIG. 8, a cover plate 43 and a vacuum packaging bag 50 are used in the decompression packaging process. The cover plate 43 is a plate material made of a rigid material having substantially the same size as the base plate 41, and a plurality of insertion holes 4 through which the positioning pins 41 </ b> P of the base plate 41 can be inserted.
3h. The vacuum packaging bag 50 is a packaging bag having flexibility that can enclose the base plate 41, the cover plate 43, and the laminated body 42.

In the decompression packaging step, first, the positioning pin 41P is inserted into the insertion hole 43h of the cover plate 43, and the laminate 42 is sandwiched between the base plate 41 and the cover plate 43. The base plate 41 and the cover plate 43 are accommodated in the vacuum packaging bag 50 with the laminated body 42 sandwiched therebetween, and are vacuum-sealed inside the vacuum packaging bag 50 by suction using a sealer or the like. The vacuum-sealed laminate 42 is pressure-bonded by receiving atmospheric pressure via the vacuum packaging bag 50, the base plate 41, and the cover plate 43.
(Crimping process)
In the crimping step, the laminated body 42 after decompression packaging is carried into a hydrostatic pressure pressing device, and the laminated body 42
A pressure-bonded body is formed by applying hydrostatic pressure. While the laminated body 42 is applied with hydrostatic pressure, the dry pattern PD is pressed through the green sheet 18.
(Baking process)
In the firing step, the pressure-bonded body obtained in the pressure-bonding step is taken out from the base plate 41, and the pressure-bonded body is carried into a predetermined firing furnace and fired.

Firing is performed according to the following procedure.
The drying pattern P drawn on each green sheet 18 with the temperature in the firing furnace set to a few tens of degrees Celsius
The conductive fine particles Ia of D are fused together, and the dry pattern PD made of the aggregate of the conductive fine particles Ia is metalized to form a wiring (metal wiring forming step). At this time, the recess 21
As shown in FIG. 9A, the dry pattern PD made of the aggregate of conductive fine particles Ia formed on the sublimable material 22 filled in the metal is also metalized to form the internal wiring 1.
5

After the dry pattern PD is made into a hard and non-bent metalized internal wiring 15, the temperature in the firing furnace is gradually raised from 300 ° C to 300 ° C to 600 ° C. The temperature is 300
In the process of increasing from 600C to 600C, the binder contained in the green sheet 18 sublimates (hollow wiring forming process).

At this time, the sublimable material 22 filled in the concave portion 21 also sublimates and disappears as a gas.
When the sublimable material 22 sublimates and disappears, the space S is formed in the concave portion 21 filled with the sublimable material 22.
P is formed. Then, the metalized internal wiring 15 formed on the sublimable material 22 filled in the recess 21 is arranged in a state of floating in the space SP. That is, the metallized internal wiring 15 arranged in a floating state in the space SP becomes an aerial internal wiring 15a as shown in FIG. 9B.

When the binder contained in the green sheet 18 is sublimated, the temperature in the firing furnace is raised to, for example, 800 ° C. to 9000 ° C., and the green sheet 18 is fired. The firing temperature is appropriately changed according to the composition of the green sheet 18, but is a temperature at which the metallized internal wiring 15 (aerial internal wiring 15a) does not lose its shape in the space SP.

When the firing is completed and the pressure-bonded body is taken out from the firing furnace and cooled, the LTCC multilayer substrate 11
Is formed.
In addition, when using silver, gold | metal | money, platinum, palladium etc. as dry pattern PD, you may bake in air | atmosphere. In the firing step, the pressure-bonded body may be fired while being pressed at a pressure smaller than the hydrostatic pressure in the pressure-bonding step. According to this, the flatness of the LTCC multilayer substrate 11 is improved,
Warpage and peeling of the green sheet 18 can be prevented.

Next, effects of the embodiment configured as described above will be described below.
(1) According to the above embodiment, the aerial internal wiring 15 a is formed on the LTCC multilayer substrate 11. Accordingly, the aerial internal wiring 15 a has a low dielectric constant wiring structure unlike the other internal wiring 15. As a result, the LTCC multilayer substrate 11 becomes a multilayer substrate corresponding to a high frequency and can be used for the circuit module 10 corresponding to a high frequency.

(2) According to the present embodiment, the temperature at which the sublimable material 22 sublimates the dry pattern PD made of the aggregate of the conductive fine particles Ia formed on the sublimable material 22 embedded in the concave portion 21 of the hollow region 20. By heating at a lower temperature, the aggregate of the conductive fine particles Ia was metalized into the internal wiring 15 before the sublimable material 22 sublimated. Thereafter, the sublimable material 22 embedded in the recess 21 of the hollow region 20 is heated at a temperature lower than the sintering temperature of the green sheet 18 to sublimate the sublimable material 22 to make the hollow region 20 a space SP. Metalized internal wiring 15
Is the aerial internal wiring 15a.

Finally, the green sheet 18 has a temperature at which the aerial internal wiring 15a does not lose its shape.
The multilayer substrate 11 was manufactured by heating to a temperature for sintering the substrate.
Therefore, the aerial internal wiring 15a can be easily formed by a series of manufacturing steps of the multilayer substrate 11 except that the hollow region 20 is formed in the green sheet 18 in the previous step.

(3) According to this embodiment, since the metal wiring formation process and the aerial wiring formation process are performed in a series in the firing process, the aerial internal wiring 15a can be made efficiently.
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the present embodiment is different from the first embodiment in that some of the many via wirings 16 formed in the LTCC multilayer substrate 11 are formed as air via wirings 16a. Therefore, only the different parts will be described for convenience of explanation.

Note that the green sheet 18 is formed by several tens of μm to several hundreds of μm by punching or laser processing.
A via hole BH having a hole diameter of m is formed through. The via hole BH is filled with a conductive material made of silver, which will be the via wiring 16 in a later process, by a squeegee method using a conductive paste, an ink jet method using a conductive ink, or the like.

Further, as shown in FIG. 10A, a position (hollow region 20) where the aerial via wiring 16a of the green sheet 18 is formed has a large diameter via hole BH1 larger in diameter than the via hole BH by punching or laser processing. Is formed. Then, as shown in FIG. 10B, the large diameter via hole BH1 is filled with a sublimable material 22 (filling step).

When the large diameter via hole BH1 is filled with the sublimable material 22, the large diameter via hole BH1 filled with the sublimable material 22 has a smaller diameter via hole smaller than the large diameter via hole BH1, as shown in FIG. BH2 is opened by punching or laser processing.

When the small-diameter via hole BH2 is formed, the hollow via pattern BP made of conductive fine particles made of silver that will become the air via wiring 16a in the subsequent process is formed by the inkjet method using the small-diameter via hole BH2 and the conductive ink Ik. As shown in (d), it is filled (drawn). Subsequently, as shown in FIG. 10 (e), a liquid pattern PL for the internal wiring 15 is formed on the drawing surface 18 a of each green sheet 18.

Then, after a drying process, a plurality of green sheets 18 are laminated as shown in FIG. That is, the hollow via pattern BP is laminated so as to be connected to the dry pattern PD formed on the upper green sheet 18 and the dry pattern PD formed on the lower green sheet 18.

Then, after passing through the decompression packaging process and the crimping process, in the firing process, as shown in FIG. 11B, the hollow via pattern BP made of conductive fine particles of the small diameter via hole BH2 becomes the metalized via wiring 16. Eventually, the sublimable material 2 filled around the metalized wiring
2 sublimates and disappears as a gas to form a space SP. Then, the metalized via wiring 16 disposed in the space SP becomes an aerial via wiring 16a as shown in FIG.

Also in this embodiment, the via wiring 16 can be an air via wiring 16a having a low dielectric constant. Therefore, the ceramic multilayer substrate 11 having the aerial via wiring 16a becomes a ceramic multilayer substrate corresponding to a high frequency.

Next, effects of the embodiment configured as described above will be described below.
(1) According to the embodiment, the air via wiring 16 a is formed on the multilayer substrate 11. Therefore, unlike the other via wiring 16, the air via wiring 16a has a low dielectric constant wiring structure.
As a result, the LTCC multilayer substrate 11 becomes a multilayer substrate corresponding to a high frequency and can be used for the circuit module 10 corresponding to a high frequency.

(2) According to this embodiment, the conductive fine particles are heated at a temperature lower than the temperature at which the sublimable material 22 is sublimated by heating the hollow via pattern BP made of the aggregate of the conductive fine particles Ia filled in the small-diameter via hole BH2. Before the sublimable material 22 sublimated, the Ia aggregate was metalized to form via wiring 16.

Thereafter, the sublimation material 22 embedded in the large-diameter via hole BH1 is heated at a temperature lower than the sintering temperature of the green sheet 18 to sublimate the sublimation material 22 to make the hollow region 20 a space SP. The completed via wiring 16 becomes an air via wiring 16a.

Finally, the temperature of the air via wiring 16a does not change its shape, and the green sheet 18
The multilayer substrate 11 was manufactured by heating to a temperature for sintering the substrate.
Therefore, as in the first embodiment, the air via wiring 16a can be easily made by a series of manufacturing steps of the multilayer substrate 11 except that the hollow region 20 is formed in the green sheet 18 in the previous step.

(3) According to the present embodiment, as in the first embodiment, since the metal wiring formation process and the air wiring formation process are performed in a series in the firing process, the air via wiring 16a is efficiently formed. be able to.

In addition, you may change the said embodiment as follows.
In the first embodiment, the aerial internal wiring 15a is embodied in the multilayer substrate 11 having the aerial via wiring 16a in the second embodiment. However, in the multilayer substrate 11 including the aerial internal wiring 15a and the aerial via wiring 16a, You may apply.

-In 1st Embodiment, it was set as the recessed part 21 which has a bottom part as a recessed part of the hollow area | region 20, but FIG.
As shown in FIG. 2, a through hole 21 a having a shape penetrating the green sheet 18 may be used as the concave portion of the hollow region 20.

That is, as shown in FIG. 12A, the green sheet 18 is filled with the conductive material 19 such as silver, gold, copper, palladium in the via hole BH formed by punching or laser processing in the previous process. On the other hand, as shown in FIG. 12B, a through hole 21a as a concave portion is formed by penetrating at a position (hollow region 20) where the aerial internal wiring 15a of the green sheet 18 is formed by punching or laser processing. . And with respect to the through hole 21a, FIG.
The sublimable material 22 is applied as shown in FIG.

Thereafter, similar aerial internal wiring 15a can be formed by obtaining the same process as in the first embodiment.
-In 1st Embodiment, when the some green sheet 18 is laminated | stacked, as shown in FIG. 7, it is the adjacent green sheet 18, Comprising: The recessed part 21 by which the sublimation material 22 was filled into one green sheet 18 , The concave portions 21 filled with the sublimable material 22 formed at the opposite positions of the other green sheet 18 were overlapped. Any one of these may be omitted. In this case, the aerial internal wiring 15a in which the space SP is formed on the upper side or the lower side is formed.

In the above embodiment, in the laminating step, the green sheet 18 may be heated to soften the hardness of the green sheet 18.
As a result, the load on the drying pattern PD due to atmospheric pressure is reduced and deformation and the like are suppressed by the amount that the green sheet 18 is softened during decompression packaging. As a result, the processing accuracy of the pattern formed on the LTCC substrate 13 can be improved.

-According to the said embodiment, in the crimping | compression-bonding process, the green sheet 18 may be heated and the green sheet 18 may be softened.
Thus, the dry pattern PD by hydrostatic pressure is as much as the green sheet 18 is softened.
This reduces the load applied and reduces deformation and the like. As a result, the processing accuracy of the pattern formed on the LTCC substrate 13 can be improved.

In the above embodiment, the green sheet 18 is heated to the drawing temperature in the drawing step, but this may be omitted.
In the above embodiment, the laminate 42 sandwiched between the base plate 41 and the cover plate 43 is packaged under reduced pressure. For example, the laminate 42 placed on the base plate 41, that is, the laminate 42 may be packaged under reduced pressure without using the cover plate 43, or only the laminate 42 may be packaged under reduced pressure. Also good.

In the above embodiment, the droplet discharge means is embodied in the piezoelectric element drive type droplet discharge head 34. However, the present invention is not limited to this, and the droplet discharge head may be embodied as a resistance heating type or electrostatic drive type discharge head.

Sectional drawing which shows a circuit module. The flowchart which shows the manufacturing method of a ceramic multilayer substrate. It is a figure explaining the hollow region formation process of the manufacturing method of a ceramic multilayer substrate, (a) is a sectional view of a green sheet before forming a hollow region, (b) is a sectional view of a green sheet showing a concave portion of the hollow region, (C) is sectional drawing which shows the state which filled the sublimation material in the recessed part. The figure which shows the drawing process of the manufacturing method of a ceramic multilayer substrate. The figure which shows the drying process of the manufacturing method of a ceramic multilayer substrate. The figure which shows the lamination process of the manufacturing method of a ceramic multilayer substrate. Sectional drawing which shows the lamination | stacking state of the green sheet in the sublimation material part with which the recessed part was filled. The figure which shows the pressure reduction packaging process of the manufacturing method of a ceramic multilayer substrate. (A) is sectional drawing which shows the metallized wiring in a baking process, (b) is sectional drawing which shows aerial wiring in a baking process. It is a figure explaining 2nd Embodiment, Comprising: (a) is sectional drawing of the green sheet which shows the large diameter via hole formed in the hollow area, (b) is the green which shows the state which filled the sublimation material into the large diameter via hole. Sectional view of sheet, (c) is a sectional view of a green sheet showing a small diameter via hole, (d) is a sectional view of a green sheet showing a hollow via pattern formed in the small diameter via hole, (e) is a drawing on the drawing surface of the green sheet Sectional drawing of the green sheet which shows the done liquid pattern. It is a figure explaining 2nd Embodiment, (a) is sectional drawing which shows the lamination | stacking state of the green sheet in the sublimation material part with which the via hole was filled, (b) is sectional drawing which shows the metallized wiring, (c) ) Is a cross-sectional view showing aerial wiring. It is a figure explaining another example of the manufacturing method of a ceramic multilayer substrate, (a) is sectional drawing of the green sheet before hollow area formation, (b) is sectional drawing of the green sheet which shows the recessed part of a hollow area, (c) ) Is a cross-sectional view showing a state in which a concave portion is filled with a sublimable material.

Explanation of symbols

BH ... via hole, BH1 ... large diameter via hole, BH2 ... small diameter via hole, BP ... hollow via pattern, D ... droplet, Ia ... conductive fine particle, Ik ... conductive ink, PL ... liquid pattern, PD ... dry pattern, 11 ... Ceramic multilayer substrate, 15 ... internal wiring, 15a ... air internal wiring, 16 ... via wiring, 16a ... air via wiring, 18 ... green sheet, 18a ... drawing surface, 20 ... hollow region, 21 ... concave, 21a ... through hole, 22 ... sublimation material, 31 ... droplet discharge device, 34 ... droplet discharge head, 42 ... laminate, 50 ... vacuum packaging bag.

Claims (5)

A drawing step of drawing a liquid pattern on the green sheet by discharging a liquid containing conductive fine particles into droplets by a discharge means and discharging the liquid onto a drawing surface of the green sheet;
A drying step of drying the liquid pattern to form a dry pattern comprising an aggregate of the conductive fine particles on the green sheet;
A stacking step of stacking a plurality of the green sheets on which the dry pattern is formed to form a stack;
A pressure bonding step of pressurizing the laminate to form a pressure bonded body;
A method for producing a ceramic multilayer substrate having a firing step of firing the pressure-bonded body,
Before drawing the liquid pattern, a hollow region forming step of forming a hollow region by forming a recess in a part of the drawing surface of the green sheet on which the dry pattern is formed, and embedding a sublimable material in the recess When,
After the drying step, heating a dry pattern made of the aggregate of conductive fine particles, metalizing the aggregate of conductive fine particles to form an internal wiring; and
After the metal wiring forming step, the sublimation material embedded in the concave portion of the hollow region is heated to sublimate the sublimation material so that the metallized internal wiring becomes the air internal wiring. A method for producing a ceramic multilayer substrate, comprising: a forming step. A drawing step of drawing a liquid pattern on the green sheet by discharging a liquid containing conductive fine particles into droplets by a discharge means and discharging the liquid onto a drawing surface of the green sheet;
A drying step of drying the liquid pattern to form a dry pattern comprising an aggregate of the conductive fine particles on the green sheet;
A stacking step of stacking a plurality of the green sheets on which the dry pattern is formed to form a stack;
A pressure bonding step of pressurizing the laminate to form a pressure bonded body;
A method for producing a ceramic multilayer substrate having a firing step of firing the pressure-bonded body,
Before drawing the liquid pattern, a large-diameter via hole larger than the via hole is formed at a position where the via hole is formed in the green sheet, and a sublimation material is embedded in the large-diameter via hole, and then the sublimation is performed. Forming a small-diameter via hole for the via hole in a large-diameter via hole embedded with a conductive material, and forming a hollow region made of the sublimable material between the small-diameter via hole and the large-diameter via hole; and
A filling step of filling the small-diameter via hole with a pattern made of an aggregate of the conductive fine particles;
After the drying step, from an aggregate of conductive fine particles filled in the small diameter via hole
A metal wiring forming step of heating the pattern to metallize the aggregate of conductive fine particles to form a via wiring;
After the metal wiring formation step, the sublimation material filled in the hollow region is heated to sublimate the sublimation material so that the metallized via wiring becomes an air via wiring. And a method for producing a ceramic multilayer substrate. In the manufacturing method of the ceramic multilayer substrate according to claim 1 or 2 ,
The method for producing a ceramic multilayer substrate, wherein the firing step includes the metal wiring formation step and the air wiring formation step. In the manufacturing method of the ceramic multilayer substrate of any one of Claims 1-3 ,
The method for producing a ceramic multilayer substrate, wherein the sublimable material is an organic binder of the composition of the green sheet. In the manufacturing method of the ceramic multilayer substrate according to any one of claims 1 to 4 ,
The method for producing a ceramic multilayer substrate, wherein the conductive fine particles are silver fine particles.

Images