JPH08335780A - Production of multilayer ceramic wiring board - Google Patents

Abstract

PURPOSE: To enhance the migration resistance while satisfying the requirements of conduction resistance, metallization strength and solder wettability by coating a ceramic green sheet with a plurality of kinds of photosensitive paste composed of conductor composition powder such that the coatings are overlapped in the range for forming each wiring and then exposing the photosensitive paste. CONSTITUTION: A ceramic green sheet is coated uniformly with two kinds or more of photosensitive paste composed, respectively, of conductor compositions while filling the range for forming each conductor wiring such that coatings of respective photosensitive paste are overlapped. The conductor wiring part of photosensitive paste coating is then irradiated selectively with ultraviolet rays through a shade mask and the unirradiated part is dissolved using a specified developer and removed. Subsequently, a first layer green sheet 4 and a third layer green sheet 5 are thermocompressed to the upper and lower sides of the green sheet 3 on which conductor patterns 1, 2 are formed. Finally, it is fired and brazed with I/O pins 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic wiring board used as an electronic circuit component.

[0002]

2. Description of the Related Art In recent years, conductor wiring on a ceramic green sheet forming a multilayer ceramic wiring substrate has become fine and fine conductor wiring with a narrow pitch as IC packages, multilayer wiring substrates, etc. have become higher in function, higher in density and smaller in size. Is needed. On the other hand, the required characteristics such as conduction resistance, metallization strength and solder wettability of the conductor wiring are becoming more severe.

As a method for forming a fine conductor wiring with a narrow pitch, a conductor wiring forming method applying a photolithography method in place of the usual thick film printing method has been proposed. For example, a photosensitive paste is applied to the entire surface of a ceramic green sheet, and the conductor wiring portion is selectively irradiated with ultraviolet rays, followed by development using a predetermined developing solution to obtain a conductor wiring on the green sheet.

Further, as a method for satisfying the required characteristics such as conduction resistance, metallization strength, and solder wettability of the conductor wiring, two or more kinds of conductors having partially different compositions for the conductor wiring formed on the ceramic green sheet are used. The wiring is formed and the conductor wiring in each part is devised so as to meet the required characteristics. As an example of this, in a multilayer ceramic wiring board that can be fired at a low temperature of 800 to 1000 ° C., an inexpensive conductor containing Ag as a main component is arranged in the inner layer of the ceramic substrate, and Ag-Pd as the main component is used as the surface layer to conduct electricity. There is a low-temperature fired ceramic substrate in which a conductor having a resistance lower than that of an Ag conductor and excellent in migration resistance is arranged. The surface layer ceramic green sheet before lamination constituting this is composed of Ag conductor and A
It has a conductor wiring structure in which g-Pd conductors are connected. As another example, in an alumina-based high temperature fired substrate, a conductor mainly composed of W or Mo is arranged in the inner layer of the ceramic substrate, and metallization strength such as wire bonding property and solderability of the surface layer is required. In the portion to be formed, there is a multilayer ceramic substrate in which W or Mo added with glass or a common material is arranged. The surface layer ceramic green sheet before lamination which constitutes this is composed of a W or Mo conductor and a W or Mo conductor.
It has a conductor wiring structure in which conductors to which glass or common material is added are connected.

[0005]

[Problems to be Solved by the Invention]

However, in the above-mentioned method for manufacturing a multilayer ceramic wiring board, when the conductor wiring is formed by applying the photolithography method, fine conductor wiring can be formed with a narrow pitch, but the fine conductor has conductive resistance and metallization. Inferior strength. The Ag conductor in the low temperature fired substrate is
When the wiring interval becomes narrow, the surface Ag conductor has the property of easily migrating (diffusing) in the glass contained in the low temperature fired substrate under humidity, and the insulation of the insulating layer deteriorates when a voltage is applied under humidity. As described above, the required characteristics cannot be satisfied due to the miniaturization or narrow pitch of the conductor wiring.

On the other hand, in order to satisfy required characteristics such as conduction resistance of conductor wiring, metallizing strength and solder wettability,
When the conductor wiring formed on the ceramic green sheet is formed of two or more kinds of conductors having partially different compositions, it is very difficult to connect the conductors by the conventional thick film printing method, and the positional deviation occurs. appear. Further, expansion and contraction of the printing screen and bleeding of the printing paste have been a limitation in miniaturizing the conductor wiring or narrowing the pitch.

The present invention was devised in response to the above-mentioned problems, in which a fine wiring conductor of a multilayer ceramic wiring substrate is formed by a photolithography method using a photosensitive paste, and a narrow pitch at that time is formed. The present invention provides a method for manufacturing a multilayer ceramic wiring board that satisfies the required characteristics such as improvement of migration resistance related to fine wiring, conduction resistance, metallization strength and solder wettability.

[0009]

As a method for solving the above problems, the method for manufacturing a multilayer ceramic wiring board according to the present invention has two or more kinds of conductor wirings partially different in composition. In a method of manufacturing a multilayer ceramic wiring board obtained by laminating one or more green sheets and one or more other green sheets respectively, and firing the same, two or more kinds of photosensitive pastes made of respective conductor composition powders on the ceramic green sheets. And a photosensitive paste coating step of uniformly coating the photosensitive paste coating film so as to fill the area where each conductor wiring is formed, and a conductive paste portion of the photosensitive paste coating film. An exposure step of selectively irradiating ultraviolet rays with a light-shielding mask, and a portion of the photosensitive paste coating film which is not irradiated with ultraviolet rays, with a predetermined developing solution. The method further includes a developing step of further dissolving and removing, and a step of firing a green sheet having two or more kinds of conductor wirings having partially different compositions, laminated with another green sheet, and then fired. And a method for manufacturing a multilayer ceramic wiring board.

Further, in another method for manufacturing a multilayer ceramic wiring board according to the present invention, in the coating step, the portions where the respective photosensitive paste coating films overlap with each other are pressed by a mechanical press to be flat, and a light-shielding mask in the exposure step. And a method for manufacturing a multilayer ceramic wiring board, which is characterized by improving adhesion with

[0011]

In the method for manufacturing a multilayer ceramic wiring board of the present invention, the conductor wiring is formed by a photolithography method using a photosensitive paste, so that the pattern bleeding due to the paste viscosity as seen in the conventional thick film printing method is prevented. Does not occur. Therefore, it is possible to form fine conductors with a narrow pitch and excellent dimensional accuracy. Furthermore, since there is no stretching of the screen plate as seen in the thick film printing method, the conductor can be formed with high positional accuracy. On the other hand, as a method of forming two or more kinds of conductor wirings having partially different compositions in order to improve conduction resistance, metallization strength and the like and to prevent migration,
Conductor wiring is performed by one photolithography process (exposure to development) through a coating process in which the photosensitive paste is uniformly filled so as to fill the area where each conductor is formed, and the photosensitive paste coating films are overlapped with each other. Therefore, the difficult alignment for connecting the conductors, which is required in the thick film printing method, is unnecessary. Therefore, the positioning of two or more different conductors is completed, the limit of miniaturization is improved, and reliability as a conductor is also obtained. Further, since it is not necessary to align the conductors with each other, the working efficiency and the yield can be improved.

Further, in the coating step, the areas where the respective photosensitive paste coating films overlap each other are flattened by a mechanical press to improve the close contact with the light-shielding mask in the exposure step, and increase the pattern size due to the leakage of ultraviolet rays. It is possible to suppress, and it works so as to further improve the dimensional accuracy, the narrow pitch, and the limit of miniaturization. Also, it acts to suppress the delamination of the conductor connecting portion which is an inner layer when the green sheets are laminated.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below in detail with reference to the drawings. 1 is a schematic cross-sectional view of a ceramic package of an embodiment of the present invention, FIG. 2 is a plan view of a first conductor pattern and a second conductor pattern of an embodiment of the present invention, and FIG. An example is shown, (a) is the first
Photosensitive paste a on the conductor pattern portion of the
FIG. 4 is a plan view showing a range in which the photosensitive paste b is applied to the conductor pattern portion of FIG. 4, FIG. 4 shows an embodiment of the present invention, and (a) shows an overlapping portion of the coating films of the photosensitive paste a and the photosensitive paste b. FIG. 5B is a cross-sectional view to be described, FIG. 5B is a cross-sectional view of an overlapping portion flattened by a mechanical press, and FIG. 5 is an exploded perspective view showing an example of stacking ceramic packages.

First, referring to FIG. 5, a ceramic package 100 (PG
An example of stacking A) will be described. The conductor wiring system of the ceramic package 100 is composed of a power supply line, a ground line and a signal line. The fine wiring is often used as the surface wiring 105 such as a wire bond portion, and at the same time, a part of the conductor becomes the inner wiring 104. Therefore, in the following embodiments, a method of forming fine wirings, which are simultaneously connected to each other, using the surface wiring 105 as the first conductor pattern and the inner wiring 104 as the second conductor pattern will be described.

Next, the sectional structure of the ceramic package of this embodiment will be described with reference to FIG. 2 in which the first conductor pattern 1 and the second conductor pattern 2 are formed
Above and below the green sheet 3 of the third layer, the green sheet 4 of the first layer and the green sheet 5 of the third layer are arranged in three layers.
A ceramic green sheet is thermocompression bonded to obtain a laminated product. Next, after firing at 800 to 1000 ° C., the input / output pin 7 is brazed to obtain a ceramic package. Here, the conductor connecting portion 14 of the first conductor pattern 1 and the second conductor pattern 2 is configured to be an inner layer wiring.

Next, with reference to FIG. 2, a plan view of the conductor wiring composed of the first conductor pattern 1 and the second conductor pattern 2 of this embodiment will be described. The first conductor pattern 1 is a surface wiring that is wire-bonded, and is a portion where the finest wiring is concentrated. It is also a part where strict required characteristics such as migration resistance and metallization strength described above are required. The second conductor pattern 2 is an inner layer wiring and is preferably a conductor having low conduction resistance.

Further, referring to FIG. 3, a description will be given of the range in which the photosensitive paste of each of the first conductor pattern 1 and the second conductor pattern 2 of this embodiment is applied. The area where each photosensitive paste is applied should be applied uniformly so as to fill the area where each conductor wiring is formed. Also, from the viewpoint of saving paste, the minimum necessary range is desirable. In this embodiment, the photosensitive paste a is applied to the first conductor pattern portion in the range 12 in FIG. 3 and the photosensitive paste b is applied to the second conductor pattern portion in the range 13 in the figure by a general thick film printing method. Applied. The size of the coating range is 1 from the specified position (the boundary between the inner layer wiring and the surface layer wiring) for the outer dimension of the photosensitive paste a.
Increase by 0 μm to 3 mm. This means that a part of the first conductor pattern 1 (surface layer wiring) has a connecting portion with the second conductor pattern 2 as an inner layer wiring, as described above, and stabilizes the migration resistance and the metallization strength. This is because it is obtained. Therefore, if the thickness is 10 μm or more, the photosensitive paste b may squeeze out or shift to the surface layer portion, and migration resistance and metallization strength cannot be stably obtained. On the other hand, if it is 3 mm or more, a large amount of unnecessary paste is required, the number of the first conductor patterns 1 having high conduction resistance increases, and the conduction resistance also deteriorates, which is not preferable. Desirably, the thickness is 50 μm to 500 μm. Further, the inner dimension of the photosensitive paste a is the first conductor pattern 1
10 μm to 500 μm larger than the tip portion of. 10μ
If the thickness is less than m, the first conductive pattern 1 may be damaged due to bleeding or deviation of the photosensitive paste a.
If it is more than m, a large amount of unnecessary paste is required, which is not preferable. Desirably, the thickness is 50 μm to 100 μm. Next, the external dimensions of the photosensitive paste b are the same as those of the second conductor pattern 2
10 μm to 500 μm larger than the tip portion of. 10μ
If the thickness is less than m, the second conductive pattern 2 may be damaged due to printing or displacement of the photosensitive paste b.
If it is more than m, a large amount of unnecessary paste is required, which is not preferable. Desirably, the thickness is 50 μm to 100 μm. Furthermore, the inner dimension of the photosensitive paste b is made smaller by 10 μm to 3 mm from the specified position (the boundary between the inner layer wiring and the surface layer wiring).
This is the first conductor pattern 1 (surface wiring) as described above.
This means that a part of the above has a connecting portion with the second conductor pattern 2 as an inner layer wiring, and is for ensuring stable migration resistance and metallization strength. Therefore, when the thickness is 10 μm or less, the photosensitive paste b may be squeezed out to the surface layer portion due to printing or misalignment, and migration resistance and metallization strength guidance cannot be stably obtained. On the other hand, if the thickness is 3 mm or more, a large amount of unnecessary paste is required and the conduction resistance becomes poor, which is not preferable. Preferably 5
0 μm to 500 μm is preferable. Further, the overlapping portion 11 of the photosensitive paste a and the photosensitive paste b needs to be 5 μm to 1 mm. This is because if the overlapped portion 11 is 5 μm or less, there is a risk of wire breakage due to printing bleeding of the photosensitive paste, misalignment, scraping, and the like. On the other hand, if the thickness is 1 mm or more, the number of the first conductor patterns 1 increases and the conduction resistance deteriorates, which is not preferable. It is preferably 20 μm to 100 μm.

Example 1 The first example is a ceramic package (PGA) that can be fired at a low temperature of 800 to 1000 ° C., and the surface layer is made of Ag-Pd, which is the first conductor pattern, and is durable. A conductor with excellent migration properties is placed, and the second layer is used for the inner layer.
2 is an example in which a conductor mainly composed of Ag, which is the conductor pattern of FIG. First, the low temperature fired ceramic materials used in the present invention are SiO ₂ -B ₂ O ₃ based to PbO-SiO ₂ -A.
l ₂ O ₃ -B ₂ O ₃ based glass, _CaO-SiO 2 -Al
₂ O ₃ -B ₂ O ₃ based glass or the like _Al 2 _O 3, glass was added aggregate component such as SiO ₂ - ceramic composite system or MgO
-Al ₂ O ₃ -SiO ₂ based crystallized glass, and the like. Next, this powder is mixed with an organic binder, a plasticizer, a solvent and the like in a ball mill to form a slurry, and then a green sheet is obtained by a doctor blade method. The conductor paste is prepared by thoroughly mixing Ag or Ag-Pd powder with a negative photoresist on a three-roll mill. A
Pd in the g-Pd paste is used in an amount of 5 parts by weight or more for the purpose of suppressing electromigration of Ag. However, since the conduction resistance is high, it is preferably 30 parts by weight or less. In the first embodiment, the first conductor pattern is Ag-20 wt% Pd.
It was used. The process of forming the first conductor pattern 1 and the second conductor pattern 2 on the low temperature fired ceramic green sheet with the above-described structure and dimensions will be described below.

-Photosensitive Paste Coating Step-This step is a step of separately coating the green sheet with the photosensitive paste. On the green sheet in which the through holes are formed as necessary and the conductors are filled, the photosensitive paste a is applied to the first conductor pattern portion by the thick film printing method within the range of FIG. The photosensitive paste b was applied to the area within the range of FIG. 3 (b) to obtain a coating film having a thickness of 20 μm. The size of the coating range is within the range described in FIG. 3, the outer dimension of the photosensitive paste a is increased by 200 μm from the specified position (the boundary between the inner layer wiring and the surface layer wiring), and the inner dimension is the first dimension. It was made 100 μm larger than the tip of the conductor pattern. Further, the outer dimension of the photosensitive paste b is 100 μm larger than the tip of the second conductor pattern, and the inner dimension is 100 μm from the specified position (the boundary between the inner layer wiring and the surface layer wiring).
I made it smaller. At this time, the overlapping portion of the photosensitive paste a and the photosensitive paste b was 100 μm. The order in which the photosensitive paste a and the photosensitive paste b are applied is not particularly limited, but it is advantageous to apply the photosensitive paste a after applying the photosensitive paste b, because bleeding is small.

-Exposure Step-This step is a step of selectively irradiating the coating film of the photosensitive paste with ultraviolet rays. After the photosensitive paste applied in the previous step is dried, the green sheet and the light shielding mask are aligned with each other, and the conductor pattern portion (wiring portion in FIG. 2) is selectively irradiated with ultraviolet rays through the light shielding mask.

-Developing Step-This step is a step of developing and removing the coating film of the photosensitive paste which is not irradiated with ultraviolet rays to obtain a conductor pattern.
The coating film of the photosensitive paste in which the conductor pattern portion is selectively irradiated with ultraviolet light in the previous step is immersed and shaken in a predetermined developing solution to dissolve and remove the portion other than the conductor pattern portion.

The desired conductor pattern on the green sheet thus obtained is pressure-bonded to another green sheet by the hot pressure bonding method to be laminated. And after baking this laminated body at 900 degreeC in the atmosphere, 42 alloy (Ni-Co-Fe)
Alternatively, an I / O pin made by Cover was adhered to a portion with a lead wire to prepare a 208-pin ceramic pin grid array package (PGA).

Next, characteristics of the low temperature fired ceramic substrate according to the present invention will be described in comparison with a conventional ceramic substrate. Table 1 shows the evaluation results of observing the state of the conductor connecting portion 14 using Ag-Pd as the surface wiring, and the occurrence of migration when a voltage of 50V DC is applied after exposure to high temperature and high humidity of 85 ° C and 80% humidity. Indicates. Further, as a comparative example of the surface wiring according to the present invention, the measurement results of the surface wiring formed by the thick film printing method are also shown together.

[Table 1] As is clear from the above evaluation results, in the surface wiring of the present invention, no displacement or bleeding is observed in the conductor connecting portion. Even if the conductor interval is narrowed, very good migration resistance was obtained.

EXAMPLE 2 In the second example, Mo (melting point 2622 ° C.) and W (melting point 33), which are refractory metal materials, are formed on an alumina green sheet.
A method of forming a conductor wiring made of, for example, 82 ° C.) and manufacturing a ceramic package (PGA) will be described. In this embodiment, a conductor having excellent metallization strength, which is mainly composed of W which is the first conductor pattern and a co-material (alumina, glass or a mixed powder of alumina and glass), is arranged on the surface wiring, and a second conductor is formed on the inner layer. This is an example in which a conductor made of pure W is arranged for the purpose of reducing conduction resistance which is a conductor pattern.
The alumina ceramic material used in the present invention is 92% alumina ceramics. This alumina powder, an organic binder, a plasticizer, a solvent and the like are mixed in a ball mill to form a slurry, and a green sheet is obtained by a doctor blade method. Further, the conductor paste is W or a co-material with W (alumina, glass or a mixed powder of alumina and glass).
Is mainly mixed with a negative photoresist by a three-roll process. The co-material in the first conductor pattern is used in an amount of 1 part by weight or more in order to secure metallization strength. However, since the conduction resistance increases as the proportion increases, it is preferably 20 parts by weight or less. In Example 2, the first conductor pattern was prepared by adding 5 parts by weight of the common material to W powder. The steps, structure, and dimensions for forming the first conductor pattern and the second conductor pattern are the same as those in Example 1 except that the green sheet is alumina.
The same is the same except that the conductor pattern is a mixed powder of W and the co-material, and the second conductor pattern is W.

Next, the metallization characteristics of the alumina ceramic substrate according to the present invention will be described in comparison with a conventional ceramic substrate. Table 2 shows the state of the conductor connecting portion 14 and the evaluation of the bondability. 3 shows evaluation results obtained by measuring a conductor wiring according to the present invention and a surface wiring formed by a thick film printing method as a comparative example.

[Table 2] As is clear from the above measurement results, in the alumina ceramic substrate of the present invention, there was no displacement or bleeding in the conductor connecting portion 14, and it was possible to narrow the conductor width to 25 μm and the pitch to 50 μm. Further, good bonding property was obtained even in fine wiring with a conductor width of up to 50 μm.

Example 3 In the third example, in the photosensitive paste coating step of Example 1, a step of pressing the overlapping portions 11 of the photosensitive paste coating films with each other by a mechanical press is performed. is there. In Example 1, the overlapping portions 11 of the coating films of the photosensitive paste a and the photosensitive paste b were flatly pressed at 80 ° C. × 20 kg / cm ² by a mechanical press. By doing so, the overlapping portion of the photosensitive paste is flattened as shown in FIG. Therefore, the adhesion with the light-shielding mask in the subsequent exposure step is improved, and the expansion of the pattern dimension due to the leakage of ultraviolet rays can be suppressed. Further, when the green sheet having the formed surface wiring and another green sheet were laminated and pressure-bonded, it was possible to suppress the occurrence of delamination at the connecting portion.

Next, the width and variation σ of the conductor formed according to the present invention will be described in comparison with the conductor of Example 1 which is not subjected to mechanical pressing. Table 3 shows the conductor width and the variation σ. 1 shows the results of measurement of a conductor wiring according to the present invention, a conductor wiring not subjected to mechanical pressing of Example 1 as a comparative example, and a conventional conductor wiring obtained by a thick film printing method.

[Table 3] As is clear from the above measurement results, with the conductor wiring of the present invention, the limit of fine wiring formation was improved, and the conductor wiring with improved dimensional accuracy was obtained.

[0028]

According to the present invention, since the conductor wiring is formed by the photolithography method using the photosensitive paste, it becomes possible to form fine conductors with a narrow pitch with high dimensional accuracy, and to improve the performance of the multilayer ceramic wiring board. It is possible to support functionalization, high density, and miniaturization. Further, in the conductor wiring of the present invention, in order to improve conductor characteristics such as migration resistance and metallization strength, which are problems in a fine conductor with a narrow pitch, two or more kinds of conductor wirings having partially different compositions are positioned with high positional accuracy. Since they can be well connected, a multilayer ceramic wiring board using them can be manufactured at a good yield and at a low cost. Further, in the step of applying the photosensitive paste, the overlapping portions of the coating films are flattened by a mechanical press, whereby the limit of fine wiring formation with a narrow pitch is improved. Therefore, it is possible to further increase the functionality, increase the density, and reduce the size of the multilayer ceramic wiring board.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a ceramic package according to an embodiment of the present invention.

FIG. 2 is a first conductor pattern and a second conductor pattern according to an embodiment of the present invention.
3 is a plan view of the conductor pattern of FIG.

FIG. 3 shows an embodiment of the present invention, in which (a) shows a range in which the first conductive pattern portion is coated with the photosensitive paste a and (b) shows a range in which the second conductive pattern portion is coated with the photosensitive paste b. It is a top view shown.

FIG. 4 shows an embodiment of the present invention, (a) is a cross-sectional view for explaining an overlapping portion of coating films of a photosensitive paste a and a photosensitive paste b, and (b) is an overlapping flattened by a mechanical press. It is a sectional view of a part.

FIG. 5 is an exploded perspective view showing an example of stacking ceramic packages.

[Explanation of symbols]

1 ... 1st conductor pattern, 2 ... 2nd conductor pattern, 3 ... 2nd layer green sheet, 4 ... 1st layer green sheet, 5 ... 3rd layer Green sheet, 6 ... through hole, 7 ... input / output pin, 8 ...
..Bonding wires, 9 ... Semiconductor elements, 10.
..Adhesive, 11 ... Overlapping part, 12 ... Photosensitive paste a, 13 ... Photosensitive paste b, 14 ...
Conductor connection part, 100 ... Ceramic package, 10
3 ... I / O pins, 104 ... Inner layer wiring, 105 ...
..Surface layer wiring

Claims (2)

[Claims] 1. A method for producing a multilayer ceramic wiring board obtained by stacking one or more green sheets having two or more kinds of conductor wirings partially different in composition and another green sheet and firing the laminated layers. In order to uniformly fill the ceramic green sheet with two or more kinds of photosensitive pastes made of the respective conductor composition powders so as to fill the area where the respective conductor wirings are formed, and to make the respective photosensitive paste coating films overlap each other. A photosensitive paste coating step, an exposing step of selectively irradiating the conductive wiring portion of the photosensitive paste coating film with ultraviolet rays by a light-shielding mask, and a portion of the photosensitive paste coating film not irradiated with ultraviolet rays To
A developing step of dissolving and removing with a predetermined developing solution, and a step of laminating a green sheet having two or more kinds of conductor wirings having partially different compositions, which is obtained thereby, with another green sheet and then firing. A method of manufacturing a multi-layer ceramic wiring board, which comprises: 2. The method according to claim 1, wherein the portions where the respective photosensitive paste coating films are overlapped with each other are pressed by a mechanical press to be flattened to improve the adhesion with the light shielding mask in the exposure step. For manufacturing a multilayer ceramic wiring board.