JP2001185857A - Multilayer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer wiring board with which crack on a connecting conductor charged in a through hole can be effectively prevented and resistance of this connecting conductor can be suppressed low. SOLUTION: Concerning a multilayer wiring board, a firs wiring layer 2 and the second wiring layer 3 are successively laminated on the upper surface of a substrate 1 while interposing an insulation layer 4 and the first wiring layer 2, and the second wiring layer 3 are electrically connected by a connecting conductor 6 inside a through hole 5 provided on the insulation layer 4. The connecting conductor 6 contains oxidized tungsten particles 7 just in 0.1 to 7.0 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board having a plurality of wiring layers laminated with an insulating layer interposed therebetween.

[0002]

2. Description of the Related Art Hitherto, a multilayer wiring board has been used for forming a head substrate such as an LED array head.

[0003] Such a conventional multilayer wiring board is, for example, shown in FIG.
As shown in FIG. 1, a first wiring layer 12 and a second wiring layer 13 are sequentially laminated on an upper surface of a substrate 11 made of glass, ceramic, or the like via an insulating layer 14 therebetween. By forming a through hole 15 in the insulating layer 14 located between the two wiring layers 13 and filling the inside thereof with the connection conductor 16, the first wiring layer 12 and the second wiring layer 13 are electrically connected to each other. I try to connect.

The first wiring layer 12 and the second wiring layer 13
And silver (Ag) or gold (A
u) or the like, and glass or the like is used as the material of the insulating layer 14. These layers are made of a conductive paste or a glass paste by using a conventionally known thick film method, for example, screen printing. Print on top of 11
It was formed by coating and baking it at a high temperature.

[0005]

However, in this conventional multilayer wiring board, the linear expansion coefficient of the glass or the like forming the insulating layer 14 is 0.5 × 10 ⁻⁶ / ° C. to 9 × 10 ^−6.
/ ° C, whereas the coefficient of linear expansion of silver, gold, etc. forming the connection conductor 16 is relatively large, from 10 × 10 ⁻⁶ / ° C to 35 × 10 ⁻⁶ / ° C. When formed by the film method, a large thermal stress is applied to the connection conductor 16 due to a difference in the amount of shrinkage between the insulating layer 14 and the connection conductor 16 due to the cooling after baking of the paste, and the stress in the through hole 15 is generated by the stress. A large crack was generated in the connection conductor 16, and as a result, there was a disadvantage that it was impossible to connect the first wiring layer 12 and the second wiring layer 13 well.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a multilayer wiring board according to the present invention has a first wiring layer and a second wiring layer interposed on an upper surface of the substrate. A multi-layer wiring board in which the first wiring layer and the second wiring layer are electrically connected by a connection conductor in a through hole provided in an insulating layer, and the connection conductor has tungsten oxide fine particles in the connection conductor. 0.1 wt% to 7.0 w
It is characterized by containing t%.

The multilayer wiring board of the present invention is characterized in that the tungsten oxide fine particles have a particle size of 0.05 μm to 5.0 μm.

Further, the multilayer wiring board of the present invention is characterized in that the tungsten oxide fine particles are distributed more in the peripheral region than in the central region of the connection conductor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a multilayer wiring board according to one embodiment of the present invention, and FIG. 2 is an enlarged view schematically showing a main part of FIG. 1, wherein 1 is a substrate, 2 is a first wiring layer, and 3 is a second wiring layer. Wiring layer, 4 is insulating layer, 5 is through hole, 6 is connection conductor, 7
Are tungsten oxide fine particles.

The substrate 1 is made of an electrically insulating material such as alumina ceramics, mullite, aluminum nitride, glass ceramics, quartz, alkali glass, non-alkali glass, etc., and has a first wiring layer 2, an insulating layer 4, It functions as a supporting base material for supporting the two wiring layers 3 and the like.

When the substrate 1 is made of, for example, alumina ceramics, an appropriate organic solvent and a solvent are added to and mixed with a ceramic raw material powder of alumina, silica, magnesia or the like to form a slurry. A ceramic green sheet (ceramic green sheet) is obtained by employing a doctor blade method, a calendar roll method, or the like, and thereafter, the green sheet is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.). Be produced.

On the upper surface of the substrate 1, a plurality of first
The wiring layer 2 and the plurality of second wiring layers 3 have an insulating layer 4 therebetween.
Is applied and laminated.

The first wiring layer 2 and the second wiring layer 3 are formed of silver, gold, an alloy thereof, or the like so as to form a predetermined pattern, and both wiring layers 2 and 3 will be described later. They are electrically connected to each other via the connection conductor 6.

The first wiring layer 2 and the second wiring layer 4 are respectively attached and formed on the upper surface of the substrate 1 and the upper surface of the insulating layer 4 by employing a conventionally known thick film method. That is, the first wiring layer 2 is made of, for example, an organic solvent
A conductive paste obtained by adding and mixing a solvent is formed by printing and applying on the upper surface of the substrate 1 by conventionally known screen printing or the like, and then baking at a high temperature (350 ° C. to 800 ° C.). 3 is to print and apply the same conductive paste as that used for forming the first wiring layer 2 on the upper surface of the insulating layer 4 by a conventionally known screen printing or the like, and then bake it at a high temperature (350 ° C. to 800 ° C.). Formed by

The linear expansion coefficients of these wiring layers 2 and 3 are as follows:
10 × 10 ^-6 when made of a conductive material containing silver as a main component
/ ° C. to 12 × 10 ⁻⁶ / ° C.

On the other hand, the insulating layer 4 interposed between the first wiring layer 2 and the second wiring layer 3 serves to electrically insulate the first wiring layer 2 from the second wiring layer 3. And 0.5
It is formed of a silicate glass or the like having a linear expansion coefficient of × 10 ⁻⁶ / ° C. to 9 × 10 ⁻⁶ / ° C.

The insulating layer 4 has through-holes 5 at predetermined locations, specifically, at locations where the electrically connected wiring layers 2 and 3 intersect each other. 5 is filled with a connection conductor 6.

When the line width of the first wiring layer 2 and the second wiring layer 3 is 50 μm, the through hole 5 is 1.5 times as large as that of the first wiring layer 2 and the second wiring layer 3.
It is formed in a circular shape having a diameter of about 75 μm to 400 μm corresponding to eight times, and holds the connection conductor 6 therein.

When the insulating layer 4 is made of silicate glass, a glass paste obtained by adding and mixing an appropriate organic solvent / solvent to silicate glass powder is applied to a conventionally known thick film method, for example, a screen. Through-hole 5 by printing etc.
Is formed by printing and applying over the entire upper surface of the substrate 1 excluding the formation location of, and baking it at a high temperature.

The connection conductor 6 filled in the through hole 5 of the insulating layer 4 is formed by the first wiring layer 2 and the second
The first wiring layer 2 is formed of the same material as the wiring layer 3, that is, silver, gold, or an alloy thereof.
Then, both wiring layers 2 and 3 are electrically connected by contacting the second wiring layer 3 on the upper surface side.

The connection conductor 6 is printed and filled with a conductive paste obtained by, for example, adding and mixing an appropriate organic solvent and solvent to silver powder into the through hole 5 of the insulating layer 4 by screen printing or the like. High temperature (350 ° C to 600 ° C)
The elasticity of the conductor portion of the connection conductor 6 is 6.9 × 10 ¹⁰ Pa to 8.0 × 10
^{This is} a large value of ¹⁰ Pa.

The connection conductor 6 contains only 0.1 wt% to 7.0 wt% of tungsten oxide fine particles 7 having an elastic modulus lower than that of a metal such as silver or gold forming the connection conductor.

As described above, the tungsten oxide fine particles 7 having a low elastic modulus are contained in the connection conductor 6 in an amount of 0.1 wt% to 7.0 wt%.
When the insulating layer 4, the first wiring layer 2, the second wiring layer 3, the connection conductor 8, and the like are formed by a conventionally known thick film method, cooling after baking a glass paste or a conductive paste is performed. Accordingly, even if a thermal stress due to the difference in the amount of contraction between the connection conductor 6 and the insulating layer 4 is applied, the stress can be favorably alleviated and absorbed by the deformation of the tungsten oxide fine particles 7, whereby the connection With no cracks in the conductor 6, the first wiring layer 2 and the second wiring layer 3 can be electrically connected in a good state.

If the content of the tungsten oxide fine particles 7 is smaller than 0.1 wt%, the insulating layer 4, the first wiring layer 2, the second wiring layer 3 and the like may be formed by a conventionally known thick film method. When the thermal stress applied to the connection conductor 6 cannot be sufficiently reduced, and when the content is more than 7.0 wt%, the conduction resistance of the connection conductor 6 increases, so that the connection conductor 6 is energized. In this case, there is a disadvantage that the power lost in this portion is extremely large.

Accordingly, the content of the tungsten oxide fine particles 7 present in the connection conductor 6 is 0.1 wt% to 7.0 w
It must be set within the range of t%.

If the tungsten oxide fine particles 7 are distributed more in the peripheral region than in the central region of the connection conductor 6, the tungsten oxide particles near the interface between the insulating layer 4 and the connection conductor 6 where the thermal stress becomes maximum will be formed. Since the fine particles 7 are concentrated, there is an advantage that stress can be more effectively absorbed and reduced.

Therefore, the tungsten oxide fine particles 7
Is preferably distributed more in the peripheral area than in the central area of the connection conductor 6.

The tungsten oxide fine particles 7 include:
Particles having a particle size of 0.05 μm to 5.0 μm are preferably used, and the tungsten oxide fine particles 7 are made of tungsten (W).
Are formed by heating the metal fine particles made of at a relatively low temperature of about 300 ° C. for a predetermined time and oxidizing them.

The above-mentioned tungsten oxide fine particles 7 are
The connection conductor 6 can be formed at the same time when the connection conductor 6 is formed by the above-mentioned thick film method.

For example, tungsten fine particles (particle diameter: 0.05 μm to 5.0 μm) are contained in the conductive paste serving as the connection conductor 6.
μm) is added and mixed in an amount of 0.1 wt% to 5.0 wt%, and a part or all of these tungsten fine particles are chemically reacted with oxygen or the like in the air when the conductive paste is baked to oxidize. The tungsten fine particles 7 are formed in a state of being dispersed in the connection conductor 6. In order to distribute the tungsten oxide fine particles 7 more in the peripheral region than in the central region of the connection conductor 6, the connection conductor 6 is formed as described above. When forming by the thick film method, two kinds of conductive pastes having different contents of tungsten fine particles are prepared, and a conductive paste having a low content of tungsten fine particles is covered with a conductive paste having a high content of tungsten fine particles. Thus, these are realized by filling the inside of the through holes 5.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, a multilayer wiring board in which two wiring layers are stacked has been described, but the present invention is also applicable to a multilayer wiring board in which three or more wiring layers are stacked.

[0033]

[Experimental Example] Next, the operation and effect of the present invention will be described based on an experimental example. First, nine types of multilayer wiring board samples (sample Nos. 1 to 5) each containing a predetermined amount of tungsten oxide fine particles 7 having an average particle diameter of 1.0 μm in a connection conductor 6 having a diameter of 250 μm and a thickness of 30 μm mainly containing silver. 12) was prepared.

These sample Nos. 1 to 12 are composed of a first wiring layer 2 mainly composed of silver and an insulating layer 4 made of borosilicate glass.
(Linear expansion coefficient: 8.2 × 10 ⁻⁶ / ° C.), the second wiring layer 3 containing silver as a main component, and the above-described connection conductor 6 are all formed by a thick film method, and the material and paste of each layer The temperature conditions at the time of baking were all the same, and only the content of the tungsten oxide fine particles 7 present in the connection conductor 6 was reduced to 0.01.
The weight ratio was varied within the range of wt% to 9.00 wt%.

Table 1 shows the results of confirming the occurrence of cracks in the connection conductors 6 and measuring the conductive resistance of the connection conductors 6 for the samples Nos. 1 to 12.

[0036]

[Table 1]

According to Table 1, the sample No. in which the content of the tungsten oxide fine particles 7 is less than 0.10 wt%.
In Nos. 1 and 2, it was confirmed that the connection conductor 6 was cracked, and the conductive resistance could not be measured.

Samples No. 11 and No. 12 in which the content of the tungsten oxide fine particles 7 is larger than 7.00 wt% have a large conductive resistance of 3 mΩ or more, and the power is largely lost in this portion. .

On the other hand, in the samples No. 3 to No. 10 in which the content of the tungsten oxide fine particles 7 was set to 0.10 wt% to 7.00 wt%, there was no crack in the connection conductor 6 at all. Also, the conductive resistance is 0.94 mΩ or more.
It is relatively small at 2.87 mΩ, and power loss in this portion is small.

Therefore, according to the above-described experimental results, in order to keep the conductive resistance sufficiently low without causing cracks in the connection conductor 6 in the through-hole 5, the tungsten oxide contained in the connection conductor 6 should be used. It can be seen that the content of the fine particles 7 must be set at 0.1 wt% to 7.0 wt%.

[0041]

According to the multilayer wiring board of the present invention, the first wiring layer and the second wiring layer are sequentially laminated on the upper surface of the substrate with an insulating layer interposed therebetween, and the first wiring layer and the second wiring layer are stacked. In a multilayer wiring board in which a wiring layer is electrically connected by connection conductors in through holes provided in an insulating layer, the connection conductors contain 0.1 wt% to 7.0 w of tungsten oxide fine particles.
When the insulating layer and the connection conductor are formed by a conventionally known thick film method, the amount of shrinkage between the connection conductor and the insulation layer is reduced with cooling after baking the glass paste or the conductive paste. Even if a thermal stress caused by the difference is applied, the stress can be favorably alleviated and absorbed by the deformation of the tungsten oxide fine particles, and the first wiring layer and the second wiring layer can be satisfactorily formed without any cracks in the connection conductor. It is possible to make electrical connection in a proper state.

According to the multilayer wiring board of the present invention, the tungsten oxide fine particles are distributed more in the peripheral area than in the central area of the connecting conductor, so that the above-mentioned interface is provided near the interface between the two where the thermal stress is maximized. Of tungsten oxide particles are concentrated, so that stress can be absorbed and reduced more effectively.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer wiring board according to one embodiment of the present invention.

FIG. 2 is an enlarged view schematically showing a main part of FIG.

FIG. 3 is a sectional view of a conventional multilayer wiring board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... 1st wiring layer, 3 ... 2nd wiring layer, 4 ... insulating layer, 5 ... through-hole, 6 ...
Connection conductor, 7 ... Tungsten oxide fine particles

Continued on the front page F-term (reference) 4E351 AA07 BB01 BB24 BB26 BB31 BB49 CC11 CC22 DD04 DD05 DD06 DD16 DD34 DD52 DD58 EE02 GG03 GG08 5E317 AA24 BB04 BB12 BB13 BB14 BB16 CC22 CC25 CC53 CD32 GG05 A05A12 CC CC32 CC36 CC38 CC39 DD45 FF18 GG06 GG09 HH07

Claims (3)

[Claims] A first wiring layer and a second wiring layer are sequentially laminated on an upper surface of a substrate via an insulating layer between the first wiring layer and the second wiring layer.
In a multilayer wiring board in which a wiring layer and a second wiring layer are electrically connected by a connection conductor in a through hole provided in an insulating layer, 0.1 w of tungsten oxide fine particles are contained in the connection conductor.
A multilayer wiring board characterized by containing t% to 7.0 wt%. 2. The method according to claim 1, wherein said tungsten oxide fine particles have a particle size of 0.1.
2. The film according to claim 1, wherein the thickness is in the range of 0.05 to 5.0 .mu.m.
2. The multilayer wiring board according to item 1. 3. The multilayer wiring board according to claim 1, wherein the tungsten oxide fine particles are distributed more in a peripheral area than in a central area of the connection conductor.