JP2003317541A - Conductive paste and wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste of which the conductor filling operability in respective through holes is excellent and also to provide a wiring board of which the respective through conductors have a respective low resistance even the content of a conductive powder is high. <P>SOLUTION: This wiring board is produced through the use of a conductive paste containing triallyl isocyanurate of 5 to 20 mass%, triallyl isocyanurate prepolymer of 0.25 to 8 mass%, polymer dispersing agent 2 of 0.05 to 2 mass%, metal powder 3 of 40 to 75 mass%, and a solder ball 4 of 20 to 55 mass%. The average particle size of the solder ball 4 is 30 to 60% of that of the metal powder 3. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of insulating resin layers, a wiring conductor formed on the surface of the insulating layer and between the insulating layers, and a through conductor formed by electrically connecting upper and lower wiring conductors. The present invention relates to a good conductor paste for a penetrating conductor of a provided wiring board and a wiring board using the same.

[0002]

2. Description of the Related Art Conventionally, as a wiring board used for mounting electronic parts such as semiconductor elements and resistors, a heat-resistant fiber base material such as a glass fiber base material and an insulating resin layer made of a thermosetting resin and a copper foil. A wiring board is formed by alternately laminating a plurality of wiring conductors made of, for example, etc., and electrically connecting the wiring conductors located above and below with the insulating resin layer in between by a through conductor formed in the insulating resin layer. Are known.

In such a wiring board, a through hole is formed by a laser in an insulating sheet for an insulating resin layer formed by impregnating a heat-resistant fiber base material with a thermosetting resin precursor, and then a conductive material is formed in the through hole. A conductor paste for through conductors consisting of powder and thermosetting resin precursor is embedded by screen printing (press-fitting), while a copper foil is adhered to the surface of a transfer sheet made of heat-resistant resin and formed into a predetermined pattern. The wiring conductor is formed on the transfer sheet by etching, and thereafter, the transfer sheet having the wiring conductor formed thereon is pressed onto the surface of the insulating sheet filled with the conductive paste to transfer the wiring conductor to the insulating sheet. At the same time, the wiring conductor and the conductor paste are connected, and then the transfer sheet is peeled off from the insulating sheet, and then a plurality of layers of the insulating sheet in which the wiring conductor is embedded are laminated and the insulating sheet is separated. The thermosetting resin precursor in the preparative and the conductor paste is fabricated by thermally curing. At this time, the conductor paste is densely filled in the through holes by embedding the conductor paste in a shape that is raised from the surface of the insulating sheet and pressing the transfer sheet on which the wiring conductor is formed from above. .

As such a conductor paste, for example, 5 to 20 mass% of triallyl isocyanurate and 0.25 to 8 mass% of triallyl isocyanurate prepolymer are used.
Japanese Patent Application Laid-Open No. 2001-176328 proposes a conductor paste containing 80 to 94% by mass of conductive powder. The conductor paste having the above composition is obtained by curing the thermosetting resin precursor triallyl isocyanurate to bond the conductive powders of the metal powder and the solder powder to each other to form a through conductor. The through conductors exhibit conductivity by connecting the metal powders with solder powders.

[0005]

However, the above-described conductor paste has poor wettability between the conductive powder and triallyl isocyanurate, and when stored for a long time, the conductive powder and triallyl isocyanurate separate. And
There has been a problem that the viscosity of the conductor paste becomes extremely high, which makes it difficult to fill the conductor paste.

Further, in the above-mentioned conductor paste, the gap between the conductive powders of the metal powder and the solder powder is large, and therefore, when the content ratio of the conductive powders becomes high, the triallyl isocyanurate and the triaryl isocyanurate and the triaryl isocyanurate are formed between the conductive powders. There is a problem that it is difficult to sufficiently fill with the allyl isocyanurate prepolymer, the viscosity of the conductor paste becomes high, and it becomes difficult to fill the through holes well.

Further, in the wiring board using the above-mentioned conductor paste, since the conductive powder and the triallyl isocyanurate have poor wettability after the conductor paste is embedded in the through holes, the conductive powder and the triallyl isocyanate are poor. The conductive powder is not densely packed because it is separated from the nurate, the gap between the conductive powders in the through conductor becomes large, and it is difficult to reliably arrange the solder powder between the metal powders. There is a problem that it is difficult to satisfactorily connect the metal powders to each other with the solder powder, and the conduction resistance of the through conductor tends to increase.

The present invention has been completed in view of the problems of the prior art, and an object thereof is to fill the through holes even if the content of the conductive powder composed of the metal powder and the solder powder becomes high. An object of the present invention is to provide a conductor paste having excellent properties and a wiring board having a low conduction resistance of a through conductor.

[0009]

The conductor paste of the present invention comprises 5 to 20% by mass of triallyl isocyanurate and 0.25 to 8% by mass of triallyl isocyanurate prepolymer.
And 0.05 to 2% by mass of a polymer dispersant, 40 to 75% by mass of metal powder, and 20 to 55% by mass of solder powder. This solder powder has an average particle size of that of the metal powder. Particle size 30 ~
It is characterized by being 60%.

In the wiring board of the present invention, a plurality of insulating resin layers in which a heat-resistant fiber base material is impregnated with a thermosetting resin and wiring conductors made of a metal foil are alternately laminated, and the insulating resin layers are sandwiched. It is characterized in that the upper and lower wiring conductors are electrically connected to each other by a through conductor formed by thermosetting the above conductor paste filled in a through hole provided in an insulating resin layer.

According to the conductor paste of the present invention, since the conductor paste contains the polymer dispersant in an amount of 0.05 to 2% by weight, the polymer dispersant is adsorbed on the metal powder and the solder powder, and these are mixed. The conductor paste can be satisfactorily dispersed in allyl isocyanurate, and as a result, a conductor paste can be obtained in which the viscosity does not change even after long-term use and the filling property does not deteriorate.

Further, according to the conductor paste of the present invention, since the average particle size of the solder powder is set to 30 to 60% of the average particle size of the metal powder, when the content ratio of the metal powder and the solder powder becomes high. In this case, the solder powder having a small particle size surely enters the gaps between the metal powders to make the gaps between the metal powders small, and a small amount of triallyl isocyanurate and triallyl isocyanurate prepolymer is sufficient for the small gaps. It is possible to obtain a conductor paste which has a low viscosity and can be well filled in the through holes.

Further, according to the wiring board of the present invention, since the through conductor is formed by thermosetting the above-mentioned conductor paste filled in the through hole, the solder powder having a small particle size is formed in the gap between the metal powders. The conductive powder such as the metal powder or the solder powder is tightly filled and the metal powder is satisfactorily connected by the solder powder entering the gap between the metal powders. As a result, the conduction resistance of the through conductor is reduced. It can be a low wiring board.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a conductor paste of the present invention and a wiring board using the same will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a dispersed state of metal powder and solder powder of the conductor paste of the present invention. In this figure, 1 is a mixture of triallyl isocyanurate and triallyl isocyanurate prepolymer, 2 is a polymer dispersant, 3 is a metal powder, 4 is a solder powder, and these constitute the conductor paste 5 of the present invention. To be done. Then, the conductor paste 5 is embedded and filled in, for example, a through hole provided in an insulating sheet for an insulating resin layer, and is thermally cured to form a through conductor in the insulating resin layer.

The conductor paste of the present invention contains 5 to 20% by mass of triallyl isocyanurate, 0.25 to 8% by mass of triallyl isocyanurate prepolymer, and 0.05 of a polymer dispersant.
~ 2% by mass, metal powder 40 to 75% by mass, solder powder 20 to
And 55% by mass.

Triallyl isocyanurate has a function of fixing the metal powder 3 and the solder powder 4 by filling the space between the metal powder 3 and the solder powder 4 and thermosetting, and its content is 5 to 20 mass%. preferable. If the content is less than 5% by mass, the viscosity of the conductor paste 5 is too high and the embedding property of the conductor paste 5 in the through holes is lowered, and the resistance value of the through conductor tends to increase. If the amount is large, the viscosity of the conductor paste 5 becomes too low, and the conductor paste 5 tends to bleed onto the surface of the insulating resin layer. Therefore, the content of triallyl isocyanurate is preferably 5 to 20% by mass.

Although triallyl isocyanurate is a monomer having a molecular weight of 250, the viscosity of the conductor paste 5 can be increased by adding 0.25 to 8% by mass of triallyl isocyanurate prepolymer obtained by polymerizing triallyl isocyanurate. Can be adjusted, the conductor paste 5
Can be suppressed from seeping out to the surface of the insulating resin layer.

When the content of triallyl isocyanurate prepolymer is less than 0.25% by mass, it tends to be difficult to adjust the viscosity of the conductor paste 5, and when it is more than 8% by mass, triallyl isocyanurate prepolymer is contained. Becomes difficult to completely dissolve, and the conductor paste 5
However, the homogeneity of the material tends to deteriorate, and the workability of embedding tends to decrease. Therefore, the content of the triallyl isocyanurate prepolymer is preferably 0.25 to 8% by mass. In order to obtain good solubility of the triallyl isocyanurate prepolymer in the conductor paste 5 and to adjust the initial viscosity of the conductor paste 5 well, the weight average molecular weight of the triallyl isocyanurate prepolymer is 1500. ~ 7000
It is preferably 0.

Further, since the conductor paste 5 of the present invention contains the polymer dispersant 2 in an amount of 0.05 to 2% by weight, FIG.
As shown in, the polymer dispersant 2 can be adsorbed on the metal powder 3 and the solder powder 4 to disperse the metal powder 3 and the solder powder 4 in triallyl isocyanurate well, Also, it is possible to obtain the conductor paste 5 in which the viscosity does not change and the filling property does not decrease.

Examples of such a polymer dispersant 2 include anionic polymer dispersants such as formalin condensate of sodium naphthalene sulfonate and sodium polysulfonate, ethylene oxide adducts of nonylphenol formalin condensate, and propylene oxide of polyethylene polyamine. A nonionic polymer dispersant such as an ethylene oxide adduct can be used.

The content of the polymer dispersant 2 is 0.05 to 2
Weight percent is preferred. If the content is less than 0.05% by weight, the viscosity will increase when used for a long period of time, resulting in poor embedding. The contact resistance of the powder 3 and the solder powder 4 tends to increase. Therefore,
The content of the polymer dispersant 2 is preferably 0.05 to 2% by weight.

The conductor paste 5 of the present invention is formed by filling the through-holes and thermosetting to melt the surface of the solder powder 3 and connect the metal powders 3 with the solder powder 4. It becomes a through conductor. The metal powder 3 is preferably at least one metal selected from gold, silver, palladium, copper, nickel, tin, and lead. Specifically, the above-mentioned pure metals and their alloys or A mixture, or a core of a metal selected from the above and coated with another metal can be used. In particular, copper is preferable in terms of suppressing migration and being inexpensive, and in consideration of chemical stability, copper powder coated with silver is most suitable.
Further, as the solder powder 4, tin, lead, silver, indium,
An alloy of two or more kinds of metals selected from antimony, bismuth and the like is preferable.

The content of the metal powder 3 is preferably 40 to 75% by mass. If the content of the conductive powder is less than 40% by mass, the resistance value tends to increase because the number of contact points between the metal powders 3 decreases in the through conductor formed by thermosetting the conductor paste 5. If the amount is more than 75% by mass, it tends to be difficult to adjust the viscosity of the conductor paste 5. Therefore, the content of the metal powder 3 is preferably 40 to 75% by mass. The content of the solder powder 4 is preferably 20 to 55 mass%. If the content of the solder powder 4 is lower than 20%, it is difficult to satisfactorily connect the metal powders 3 with the solder powder 4 because the solder powder 4 is too small in the through conductor formed by thermosetting the conductor paste 5. And the conduction resistance tends to increase, and when it is less than 55% by mass, in the through conductor formed by thermosetting the conductor paste 5,
The solder powder 4 is applied with a temperature equal to or higher than the melting point of the solder powder 4.
When is melted, the shape of the through conductor tends to change. Therefore, the content of the solder powder 4 is preferably 20 to 54 mass%.

Furthermore, in the conductor paste 5 of the present invention, the average particle size of the solder powder 4 is 30 to 60% of the average particle size of the metal powder 3, which is important. The average particle size of the solder powder 4 is 30% of the average particle size of the metal powder 3.
If it is smaller, the amount of fine powder of the solder powder 4 increases, and the fine powder adheres to the surface of the metal powder 3, and the viscosity of the conductor paste 5 increases, which tends to prevent good embedding. It becomes difficult for the solder powder 4 to reliably enter in between, and the space between the metal powder 3 and the solder powder 4 becomes large, and the space is sufficiently filled with a small amount of triallyl isocyanurate and triallyl isocyanurate prepolymer. However, the viscosity of the conductor paste 5 tends to be high. Also, in the through conductor formed by thermosetting the conductor paste 5, the gap between the metal powders 3 becomes large, the metal powders 3 and the solder powders 4 are not densely filled, and the solder powders 4 are placed between the metal powders 3. It becomes difficult to dispose the metal powder 3 reliably, and as a result, the metal powders 3 cannot be sufficiently connected with the solder powders 4, and the conduction resistance of the through conductor tends to increase. Therefore, it is important to set the average particle size of the solder powder 4 to 30 to 60% of the average particle size of the metal powder 3.

The average particle size of the metal powder 3 is 4 to 10 μm.
Is preferred. If the average particle size is smaller than 4 μm, the viscosity of the conductor paste 5 becomes high, and it tends to be difficult to embed, and if it exceeds 10 μm, the metal powder 3 cannot be highly filled and the conduction resistance tends to be high. Therefore, the average particle size of the metal powder 3 is preferably 4 to 10 μm.

In order to accelerate the curing of triallyl isocyanurate, 0.25 to 3 mass% of an organic peroxide such as hydroperoxide, dialkyl peroxide, diallyl peroxide may be added as a radical polymerization initiator. good.

Thus, according to the conductor paste 5 of the present invention, since the polymer dispersant 2 is contained in an amount of 0.05 to 2% by weight, the polymer dispersant 2 is adsorbed on the metal powder 3 and the solder powder 4. The metal powder 3 and the solder powder 4 can be satisfactorily dispersed in triallyl isocyanurate, and as a result, there is no change in viscosity even when used for a long period of time, and the conductor paste 5 does not deteriorate in filling property. be able to.

According to the conductor paste of the present invention, the conductive powder is composed of the metal powder 3 and the solder powder 4, and the average particle diameter of the solder powder 4 is 30 to 30 times the average particle diameter of the metal powder 3.
Since the content is 60%, the viscosity of the conductive paste 5 can be lowered even if the content of the conductive powder is high, and as a result, the conductive paste 5 can be filled well into the through holes.

The method for preparing the conductor paste 5 of the present invention is, for example, 8.1% by mass of triallyl isocyanurate, 0.9% by mass of triallyl isocyanurate prepolymer, and ethylene as a nonylphenol formalin condensate as the polymer dispersant 2. 1 mass% of oxide adduct, 45 mass% of metal powder 2 having an average particle size of 10 μm, average particle size of 5 μm
It is possible to adjust the viscosity to a predetermined value by mixing 45 mass% of the solder powder 3 of m and kneading with a stirring defoaming machine. Further, in order to improve the filling property into the through holes, it is preferable to adjust the viscosity of the conductor paste to 20 to 200 Pa · s at a shear rate of 100 s ⁻¹ .

Next, a wiring board using the above-mentioned conductor paste 5 will be described in detail with reference to FIG. FIG. 2 is a sectional view showing an example of an embodiment of a wiring board using the conductor paste 5 of the present invention. In this figure, 6 is an insulating resin layer, 7 is a wiring conductor, 8 is a through hole, and 9 is a through hole. It is a through conductor.
Note that FIG. 2 shows a wiring board formed by laminating four insulating resin layers 6.

The insulating resin layer 6 has a thickness of 50 to 150 μm.
It has the function of supporting the wiring conductors 7 and maintaining the insulation between the wiring conductors 7 positioned above and below, and the thermosetting property of the modified polyphenylene ether resin or triallyl isocyanurate to the heat resistant fiber such as glass cloth. It is made by impregnating a resin. If the thickness of the insulating resin layer 6 is less than 50 μm, the rigidity of the wiring board tends to decrease and the wiring board tends to bend, and if it exceeds 150 μm, the thickness of the insulating resin layer 6 becomes unnecessarily thick and wiring It tends to be difficult to reduce the weight of the substrate. Therefore, the insulating resin layer 6 has a thickness
The thickness is preferably 50 to 150 μm.

A wiring conductor 7 is embedded in the surface of each insulating resin layer 6. The wiring conductor 7 has a function as a part of a conductive path that electrically connects each electrode of an electronic component (not shown) mounted on the wiring board to an external electric circuit board (not shown), and has a width. Is about 20-200 μm, thickness is 5-50 μm
To some extent, it is made of a metal foil of copper, aluminum, nickel, silver, gold or the like, and is preferably made of a copper foil from the viewpoint of workability and low cost. If the width of the wiring conductor 7 is less than 20 μm, the wiring conductor 7 tends to be deformed or broken, and if it exceeds 200 μm, high-density wiring cannot be formed. In addition, the thickness of the wiring conductor 7 is 5 μm
If it is less than 50 μm, the strength of the wiring conductor 7 tends to decrease, and deformation or disconnection tends to occur. If it exceeds 50 μm, it tends to be difficult to embed it in the insulating resin layer 6. Therefore, the wiring conductor 7 preferably has a width of 20 to 200 μm and a thickness of 5 to 50 μm.

Further, each insulating resin layer 6 is provided with a plurality of through conductors 9 from the upper surface to the lower surface thereof. These through conductors 9 have a function of electrically connecting the wiring conductors 7 located above and below the insulating resin layer 6, and the through holes 8 provided in the insulating resin layer 6 are provided with triallyl isocyanurate in an amount of 5 to 5%. 20 mass%, triallyl isocyanurate prepolymer 0.25-8 mass%, polymer dispersant 2 0.05-2 mass%, metal powder 3 40-75 mass%, solder powder 4 20
˜55% by mass, and is formed by embedding and thermally curing the conductor paste 5 of the present invention in which the average particle size of the solder powder 4 is 30 to 60% of the average particle size of the metal powder 3. . The through-hole 8 has a diameter of about 30 to 200 μm, and if the diameter is less than 30 μm, its processing tends to be difficult, and if it exceeds 200 μm, high-density wiring cannot be formed. Therefore, the through hole 8 has a diameter
The thickness is preferably 30 to 200 μm.

According to the wiring board of the present invention, since the through-hole conductor 9 is formed by filling the through-hole 8 with the above-mentioned conductor paste 5 and thermosetting, the particle size in the gap between the metal powders 3 is small. The solder powder 4 surely enters, the conductive powder composed of the metal powder 3 and the solder powder 4 is densely filled, and the solder powder 4 entering the gap between the metal powders 3 connects the metal powders 3 well. As a result, it is possible to obtain a wiring board in which the conduction resistance of the through conductor 9 is low.

Such a wiring board is manufactured by the method described below. First, for example, a thermosetting resin composition comprising 100 parts by weight of a modified polyphenylene resin, 5 parts by weight of triallyl isocyanurate, and 20 parts by weight of a styrene-ethylene-butylene-styrene tetrablock polymer on a heat-resistant fiber such as glass cloth. An insulating sheet for the insulating resin layer 6 is manufactured by impregnating the material, and then a diameter of the insulating sheet for the insulating resin layer 6 is applied at a predetermined position by a well-known method such as a carbon dioxide laser or a YAG laser. Is 30 ~
A hole for the through hole 8 of about 200 μm is formed. Then, the conductor paste 5 of the present invention described above is applied to the through holes 8 by a screen printing method (press-fitting) according to the present invention.
Fill with. Thereafter, a separately prepared transfer sheet made of a heat-resistant resin such as polyethylene terephthalate (PET) resin, on the surface of which a wiring conductor 7 made of copper foil is formed in a predetermined pattern, is used as an insulating sheet for the insulating resin layer 6. , The conductor paste 5 filled in the holes for the through holes 8 and the wiring conductor 7 are aligned and overlapped so as to be connected, and these are pressed with a hot press machine at a temperature of 100 to 150 ° C. for several minutes. Thus, the transfer sheet is pressed against the insulating sheet for the insulating resin layer 4, and the wiring conductor 7 is transferred and embedded in the insulating sheet for the insulating resin layer 6. After that, the transfer sheet is peeled from the insulating sheet for the insulating resin layer 6, and a plurality of insulating sheets for the insulating resin layer 6 from which the transfer sheet is peeled are stacked on top of each other, and a heat press machine is used to heat the sheet at 150 to 200 ° C. A wiring board is obtained by heat-pressing the insulating sheet and the conductor paste 5 at a temperature for several hours to cure them.

A part of the wiring conductor 7 formed on the surface of one outermost layer of the insulating resin layer 6 is an electronic component (not shown).
Part of the wiring conductor 7 formed on the surface of the other outermost layer of the insulating resin layer 6 is formed by forming a mounting electrode 11a for connecting an electronic component, which is joined to each of the electrodes via a conductor bump 10a. External mounting connection electrodes 11b are formed on each electrode of a circuit board (not shown) via conductor bumps 10b.

On the surfaces of the mounting electrodes 11a and 11b,
The conductive bumps 10a and 10b are prevented from being oxidized and corroded.
In order to make a good connection with, a plating layer of nickel-gold or the like having good wettability with solder and excellent in corrosion resistance is deposited.

If necessary, the outermost insulating resin layer 4 and the mounting electrodes 11a and 11b may be mounted on the mounting electrodes 11a and 11b.
A solder resistant resin layer 12 having an opening for exposing the central portion of b is applied. The solder-resistant resin layer 12 has a thickness of 10 to 50.
It is about μm and is made of an insulating material in which a mixture of a photosensitive resin such as an acrylic modified epoxy resin and a photoinitiator contains 30 to 70% by mass of an inorganic powder filler such as silica or talc, which are adjacent to each other. Mounting electrodes 11a, 11b
The conductor bumps 10a and 10b are prevented from electrically short-circuiting each other, and have a function of improving the bonding strength between the mounting electrodes 11a and 11b and the insulating resin layer 6.

Such a solder-resistant resin layer 12 is formed by applying an uncured resin film composed of a photosensitive resin, a photoinitiator and an inorganic powder filler onto the surface of the outermost insulating resin layer 6, or by thermosetting. Applying an uncured resin varnish consisting of a resin and an inorganic powder filler to the surface of the outermost insulating resin layer 6 and drying, and then forming an opening by exposure and development, and UV-curing and heat-curing this. Is formed by.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the present invention. For example, in the above-mentioned embodiments, four insulating layers are used. Although the case where the layers are stacked is shown as an example, the number of layers may be five or more.

[0041]

EXAMPLES First, as shown in Table 1, triallyl isocyanurate (TAIC), triallyl isocyanurate prepolymer (TAICPP), a polymer dispersant, and
A metal paste and a solder powder were prepared, 1 mass% of diallyl peroxide was added thereto, and the mixture was kneaded by a stirring defoaming machine to prepare a conductor paste. Further, the viscosity of the conductor paste at a shear rate of 100 s ^-1 was measured using a cone type viscometer.

Next, 100 parts by weight of modified polyphenylene resin, 5 parts by weight of triallyl isocyanurate, and styrene-ethylene-butylene- were added to heat resistant fibers such as glass cloth.
By impregnating a thermosetting resin composition consisting of 20 parts by weight of styrene tetrablock polymer, the thickness is 100 μm.
4 insulating sheets were prepared, and through holes each having a diameter of 100 μm were formed at the same position of each insulating sheet by using a conventionally known method such as a carbon dioxide gas laser or a YAG laser. Then, the through-holes were filled with the conductor paste previously prepared by employing a conventionally known screen printing method by the screen printing method (press-fitting). After that, a copper foil with a diameter of 150 μm and a thickness of 15 μm was prepared separately.
A transfer sheet made of a heat-resistant resin such as polyethylene terephthalate (PET) resin, in which a circular wiring conductor is formed at a position corresponding to the through hole, is connected to the insulating sheet by the conductor paste and the wiring conductor. The sheets were aligned and superposed, and these were pressed at a temperature of 125 ° C. for several minutes using a heat press machine to press the transfer sheet into pressure contact with the insulating sheet and transfer-embed the wiring conductor in the insulating sheet.
Then, the transfer sheet was peeled off from the insulating sheet, and the insulating sheets from which the transfer sheet was peeled off were stacked on top of each other, and heat-pressed at a temperature of 200 ° C. for 3 hours using a heat press machine, so that the insulating sheet was thermoset. A wiring board was obtained in which the through conductor, which was obtained by thermosetting the conductor paste, penetrated the four insulating resin layers with the circular wiring conductor sandwiched between the respective layers. Next, the conduction resistance between both ends of the through conductor penetrating the four insulating layers was measured by a visual inspection and an electric tester. The results are shown in Table 1.

[0043]

[Table 1]

From Table 1, it is shown that triallyl isocyanurate (TAIC) is less than 5% by mass and triallyl isocyanurate prepolymer (TAICPP) is 0.25% by mass.
If it is less (Sample No. 1), the viscosity of the conductor paste becomes too high, resulting in poor embedding, and TAIC is 20% by mass.
More, TAICPP more than 2% by mass (Sample No.
5) and the viscosity of the conductor paste became too low to be embedded properly. On the other hand, TAIC is 5
.About.20% by mass and TAICPP of 0.25 to 2% by mass (Sample Nos. 2 to 4), the viscosity of the paste was 20 to 150 Pa.s, and good embedding was possible. Also, if the polymer dispersant is less than 0.05% by weight (Sample No. 6), the viscosity of the conductor paste after storage for 24 hours will rise sharply and it will not be possible to embed it. Therefore, the conductive powder was scattered during the transfer, and the insulation between the through conductors was deteriorated. On the other hand, the polymer dispersant is more than 2% by weight (Sample N
o.9) and the polymer dispersant did not dissolve well in triallyl isocyanurate and separated, resulting in poor appearance. On the other hand, the polymer dispersant is 0.05 to 2% by weight (Sample No.
7 and 8), there was no change in the viscosity of the conductor paste, good embedding was possible, and the conductor resistance of the through conductor was also low.

Further, when the average particle diameter of the solder powder is smaller than 30% of the average particle diameter of the metal powder (Sample No. 10), the solder powder is too small and the gap of the metal powder can be surely filled. Instead, the conduction resistance of the through conductor increased. On the other hand, if it is more than 60% (Sample No. 14), the solder powder is too large and the gap between the metal powders is widened, and it is not possible to satisfactorily fill the metal powder with a high conduction resistance. On the other hand, if the average particle size of the solder powder is 30 to 60% of the average particle size of the metal powder (Sample No. 11 to 13), the solder powder with a small particle size will surely enter the gap between the metal powders. As a result, the gap between the conductive powders becomes small.
It can be sufficiently filled with IC and TAICPP, has a low viscosity, and can be well filled into the through holes. Also, the content of metal powder is more than 74% by mass, and the content of solder powder is 20% by mass.
When the amount is smaller (Sample No. 15), the solder powder is too small, so that it is difficult to satisfactorily connect the metal powders with each other by the solder powder, and the conduction resistance is increased. On the other hand, the metal powder content is
When the content of solder powder is less than 40 mass% and the content of solder powder is more than 55 mass% (Sample No. 19), the shape of the through conductor changes when the solder powder 4 melts due to the temperature above the melting point of the solder powder 4 being applied. It was easy to do and the conduction resistance was high. On the other hand, the metal powder content is 40-75 mass%, the solder powder content is 20-
If it is 55% by mass (Sample No. 16 to 18), the solder powder with a small particle size will surely enter the gaps between the metal powders and the conductive powder will be densely packed, and the solder powders that have entered the gaps between the metal powders. Thus, the metal powders were satisfactorily connected to each other, and the conduction resistance of the through conductor was lowered.

[0046]

According to the conductor paste of the present invention, since the conductor paste contains 0.05 to 2% by weight of the polymer dispersant, the polymer dispersant is adsorbed on the metal powder and the solder powder, Can be satisfactorily dispersed in triallyl isocyanurate, and as a result, a conductor paste can be obtained in which the viscosity does not change even after long-term use and the filling property does not deteriorate.

Further, according to the conductor paste of the present invention, since the average particle size of the solder powder is set to 30 to 60% of the average particle size of the metal powder, when the content ratio of the metal powder and the solder powder becomes high. In this case, the solder powder having a small particle size surely enters the gaps between the metal powders to make the gaps between the metal powders small, and a small amount of triallyl isocyanurate and triallyl isocyanurate prepolymer is sufficient for the small gaps. It is possible to obtain a conductor paste which has a low viscosity and can be well filled in the through holes.

Further, according to the wiring board of the present invention, since the through conductor is formed by thermosetting the above-mentioned conductor paste filled in the through hole, the solder powder having a small particle size is formed in the gap between the metal powders. The conductive powder such as the metal powder or the solder powder is tightly filled and the metal powder is satisfactorily connected by the solder powder entering the gap between the metal powders. As a result, the conduction resistance of the through conductor is reduced. It can be a low wiring board.

[Brief description of drawings]

FIG. 1 is a schematic view showing a dispersed state of a metal powder and a solder powder of a conductor paste of the present invention.

FIG. 2 is a cross-sectional view showing an example of an embodiment of a wiring board using the conductor paste of the present invention.

[Explanation of symbols]

1 ··· Mixture of triallyl isocyanurate and triallyl isocyanurate prepolymer 2 ·· Polymer dispersant 3 ·· Metal powder 4 ·· Solder powder 5 ... Conductor paste 6 ... Insulating resin layer 7 ... Wiring conductor 8 ... Through hole 9 ... Through conductor

Claims (2)

[Claims] 1. A triallyl isocyanurate prepolymer of 5 to 20 mass% and a triallyl isocyanurate prepolymer of 0.
25 to 8% by mass and a polymer dispersant 0.05 to 2% by mass
40 to 75% by mass of metal powder and 20 to 55 of solder powder
%, And the solder powder has an average particle diameter of 30 to 60% of the average particle diameter of the metal powder. 2. A plurality of insulating resin layers in which a heat-resistant fiber base material is impregnated with a thermosetting resin and wiring conductors made of a metal foil are alternately laminated, and the wirings are vertically arranged with the insulating resin layer interposed therebetween. A wiring board, characterized in that the conductors are electrically connected by a through conductor formed by thermosetting the conductor paste according to claim 1 filled in a through hole provided in the insulating resin layer.