JPH04328207A - Conductor compound and wiring board - Google Patents

Abstract

PURPOSE:To provide a conductor compound excellent in solder wettability and the bonding strength with circuit board by using three sorts of glass frit. CONSTITUTION:An Ag alloy with Pd and/or Pt is used as a conductor, and therewith a conductor compound is produced by dispersing an inorganic binder incl. glass frit in a vehicle. An amorphous glass of PbO-B2O3-SiO2-MnO2 type, a crystallized glass of ZnO-B2O3-SiO2-MnO2 type, and a low melting point glass of PbO-B2O3-SiO2-ZnO type are used to the glass frit, wherein their contents shall range 6-20wt.% for 100 parts by wt. conductor. According to this constitution, the compound excels in the solder wettability and gives good bonding strength with a circuit board at the initial stage and after aging. The circuit board can be prevented from deterioration after anti-moisture, and load aging, and generation of shortcircuit in thin wire patterns.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor composition for forming an external conductor on a wiring board on which an element such as a semiconductor integrated circuit is mounted, and a wiring board having an external conductor formed from this conductor composition.

0002

[Prior Art] In recent years, substrate materials and conductors have been heated to approximately 1000°C.
Development of wiring boards that can be obtained by co-firing at the following low temperatures is underway. The substrate material of such a low-temperature fired wiring board is mainly composed of an alumina glass composite. On the other hand, as the conductor material, instead of the conventional W or Mo, it is now possible to use an Ag-based material with low conduction resistance.

The internal conductor of such a wiring board is A.
However, since the outer conductor is soldered to the mounted component, the outer conductor is required to have good solder wettability, and Ag alloy-based materials are mainly used.

[0004] Furthermore, the adhesive strength after soldering must be sufficiently high both at the initial stage and after aging. Generally, aging deterioration is thought to be caused by the diffusion of Sn in the solder into the Ag. It needs to be something.

By the way, the conductor composition is obtained by dispersing conductive metal powder such as Ag-based metal powder and an inorganic binder containing glass frit in a vehicle.

In order to improve the solder wettability and adhesive strength, various proposals have been made for the glass composition of the glass frit in the conductor composition for the external conductor.
JP 62-32562, JP 63-207001
No., JP-A-64-86404, JP-A-1-29809
0 etc.).

By the way, such a wiring board usually has
After an internal conductor pattern is formed on a green sheet of substrate material, these are laminated and fired, an external conductor pattern is formed and fired, and a resistor pattern is further formed and fired. The resistor pattern is formed by printing a resistor composition in which conductor or resistor particles and an inorganic binder containing glass frit are dispersed in a vehicle.

[0008] As described above, when a resistor pattern is printed and fired on an external conductor pattern after firing, the glass in the conductor and the glass in the resistor react, causing a bleed-out phenomenon in which the glass in the conductor is pushed out. There is a problem in that the electrical characteristics of the resistor are adversely affected. In particular, in high-density wiring boards with fine wiring patterns and thin film thickness, short circuits are likely to occur due to this bleed-out phenomenon. Further, due to aging or moisture-resistant load aging, migration is likely to occur, reducing reliability.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductor composition and a wiring board that have excellent solder wettability, high adhesive strength, and are prevented from bleed-out.

0010

[Means for Solving the Problems] Such objects are achieved by the present invention having the following configurations (1) to (8).

(1) A conductor composition in which a conductor containing Ag, Pd and/or Pt, and an inorganic binder containing a glass frit are dispersed in a vehicle, wherein the glass frit is PbO-B2O3-SiO2- MnO
2-based amorphous glass and ZnO-B2O3-Si
O2-MnO2-based crystallized glass and PbO-B2
O3 -SiO2 -ZnO-based low melting point glass, and the glass frit has a melting point of 6 to 2 with respect to the conductor.
A conductor composition characterized in that it contains 0 wt%.

(2) The glass composition of the glass frit is 30 to 50 wt% PbO and 10 to 50 wt% B2O3.
25wt%, SiO2 5-15wt%, MnO2
The conductor composition according to (1) above, which contains 1 to 20 wt% of ZnO and 8 to 25 wt% of ZnO.

(3) The conductor composition according to (1) or (2) above, wherein the ratio of the crystallized glass to the amorphous glass is 0.2 to 0.85 by weight.

(4) The conductor composition according to any one of (1) to (3) above, which contains the low melting point glass in an amount of 1 to 4 wt% based on the conductor.

(5) The inorganic binder further contains T.
iO2, ZrO2, CoO, NiO, Al2O3
, Bi2 O3 and Sb2 O3 in an amount of 10 ppm to 2
The conductor composition according to any one of (1) to (4) above, containing wt%.

(6) A wiring board in which an external conductor is formed using the conductor composition according to any one of (1) to (5) above.

(7) The above (6) having a resistor containing 35 to 95 wt% of glass in contact with the outer conductor.
).The wiring board described in ).

(8) The glass is amorphous glass.
The wiring board according to (7) above, containing 0 wt% or more.

[0019]

[Operation] In the present invention, the glass frit component of the conductor composition is PbO-B2 O3 -SiO2 -MnO2-based amorphous glass, ZnO-B2 O3 -SiO2 -Mn
O2-based crystallized glass and PbO-B2 O3 -S
The mixture contains iO2-ZnO2-based low melting point glass in a predetermined proportion.

The presence of crystallized glass in this way makes it possible to suppress the reaction between the glass component in the external conductor and the glass component in the resistor, thereby preventing the occurrence of the bleed-out phenomenon of the glass in the conductor. is prevented. As a result,
Deterioration of electrical characteristics after humidity-resistant load aging can be prevented. In addition, the pattern of the conductor layer is, for example, 200 μm.
The occurrence of short circuits can be effectively prevented even in a high-density wiring board with a thin line pattern and a thin film thickness as described below.

[0021] Further, by using such a glass composition, the solder wettability is also sufficient. Furthermore, the adhesive strength after soldering is sufficient both at the initial stage and after aging. In particular, it is possible to prevent Sn in the solder when a conductor element or the like is soldered from diffusing into the conductor and reducing the adhesive strength between the substrate and the conductor.

[0022]

[Specific Configuration] The specific configuration of the present invention will be explained in detail below.

The conductor composition of the present invention contains Ag and Pd and/or Pt, which are the basic composition of the conductor. That is, it contains any one of Ag-Pd, Ag-Pt, and Ag-Pd-Pt alloys.

[0024] As described above, by using an Ag alloy, it is possible to obtain the effect of improving migration resistance and solder eating resistance in the case of Pd, compared to using Ag alone.
In the case of t, the effect of improving solder wettability can be obtained by adding a small amount.

[0025] In such an Ag alloy, Ag, Pd,
The proportion of Pt is determined appropriately depending on the purpose, but Ag-
In the Pd alloy, the Pd content is preferably 5 to 25 wt%. When the Pd content is less than 5 wt%,
This is because the effect of adding Pd cannot be obtained, and if it exceeds 25 wt%, the conductivity of the conductor deteriorates.

[0026] Furthermore, in the Ag-Pt alloy, the Pt content is preferably 0.5 to 5 wt%. If the Pt content is less than 0.5 wt%, the effect of Pt addition cannot be obtained, and if it exceeds 5 wt%, the conductivity of the conductor deteriorates.

In addition, in the Ag-Pd-Pt alloy, the Pd content is 5 to 25 wt%, and the Pt content is 0.5 wt%.
It is preferable to set it to 5 wt%. With such a content, the effects of adding Pd and Pt can be obtained, and the conductor can also have sufficient electrical conductivity.

The conductor composition of the present invention is in the form of a paste, and in such a state Ag, Pd and/or Pt may exist separately. In this case, an Ag alloy is formed by subsequent firing.

[0029] Such an Ag alloy, or a metal that becomes an Ag alloy as described above, is usually present in the form of particles in a paste-like composition.

[0030] The average particle size of the Ag alloy particles is 0.01 to 1
It is preferable to set it to about 0 μm. This is because if the average particle diameter is less than 0.01 μm, the shrinkage rate of the conductor becomes too large, and if it exceeds 10 μm, the printability and dispersibility of the conductor composition deteriorate.

[0031] In addition, in the metal particles forming Ag alloy, A
The average particle size of g particles, Pd particles, and Pt particles is 0.0.
It is preferable to set it as about 1-10 micrometers. The reason is,
If the average particle size is less than 0.01 μm, as in the case of the Ag alloy particles described above, the shrinkage rate will be insufficient, and 10
This is because if it exceeds .mu.m, the effect of improving migration resistance due to the addition of Pd becomes small.

In the present invention, 6 to 20 wt%, preferably 8 to 20 wt% of glass frit is added as an inorganic binder to the conductor.
Contains 14wt%.

[0033] The glass frit in this case is PbO-B
2 O3-SiO2 -MnO2-based amorphous glass,
ZnO-B2 O3 -SiO2 -MnO2-based crystallized glass and PbO-B2 O3 -SiO2 -
It is a mixture of ZnO-based low melting point glasses.

The feature of the present invention is that these three types of glass are mixed, and the effects of the present invention can be obtained by setting the content of the glass frit within the above range.

When the glass frit content is less than 6 wt %, aging characteristics deteriorate, and when it exceeds 20 wt %, solder wettability becomes insufficient and a bleed-out phenomenon occurs.

Furthermore, the ratio of crystallized glass to amorphous glass is such that the weight ratio [crystalline glass/amorphous glass] is 0.2 to 0.85, preferably 0.4 to 0.75. It is better. By setting such a ratio, the bleed-out phenomenon can be better prevented. If it is less than 0.2, the effect of preventing the bleed-out phenomenon will decrease, and 0.85
If it exceeds 20%, solder wettability will be insufficient.

[0037] The content of the low melting point glass in the conductor is 1 to 4 wt%, preferably 2.5 to 3.5 wt%.
It is better to By setting such a ratio, solder wettability becomes good. If it is less than 1 wt%, solder wettability will deteriorate. Moreover, if it exceeds 4 wt%, no effect on solder wettability will be observed and a bleed-out phenomenon will occur.

[0038] Furthermore, the proportions of each oxide, which is the main component of each glass, are as follows expressed in wt%;
The softening points are as follows.

[0039]The softening point is 3.5 x 3.5 x 12 m.
Measurements were made using differential thermal expansion using a sample of m and a load of 3 g.

(1) Amorphous glass PbO(55-65)-B2O3(15-25)-
SiO2 (5-15)-MnO2 (5-15) Softening point 450-520°C, especially about 480°C

[0041](
2) Crystallized glass ZnO (55-65)-B2O3 (15-25)-
SiO2 (5-15)-MnO2 (5-15) Softening point 530-610°C, especially around 550°C

[0042](
3) Low melting point glass PbO (70-85)-B2 O3 (8-12)-S
iO2 (1-3)-ZnO (3-10) Softening point around 300-400℃

The glass frit of the present invention is a mixture of three types of glass as described above, and the proportions of each oxide constituting this glass frit are as follows.

PbO: 30-65 wt%, preferably 45-60 wt% B2 O3: 10-25 wt%, preferably 14-60 wt%
20wt%SiO2: 5-15wt%, preferably 7-11wt%MnO2: 1-20wt%, preferably 3-15wt%ZnO: 8-25wt%, preferably 10-20wt%

[0045] By setting the content as above, the effects of the present invention can be obtained.

When PbO is less than 30 wt%, the aging properties tend to be insufficient, and when it exceeds 65 wt%, a bleed-out phenomenon occurs.

[0047] Furthermore, even if B2O3 is less than 10 wt%, the aging properties tend to be insufficient;
If it exceeds 5 wt%, a bleed-out phenomenon will occur. Further, even if the SiO2 content is less than 5 wt%, the aging properties tend to be insufficient, and if it exceeds 15 wt%, a bleed-out phenomenon occurs. Further M
Even if nO2 is less than 1 wt%, aging characteristics tend to be insufficient, and if it exceeds 20 wt%, solder wettability deteriorates. Furthermore, if the ZnO content is less than 8 wt%, a bleed-out phenomenon occurs, and if it exceeds 25 wt%, the solder wettability deteriorates.

[0048] Such glass has a thickness of 0.1 to 10 μm.
It is used as a powder with an average particle size of

When the average particle size is less than 0.1 μm, contamination with impurities during pulverization becomes significant, and when it exceeds 10 μm, printability tends to deteriorate.

Furthermore, in the present invention, in addition to glass frit, TiO2, ZrO2, and CoO2 are used as inorganic binders.
, NiO, Al2O3, Bi2O3 and Sb
At least one compound selected from 2 O3 is added. The amount added at this time is 10 ppm to the conductor.
It is preferable to set it to ~2wt%. By adding the above compound in the above range, solder wettability and aging characteristics can be further improved. If it is less than 10 ppm, the effect of improving aging characteristics will be reduced, and if it is less than 2wt.
%, solder wettability becomes insufficient.

Vehicles used in the present invention include binders such as ethyl cellulose, nitrocellulose, and acrylic resins, solvents such as terpineol and butyl carbitol, other dispersants, and activators. Any one of these may be used. It is added as appropriate depending on the purpose.

[0052] Generally, the content of the vehicle in the conductor composition is about 10 to 70 wt%.

The conductor composition of the present invention is prepared by mixing the above-mentioned Ag alloy grains or metal grains of Ag grains and Pd grains and/or Pt grains with the above-mentioned inorganic binder containing glass frit, and adding a binder, It can be obtained by adding a vehicle such as a solvent and kneading these to form a slurry. Here, the viscosity of the paste composition is 30,000 to 300,000 cp.
It is best to prepare it in advance.

The conductor composition of the present invention is used by printing a predetermined pattern on a substrate and baking it.

FIG. 1 shows an example of the structure of a multilayer wiring board in which the conductor composition of the present invention is used as an external conductor. FIG. 1 is a partial cross-sectional view of a multilayer wiring board.

As shown in the figure, the multilayer wiring board 1 is made up of an insulating substrate 4 in which a plurality of layers are laminated and integrated by firing.
An internal conductor 2 having a predetermined pattern is formed inside the substrate 4, and an external conductor 3 is formed at a portion of the internal conductor 2 exposed on the surface of the substrate 4.

The constituent materials of the substrate 4 include alumina-borosilicate glass, alumina-lead borosilicate glass, alumina-barium borosilicate glass, alumina-calcium borosilicate glass, and others that can be fired simultaneously with the internal conductor 2 and the like. Low temperature sintered materials containing oxide aggregate and glass such as alumina-strontium borosilicate glass and alumina-magnesium borosilicate glass are preferred.

[0058] In such a substrate material, the glass content is generally preferably about 50 to 80 wt%.

The internal conductor 2 is usually multi-layered and connected to the substrate 4.
They are electrically connected to each other via a through hole 5 formed in the thickness direction.

The external conductor 3 is formed on the surface of the substrate 4,
It is used as a pad for soldering surface-mounted components 7 such as chip components such as chip inductors and chip capacitors, semiconductor integrated circuit elements, elements such as diodes, etc. with solder 6, or for conduction to resistor 8. . Note that an insulating coating layer may be formed to cover the surface.

The conductor composition of the present invention is applied to form the above-mentioned outer conductor 3.

Note that the internal conductor 2 is preferably made of a conductor mainly composed of Ag, particularly Ag, since good conductivity is given priority. The internal conductor composition contains a conductor and a glass frit in an amount of about 5 to 10 wt% based on the conductor.

Further, the film thickness of the internal conductor 2 is usually 5 to 20 mm.
The film thickness of the outer conductor 3 is usually 5 to 20 μm.
It is considered to be a degree. The conduction resistance of the inner conductor and outer conductor depends on their composition, but generally the former is 2 to 1
The latter is preferably about 10 to 30 mΩ/□.

Furthermore, the resistor 8 contains a resistor such as ruthenium oxide, lead ruthenium pyrochlore, and glass frit. The particle size of the resistor particles is 0.05 to 0.5μ
The glass frit content is about 35 to 95 wt% with respect to this resistor.

[0065] Glass frit is generally made of PbO45-6
0wt%, B2O3 10-20wt%, SiO
2 20-30wt%, ZnO 0-8wt%,
The softening point is about 450 to 600℃, and in the glass frit,
Amorphous glass is contained in an amount of 90 wt% or more. and,
According to the present invention, the bleed-out phenomenon of the glass frit in such a resistor can be effectively prevented.

[0066] Such a multilayer wiring board is manufactured, for example, as follows.

First, a green sheet to be used as a substrate material is prepared.

This green sheet is made by mixing a predetermined amount of aggregate such as alumina powder, which is the raw material for the substrate, and glass powder (for example, borosilicate glass), adding a binder resin, a solvent, etc. to this, and kneading these. The slurry is made into a slurry, and a predetermined number of green sheets having a thickness of about 0.1 to 0.3 mm are produced by, for example, a doctor blade method.

Next, through holes 5 are formed in the green sheets using a punching machine or a mold press, and then a composition for internal conductors is printed on each green sheet by, for example, a screen printing method to form internal conductors in a predetermined pattern. A layer is formed and the through hole 5 is filled.

[0070] Next, the green sheets were stacked and heat pressed (approximately 40 to 120°C, 50 to 1000 kgf/c).
m2) to form a laminate of green sheets, and if necessary, the binder is removed, cutting grooves are formed, etc.

[0071] Thereafter, the green sheet laminate is baked and integrated in normal air at a temperature of about 800 to 1000°C to obtain a multilayer wiring board in which the internal conductor 2 is formed on the board 4.

Then, the external conductor paste is printed by screen printing or the like and fired to form the external conductor 3. Furthermore, the resistor material paste is printed and fired to form the resistor 8. Note that these external conductors 3 and resistors 8 may be formed by integrally firing with the substrate 4. However, when printing and firing on the substrate after firing the substrate, the adhesive strength will be low, but by applying the present invention, the adhesive strength will be extremely high.

Thereafter, predetermined surface mount components 7 are soldered to the external conductor 3, and if necessary, an insulating coating layer is formed to obtain the multilayer wiring board 1 shown in FIG.

Note that the substrate may also be produced by a printing method instead of the green sheet method described above.

[0075] Above, an example in which the present invention is applied to a multilayer wiring board has been described, but the present invention is not limited to this, but can also be applied to a single layer board such as a co-fired wiring board. can.

[0076]

[Examples] Specific examples of the present invention will be described below.

Example 1 (1) Preparation of conductor composition To 100 parts by weight of a conductor of a conductor composition having the component composition shown in Table 1, an ethyl cellulose resin and a high boiling point solvent (terpineol) were added as a vehicle. 20～
Add 40 parts by weight and knead to obtain conductor compositions 1 to 10 in Table 1.
I got it.

[0078] The conductor was added to form an Ag alloy during firing, and the Ag particles had an average particle size of 10 μm, and the Pd
The particles used were 1 μm, the Pt particles were 1 μm, the glass had an average particle size of 8 μm, and the oxide additive had an average particle size of 5 μm.

[0079]

[Table 1]

Table 1 also shows the ratio (weight ratio) of crystallized glass to amorphous glass in the glass frit and the ratio (wt%) of low melting point glass to the conductor.

Table 2 also shows the compositions of the amorphous glass, crystallized glass, and low melting point glass used.

[0082]

[Table 2]

(2) Preparation of green sheet With a composition of α-alumina: 40 wt% and glass powder: 60 wt%, the thickness is 1.
A green sheet with a diameter of 00 to 300 μm was produced (the glass in this case was Al2 O3 -B2 O3 -SiO
2 -MO system, where M=Ca, Ba, Sr, Mg).

(3) Preparation of resistor paste RuO2 (
9.1 wt% of glass powder (particle size 0.1 μm)
．． 8wt%, 4.1w of ZrSiO4 as an additive
t%, CuO, MnO and Nb2O as TCR modifiers
A resistor paste was prepared using 9wt% of 5 and 5 in total. Glass composition is PbO47.8wt%, B2O
3 16.7wt%, SiO2 27.8wt%,
Amorphous glass containing 5 wt% ZnO and 5.2 wt% Al2O3 was used.

(4) Preparation of wiring board After forming an Ag internal conductor on the green sheet, the green sheets were laminated by hot pressing to obtain a green sheet laminate. after that,
After degreasing this laminate, a wiring board was obtained by co-firing in air at a temperature of 900°C.

[0086] A conductor composition was applied to this wiring board by screen printing at a shrinkage rate of 15%, and the dimensions after firing were 2 mm ×
The pad was printed to a thickness of 2 mm and a film thickness of 12±2 μm, and baked at 850° C. in air.

For each of the obtained substrates, the adhesive strength of the conductor at the initial stage and after aging, and the solder wettability of the conductor were examined as follows.

(a) Adhesive strength test The test was conducted according to DuPont's peel test. Stretch a copper wire with a diameter of 0.8 mm in the horizontal direction of the conductor film and solder the part that overlaps with the conductor film, and then connect the copper wire extending from one end of the soldered end to the conductor film almost perpendicular to the surface to which the conductor film is applied. The membrane was pulled in the direction of peeling using a tensile tester, and the load at the time of peeling was read. For aging, the sample was left in a constant temperature bath at 150° C. for a predetermined period of time, and the load was read in the same manner.

(b) Solder wettability Each sample was immersed in molten solder at 230° C. for about 5 seconds, and evaluated based on the wetted area ratio of the pad.

Further, a conductor composition was printed on the same wiring board as above and fired to form a conductor layer having a fine line pattern with a width of 200 μm and a thickness of 15 μm. Thereafter, the above-mentioned resistor paste was further printed on the wire ends on the conductor layer in a wider width than the conductor layer, and baked in the same manner as above.

Using this wiring board, the presence or absence of a bleed-out phenomenon was investigated as follows.

(c) Occurrence of bleed-out phenomenon The end portion of the thin wire conductor pattern near the resistor was observed using an optical microscope and evaluated on the following four scales. This evaluation is indicated by ◎, △, ×, and XX. ◎ No bleed-out at all △ Bleed-out observed at a distance of 10 μm or less × Bleed-out observed at a distance of 50 μm or less × × Bleed-out observed at a distance of more than 50 μm

[0093] These results are shown in Table 3. Note that Table 3 also shows the values of conductor resistance.

[0094]

[Table 3]

[0095]

Effects of the Invention The external conductor of the present invention has good solder wettability and sufficient adhesion strength to the substrate both initially and after aging. Furthermore, it is possible to prevent the occurrence of a bleed-out phenomenon, and it is possible to prevent short circuits between wirings and deterioration of electrical characteristics.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a multilayer wiring board manufactured using the conductor composition of the present invention.

[Explanation of symbols]

1 Multilayer wiring board 2 Internal conductor 3 External conductor 4 Board 5 Through hole 6 Solder 7　Surface mount parts 8 Resistor

Claims (8)

[Claims] 1. A conductor composition in which a conductor containing Ag and Pd and/or Pt and an inorganic binder containing a glass frit are dispersed in a vehicle, wherein the glass frit is PbO-B2O3-SiO2-MnO2.
system amorphous glass and ZnO-B2O3-SiO
2-MnO2-based crystallized glass and PbO-B2
O3 -SiO2 -ZnO-based low melting point glass, and the glass frit has a melting point of 6 to 20 with respect to the conductor.
A conductor composition characterized in that it contains wt%. 2. The glass composition of the glass frit is:
PbO30-65wt%, B2O3 10-25wt
%, SiO2 5-15wt%, MnO2 1-2
The conductor composition according to claim 1, wherein the ZnO content is 0 wt% and ZnO is 8 to 25 wt%. 3. The conductor composition according to claim 1, wherein the ratio of the crystallized glass to the amorphous glass is 0.2 to 0.85 by weight. 4. The low melting point glass is 1 to 1 with respect to the conductor.
The conductor composition according to any one of claims 1 to 3, containing 4 wt%. 5. The inorganic binder further comprises TiO2
, ZrO2, CoO, NiO, Al2O3, B
At least one of i2 O3 and Sb2 O3 is added in an amount of 10 ppm to 2 wt% relative to the conductor.
The conductor composition according to any one of claims 1 to 4, comprising: 6. A wiring board in which an outer conductor is formed using the conductor composition according to any one of claims 1 to 5. 7. In contact with the outer conductor, the glass is
The wiring board according to claim 6, further comprising a resistor containing up to 95 wt%. 8. The glass is 90wt amorphous glass.
% or more of the wiring board according to claim 7.