JP2005064350A - Method for manufacturing multilayer ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a multilayer ceramic substrate which has an excellent dimensional accuracy and has a high bond strength and a high plating performance for a wiring layer as a surface electrode formed on a front or back surface. <P>SOLUTION: The method for manufacturing a multilayer ceramic substrate includes steps of: laminating a plurality of green sheets s1 to s3 having wiring layers 4, 6, 8, 10 formed on its front or back surface and sinter shrinkage suppressing sheets y1, y2 located on a front surface 1 and a back surface 2 of the uppermost and lowermost green sheets s1, s3 and having a sintering temperature higher than that of the green sheets s1 to s3 to form a composite laminate; sintering the composite laminate at the sintering temperature of the green sheets s1 to s3; removing unsintered sinter-shrinkage suppressing sheets y1, y2 in the composite laminate after sintered; and heating the wiring layers 4, 10 arranged on the front and back surfaces 1, 2 of the uppermost and lowermost ceramic layers S1, S3 at a temperature lower than the sintering temperature of the green sheets s1 to s3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a multilayer ceramic substrate having excellent dimensional accuracy and having high adhesion strength and plating properties of a wiring layer (surface layer electrode) formed on a front surface or a back surface.

Baking at the firing temperature of the green sheet in a state where a plurality of green sheets formed with conductive paste of a predetermined pattern are laminated on the front and back surfaces, and shrinkage suppression sheets having a firing temperature higher than that of the green sheets on both sides are laminated. Then, a manufacturing method for obtaining a multilayer ceramic substrate with high dimensional accuracy in the planar direction by removing the unfired shrinkage suppression sheet has been proposed.
For example, in order to remove the shrinkage suppression sheet, a method of spraying ceramic powder or water and ceramic powder has been proposed (see, for example, Patent Document 1).
In addition, a method has also been proposed in which an aqueous solution in which alumina abrasive grains are dispersed is sprayed onto the shrinkage suppression sheet via compressed air (see, for example, Patent Document 2).

WO99 / 55610 (Pages 1 to 12, FIG. 1) JP 2000-277914 A (pages 1-7, FIG. 1)

  However, when the shrinkage-suppressing sheet is removed by spraying water containing ceramic powder together with air as in the above two methods, the surface of the multilayer electrode substrate exposed on the trace and the surface of the surface electrode located on the back surface are also sprayed. Will be damaged. The surface layer electrode having such a damage lowers the adhesion strength with the ceramic substrate and also reduces the plating property.Therefore, solder wettability and solder erosion property (metal in the solder) There has been a problem that connection reliability is lacking due to deterioration of the property of excessively absorbing elements.

  The present invention solves the problems in the background art described above, and provides a method for producing a multilayer ceramic substrate having excellent dimensional accuracy and high adhesion strength and plating properties of the wiring layer of the surface layer electrode formed on the front and back surfaces. The issue is to provide.

In order to solve the above-mentioned problems, the present invention provides a wiring layer which is a surface layer electrode which is sintered on both sides and has a damaged surface after removing unfired firing shrinkage-suppressing green sheets located on both sides of the fired multilayer ceramic substrate. Was conceived of heating to a temperature lower than the firing temperature and re-sintering.
That is, the method for manufacturing a multilayer ceramic substrate of the present invention (Claim 1) includes a plurality of green sheets in which a wiring layer is formed on at least one of the front surface and the back surface, and the uppermost and lowermost green sheets among these green sheets. A lamination step of laminating a firing shrinkage suppression sheet disposed on the front and back surfaces of the sheet and having a firing temperature higher than the firing temperature of the green sheet, and forming the composite laminate; At least one of the front and back surfaces of the uppermost layer and the lowermost ceramic layer, and a removal step of removing the unfired firing shrinkage suppression sheet in the composite laminate after firing, Heating the wiring layer disposed on the substrate at a temperature lower than the firing temperature of the green sheet. To.

  The wiring layer is a sintered body of metal powder sintered in the firing step, and is located on the front and back surfaces of the multilayer ceramic substrate, and is connected to electronic components to be mounted on the front surface and a printed circuit board on the back surface side. It is a surface layer electrode utilized for. The wiring layer is made of a conductor such as Cu, Ag, W, Mo, Au, Pt, Pd, or an alloy thereof. Furthermore, it is also possible to obtain a multilayer ceramic substrate with a cavity by previously forming a through-hole in the uppermost layer and the green sheet close thereto in advance.

  Further, in the present invention, the green sheet is mainly composed of glass and alumina, and the firing shrinkage suppression sheet contains at least alumina and the glass content is less than the green sheet or does not contain glass. A method for manufacturing a multilayer ceramic substrate (Claim 2) is also included. In addition, when a baking shrinkage suppression sheet contains glass, the content is 50 wt% or less less than that of a green sheet.

Furthermore, the present invention may include a method for producing a multilayer ceramic substrate, wherein the removing step is performed by spraying water, hard particles, or a mixture thereof onto the unfired fired shrinkage suppression sheet.
In addition, the present invention may include a method for producing a multilayer ceramic substrate, wherein the green sheet firing temperature is 800 to 1000 ° C., and the heating temperature in the heating step is 600 to 900 ° C. .

  According to the method for manufacturing a multilayer ceramic substrate (Claim 1), the wiring layer (surface electrode) made of sintered metal powder has a surface that is damaged when the firing shrinkage suppression sheet is removed. However, a relatively flat surface can be obtained by subsequent heating and re-sintering. Therefore, the adhesive strength between the adjacent ceramic layers can be recovered, Ni plating and Au plating can be easily applied, and the wettability and solder erosion property with the solder used for connection with electronic parts and the like are improved. Connection reliability can be improved.

  Moreover, according to the said manufacturing method (Claim 2), in the said baking process, since the glass component in the said green sheet osmose | permeates into the said adjacent baking shrinkage suppression sheet, it followed the planar direction of the green sheet in each layer. A ceramic layer with high dimensional accuracy can be obtained by reliably suppressing firing shrinkage. Therefore, it is possible to reliably provide a multilayer ceramic substrate having excellent connection accuracy and dimensional accuracy.

In addition, in the said removal process, when it is decided to spray water, a hard particle, or a mixture thereof with respect to the unbaking said baking shrinkage suppression sheet, the said baking shrinkage suppression sheet is removed reliably. Is possible.
Moreover, when the firing temperature of the green sheet is 800 to 1000 ° C. and the heating temperature in the heating step is 600 to 900 ° C., the green sheet containing glass can be fired at a relatively low temperature. At the same time, the wiring layer made of a sintered body of a metal such as Cu or Ag or an alloy thereof can be formed. Moreover, by heating such wiring layers in the above temperature range, it is ensured that they are re-sintered to form a wiring layer having a relatively flat and dense surface.

In the following, the best mode for carrying out the present invention will be described.
FIG. 1 shows a cross section of green sheets s1 to s3 for obtaining a multilayer ceramic substrate manufactured according to the present invention. The green sheets s1 to s3 are mainly composed of alumina and glass at a weight ratio of about 1: 1, and a ceramic slurry obtained by adding a necessary amount of an organic binder and a plasticizer to these is about 0 by a doctor blade method. It is formed into a sheet having a thickness of 2 mm.
As shown in FIG. 1, in the green sheets s <b> 1 to s <b> 3, a plurality of conductive paste cylinders v to be via conductors v penetrates between the front and back surfaces. Moreover, the conductive paste 4-10 of the predetermined pattern used as the wiring layers 4-10 later is formed in the printing method etc. at least one of the surface of the green sheets s1-s3. In addition, the said electrically conductive paste contains Ag powder, for example.

Next, as shown in FIG. 2, the green sheets s <b> 1 to s <b> 3 are stacked and pressed to form a stacked body ss. At this time, the conductive pastes 4 to 10 having a predetermined pattern to be the wiring layers 4 to 10 are connected via the columnar body v of the conductive paste to be the via conductors v later. The conductive pastes 4 and 10 positioned on the front surface 1 and the back surface 2 of the laminated body ss become wiring layers 4 and 10 that are surface layer electrodes later.
Next, as shown in FIG. 3, firing shrinkage suppression sheets y1 and y2 are laminated and pressure-bonded on the front surface 1 and the back surface 2 of the laminate ss to form a composite laminate (lamination step). The firing shrinkage suppression sheets y1 and y2 contain alumina and do not contain glass, or the glass content is 50 wt% or less lower than the green sheets s1 to s3, and higher than the green sheets s1 to s3. is there. The fired shrinkage suppression sheets y1 and y2 are formed into a sheet having a thickness of about 0.3 mm by the same method as described above.

Further, in the state shown in FIG. 3, the composite laminate is put in a firing furnace (not shown) and fired at the firing temperature (about 900 ° C.) of the green sheets s1 to s3 (firing step).
As a result, the green sheets s1 to s3 are fired to become ceramic layers S1 to S3. At the same time, the conductive pastes 4 to 10 and the cylindrical body v are sintered to become the wiring layers 4 to 10 and the via conductors v.
The firing shrinkage suppression sheets y1 and y2 are removed by spraying a mixture of water and hard particles such as alumina on the unfired firing shrinkage suppression sheets y1 and y2 in the composite laminate after firing (removal step). ). In addition, you may perform this removal process by the method of injecting water or a hard particle with respect to baking shrinkage suppression sheet y1, y2. As a result, as shown in FIG. 4, a multilayer ceramic substrate SS including the ceramic layers S1 to S3 is obtained.

At this time, as shown in FIG. 5 in which the one-dot chain line portion X in FIG. 4 is enlarged, the wiring layer 4 (10) of the surface electrode located on the front surface 1 and the back surface 3 of the multilayer ceramic substrate SS is fired in the removing step. When the shrinkage-suppressing sheets y1 and y2 are removed, the surface 4a (10a) has an uneven shape due to the collision with the hard particles, and a deep depression k is included in part. The wiring layer 4 (10) having such a surface 4a (10a) has low adhesion strength with the ceramic layers S1 and S3, and may be insufficient in terms of plating properties and solder wettability.
Therefore, the multilayer ceramic substrate SS is placed in a firing furnace (not shown) and heated at a temperature (about 800 ° C.) lower than the firing temperature of the green sheets s1 to s3 for about 30 minutes (heating step). Note that the inside of the firing furnace is an inert gas atmosphere in advance.

As a result, as shown in FIG. 6, the wiring layer 4 (10) is re-sintered to become a wiring layer 4 (10) having a comparatively gentle surface 4 b (10 b), and the adhesion strength with the ceramic layers S 1 and S 3 is improved. improves. Further, the surface 4b (10b) can be satisfactorily subjected to ultra-thin Ni plating and Au plating, and the formed Ni plating film and Au plating film become a more gentle surface.
For this reason, wettability with a low melting point alloy such as solder used when connecting to an electronic component such as an IC chip mounted on the surface 1 of the multilayer ceramic substrate SS is improved, and solder erosion is surely suppressed. Can do.

Further, the wiring layer (surface layer electrode) 10 located on the back surface 2 of the multilayer ceramic substrate SS used when the multilayer ceramic substrate SS is mounted on a printed board such as a mother board (not shown) is also extremely thin on the gentle surface 10b. Ni plating and Au plating can be applied satisfactorily. In addition, since the Ni plating film and Au plating film to be coated have a smoother surface, it is possible to increase the wettability of solder used between connection terminals such as a mother board and to reduce the solder erosion property. It becomes. A solder ball or a conductor pin may be fixed to the Ni plating film and Au plating film of the wiring layer 10 by soldering.
Therefore, according to the manufacturing method of the present invention as described above, it is possible to reliably provide the multilayer ceramic substrate SS with high connection reliability.

FIG. 7 shows a cross section of a laminate ss3 of an applied form in which a laminate ss2 including the same green sheets s4 and s5 having through holes C on the inside is laminated on the surface 1 of the same laminate ss1 as the laminate ss. Indicates.
As shown in FIG. 7, conductive pastes 12 and 14 having a predetermined pattern, which will later become wiring layers 12 and 14, are formed between the green sheets s4 and s5 and on the surface 11 of the laminate ss2 by a printing method or the like. In addition, the conductive pastes 12 and 14 are connected via a cylindrical column v of a conductive paste that will be a via conductor v later. Further, a conductive paste 5 for solder bumps 5 containing, for example, Ag powder is provided on the conductive paste 4 located on the surface 1 side of the multilayer body ss1 and exposed at the bottom surface of the through hole C.

Next, as shown in FIG. 8, a composite laminate is formed by laminating and pressing the same firing shrinkage suppression sheets y1 and y2 on the front surface 11 and the back surface 2 of the laminate ss3 (lamination step). . At this time, for example, ceramic particles may be filled in the through holes C of the multilayer body ss2.
Next, the composite laminate is put into a firing furnace (not shown) and fired at the firing temperature (about 900 ° C.) of the green sheets s1 to s5 (firing step).
As a result, the green sheets s1 to s5 are fired to become ceramic layers S1 to S5. At the same time, the conductive pastes 4 to 14 and the cylindrical body v are sintered to become the wiring layers 4 to 14 and the via conductors v.

In the same manner as above, a mixture of water and hard particles such as alumina is sprayed on the unfired firing shrinkage suppression sheets y1 and y2 in the composite laminate after firing to remove the firing shrinkage suppression sheets y1 and y2 ( Removal step).
As a result, a multilayer ceramic substrate with a cavity C having ceramic layers S1 to S5, wiring layers 4 to 14 including wiring layers 10 and 12 for surface layer electrodes, via conductors v, and solder bumps 5 is formed. At this time, the ceramic particles filled in the through hole C are also removed.
And in order to smooth the uneven surface 12a (10a) of the wiring layer 12 (10) which is a surface layer electrode, as shown in the left side of FIG. 9 which expanded after the removal process, the dashed-dotted line part Z in FIG. The multilayer ceramic substrate with the cavity C is put in a firing furnace (not shown) and heated at a temperature (about 800 ° C.) lower than the firing temperature of the green sheets s1 to s5 for about 30 minutes (heating step).

As a result, as shown on the right side of FIG. 9, the wiring layer 12 (10) which is a surface layer electrode is re-sintered to become a wiring layer 12 (10) having a relatively gentle surface 12b (10b), and the ceramic layer S4 ( The adhesion strength with S3) is improved. Further, the surface 12b (10b) can be satisfactorily subjected to ultra-thin Ni plating and Au plating, and the Ni plating film and Au plating film to be coated become a more gentle surface.
Therefore, the multilayer ceramic substrate with the cavity C can also be reliably mounted on the front surface 11 via the wiring layer 12 and the solder, and can be reliably mounted on the motherboard or the like via the wiring layer 10 on the back surface 2. be able to. Furthermore, another electronic component can be mounted in the cavity C via the solder bump 5.
Therefore, according to the manufacturing method of the present invention as described above, it is possible to reliably provide a multilayer ceramic substrate with a cavity C with high connection reliability.

The present invention is not limited to the embodiments described above.
For example, the wiring layer 4 and the via conductor v may be a metal such as W, Mo, or Cu, or an alloy such as Ag—Cu, Cu—W, Ag—Pd, or Ag—Pt. In the preparation step, a conductive paste containing these metal powders or alloy powders may be used.
Further, a solder ball or a conductor pin may be soldered to the Ni-plated and Au-plated surface 10b of the wiring layer 10 of the surface electrode located on the back surface 2 such as the multilayer ceramic substrate SS.
Furthermore, a plurality of cavities C may be formed in the multilayer ceramic substrate with cavities C. In this case, a plurality of through holes c may be opened in the green sheets s4 and s5 in advance.

Sectional drawing which shows the some green sheet used for the manufacturing method of this invention. Sectional drawing which shows the laminated body which laminated | stacked the said some green sheet. Sectional drawing which shows the lamination process which forms the composite laminated body containing the said laminated body. Sectional drawing which shows the laminated body after the removal process of the said manufacturing method. The expanded sectional view of the dashed-dotted line part X in FIG. The expanded sectional view similar to FIG. 5 which shows the heating process of this invention. Sectional drawing which shows the laminated body of an applied form. Sectional drawing which shows the lamination process which forms the composite laminated body containing the said laminated body. FIG. 9 is an enlarged cross-sectional view showing an alternate long and short dash line portion Z in FIG. 8 and a heating step.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ........ Front side 2 ........... Back side 4,6-14 ... Wiring layer s1-s5 ... Green sheet y1, y2 ... Sintering suppression sheet S1-S5 ... Ceramic layer SS ..... ...... Multilayer ceramic substrate

Claims (2)

A plurality of green sheets in which a wiring layer is formed on at least one of the front surface and the back surface, and the green sheets disposed on the front and back surfaces of the uppermost and lowermost green sheets among these green sheets and higher than the firing temperature of the green sheet A lamination step of laminating a firing shrinkage suppression sheet having a firing temperature to form a composite laminate;
A firing step of firing the composite laminate at the firing temperature of the green sheet;
A removal step of removing the unfired firing shrinkage suppression sheet in the composite laminate after firing,
A heating step of heating the wiring layer disposed on at least one of the front and back surfaces of the uppermost layer and the lowermost ceramic layer at a temperature lower than the firing temperature of the green sheet,
A method for producing a multilayer ceramic substrate. The green sheet is mainly composed of glass and alumina, and the firing shrinkage suppression sheet contains at least alumina and the glass content is less than the green sheet or does not contain glass.
The manufacturing method of the multilayer ceramic substrate of Claim 1.

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