JP2002084052A - Conductive member for filling up through hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive member which fills up a through hole without causing wear nor generating voids and has good conductivity, and to provide a wiring board using the member. SOLUTION: This conductive member for filling up through hole is prepared by mixing (b) a metal having a low melting point of <=300 deg.C and (c) metal powder in (a) a substrate composed of a thermoplastic resin or thermoplastic elastomer, and their mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive member for filling through holes and a circuit board using the same.

[0002]

2. Description of the Related Art A silver paste or a copper paste obtained by mixing silver powder or copper powder in a thermosetting resin has been known as the conductive member. However, silver paste is generally excellent in conductivity but inferior in migration resistance.
In the case of copper paste, there is a problem that copper is easily oxidized. A thermosetting paste using a copper and silver alloy powder having excellent oxidation resistance and migration resistance is known, but a thermosetting resin such as a phenol resin is used.
The paste contains a large amount of volatile solvents in order to impart appropriate fluidity (for example, Japanese Patent Application Laid-Open No. 62-164737,
Japanese Patent Application Laid-Open No. 1-165654). As a result, the cured paste after filling the inside of the through-hole and heat-curing causes a large film loss due to the evaporation of the solvent, and therefore, the mountability of components on the through-hole is inferior, and the evaporation of the solvent As a result, voids are likely to be generated, causing a decrease in the reliability of the through hole. In addition, the solder paste composed of a solder brazing material and a thermoplastic resin material as shown in JP-A-11-320176 and a flux component also contains a flux component although a thermosetting resin is not used, There is a problem that voids are easily generated with the volatilization of the flux component.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems.
Without film loss or voids in the through holes,
Moreover, it is an object of the present invention to provide a conductive member having good conductivity and a wiring board using the same.

[0004]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, the gist of the present invention is that (a) a thermoplastic resin or a thermoplastic elastomer and a mixture thereof are used as a substrate, (b) a low-melting-point metal having a melting point of 300 ° C. or less, and (c) a metal powder. Conductive member for filling through holes.

[0005] Preferred embodiments of the present invention include the following. (A) The thermoplastic resin or the thermoplastic elastomer and the mixture thereof are 20 to 80% by volume of the adhesive resin composition, and the proportion of the metal powder (c) in the metal component combining (b) and (c) is The above-mentioned conductive member for filling a through hole, wherein the content is in the range of 10 to 30% by volume. The low melting point metal of the component (b) is Pb / Sn, Pb / Sn /
Bi, Pb / Sn / Ag, Pb / Ag, Sn / Ag, S
The above-mentioned conductive member for filling a through hole, comprising a low melting point alloy selected from n / Bi, Sn / Cu, and Sn / Zn. The metal powder of the component (c) is composed of Cu, Ni, Al, Cr and an alloy powder thereof, and has an average particle size of 1 to 50 μm.
The conductive member for filling a through hole according to the above, wherein: (A) The above-mentioned conductive member for filling a through hole, wherein a part of a thermoplastic resin or a thermoplastic elastomer and a mixture thereof is acid-modified and contains a carboxyl group.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The conductive member for filling a through hole according to the present invention comprises: (a) a thermoplastic resin or a thermoplastic elastomer and a mixture thereof; (b) a low melting point metal having a melting point of 300 ° C. or less; , "Mixed material"). By using a specific combination of a thermoplastic resin or a thermoplastic elastomer and a mixture thereof and a metal component for imparting conductivity, other properties such as extremely high conductivity and adhesion can be imparted in a well-balanced manner. It has been found that, as the mixed material, (a) a thermoplastic resin or a thermoplastic elastomer and a mixture thereof can be used in a total amount of 20%.
The content is preferably in the range of ８０80% by volume, preferably 40-60% by volume. If the content of the resin component exceeds 80% by volume, conductivity tends to be hardly exhibited. If the content is less than 20% by volume, the fluidity is reduced, and the wettability necessary for adhesiveness and the filling property for through holes are inferior.

Further, in order to improve the adhesive strength between a thermoplastic resin or a thermoplastic elastomer and a mixture thereof and a low melting point metal and to firmly express the adhesiveness to an adherend, the thermoplastic resin or the thermoplastic elastomer is used. It is necessary to modify a part with an organic unsaturated carboxylic acid having 3 to 10 carbon atoms. As the organic unsaturated carboxylic acid, for example, acrylic acid, maleic acid, methacrylic acid, fumaric acid,
Itaconic acid and the like are preferred. The metal powder (c) acts as a dispersing aid for the low-melting metal, and the proportion of the metal powder (c) in the metal component is 10 to 30% by volume, preferably 15 to 25% by volume.
It is preferable to set it in the range of volume%. If it is less than 10% by volume, the dispersion state will be poor, and if it exceeds 30% by volume, the fluidity will be reduced, the embrittlement will be liable to occur, and the conductivity will be further reduced.

[0008] The thermoplastic resin or thermoplastic elastomer (a) used in the admixture includes olefin-based thermoplastic resins and thermoplastic elastomers.
Various types such as styrene type, PVC type, urethane type, ester type and amide type can be used, but a soft material is suitable for enhancing stress relaxation due to thermal stress.

Various kinds of low melting point metals having a melting point of 300 ° C. or less can be used. The melting point can be measured by the differential scanning calorimetry (DSC).
The measurement may be performed according to C), and there is a problem that a metal having a melting point exceeding 300 ° C. has poor moldability. Specifically, P
b / Sn, Pb / Sn / Bi, Pb / Sn / Ag, Pb
/ Ag, Sn / Ag, Sn / Bi, Sn / Cu, Sn /
A solder alloy selected from Zn-based can be suitably used.
The metal powder of the component (c) serves as a dispersing aid for the low-melting-point metal, and Cu, Ni, Al, Cr and alloy powders thereof can be suitably used, and the average particle size is 1 to 50 μm.
Are preferred. The average particle diameter is a number average particle diameter obtained by photographing a sample with a transmission electron microscope and obtaining the photograph. When the average particle size is less than 1 μm, handling during mixing is difficult, and when the average particle size exceeds 50 μm, the dispersibility tends to decrease.

The conductive member for filling a through hole according to the present invention can be obtained by kneading the mixture at a predetermined temperature with a kneader such as a kneader or a twin-screw extruder using the above-mentioned components of the mixture. The kneaded product is used after being shaped into a form that can be filled into a dispenser having a heating mechanism such as a pellet or a rod. In kneading, (c) a temperature at which the low-melting metal is in a semi-molten state is preferable, and an appropriate metal composition is selected according to the melting temperature of the thermoplastic resin or the thermoplastic elastomer serving as a matrix. It is necessary to appropriately select the addition ratio of the copper powder, the nickel powder, and the like to be used.

As a substrate material of the through-hole circuit board used in the present invention, a known material can be used. For example, paper substrate, glass cloth or glass non-woven fabric
Urea resin, melamine resin, phenol resin, epoxy resin, fluorine resin, polyether resin,
A rigid wiring board impregnated with a thermosetting resin such as a polyimide resin may be used. Alternatively, there is a flexible wiring board in which wiring is provided on a film made of a polyester resin, a polyamide resin, a polyimide resin, or the like. In addition, a substrate using a metal plate as a core material, a composite substrate, a ceramic substrate, or the like can also be used.

As a method for drilling through holes used in the present invention, a known method can be used. For example, there are a punching method and a drilling method. There is no particular limitation on the inner diameter of the through hole, but the through hole has a diameter that allows filling of the conductive member, and is generally in the range of 0.2 mm to 2 mm. Further, the through hole may be closed in the middle of the substrate instead of the through hole as necessary. As a method of filling the conductive member into the through hole, the conductive member can be injected by a dispenser method having a heating cylinder.

As described above, the conductive member for filling a through hole according to the present invention has a very high conductivity because the thermoplastic resin or the thermoplastic elastomer and the mixture thereof contain the low melting point metal. On the other hand,
Since a part of the resin is acid-modified, it has a strong adhesive strength, and since it does not contain a solvent, it is possible to provide a wiring board which is free from film loss and voids in through holes.

[0014]

The present invention will be specifically described below with reference to examples and comparative examples. (Embodiment) The conductive member used in the embodiment of the present invention is a thermoplastic elastomer such as "Santoprene 8211-3".
5 "/ AES Japan, acid-modified polyolefin (" Adtex ER320P "manufactured by Nippon Polyolefin Co., Ltd.) as a thermoplastic resin, and a lead-free solder (Sn-4Cu-2Ni melting point solid phase wire 22) as a low melting metal.
5 ° C-liquidus 480 ° C), average particle size 10 as metal powder
μm copper powder was used. Each raw material powder is physically mixed in advance (40% by volume of thermoplastic elastomer, 10% by volume of acid-modified polyolefin, 45% by volume of low melting point metal, 5% by weight of metal powder).
% By volume) and a kneader (Moriyama Seisakusho, 2-axis pressurized type) to obtain a melt-kneaded product. The volume resistivity of the kneaded product was 3 × 10 ⁻⁴ Ω · cm.

The kneading conditions are as follows. Cylinder temperature: 200 ° C Screw rotation speed: 35r. p. m.

Next, a through-hole having a drilled hole with a diameter of 0.6 mm is formed on a copper-clad laminated substrate in which a copper foil having a thickness of 35 μm is laminated on both sides of a glass substrate-epoxy resin plate having a thickness of 0.4 mm. A substrate was prepared. Plunger filling machine having a heating cylinder in this through hole (200 ° C)
After filling and cooling the kneaded material by using the method, as a result of observing the cross section of the obtained filled through hole with a microscope (100 times magnification),
No film loss or void was observed. (Comparative example)

A commercially available conductive member (conductive filler: Ag)
/ 90% by weight, binder: one-component curable epoxy resin) was used to fill the through holes of the laminated substrate.
(Heat curing at 80 ° C. for 30 minutes and 180 ° C. for 60 minutes) As a result of observing the cross section of the filled through hole obtained in the same manner as in the example with a microscope (magnification: 100 times), thinning and voids were observed inside the cured product. Was done.

[0018]

As described above, the conductive member for filling through-holes of the present invention has a very high conductive property because the thermoplastic resin or the thermoplastic elastomer and the mixture thereof contain a low melting point metal. Having. Furthermore, a wiring board having a strong adhesive strength by partially denaturing a resin and not containing a solvent can be provided without a decrease in film thickness or generation of voids in through holes.

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Claims (6)

[Claims] 1. A mixture comprising (a) a thermoplastic resin or a thermoplastic elastomer and a mixture thereof as a substrate, (b) a low-melting metal having a melting point of 300 ° C. or less, and (c) a metal powder. A conductive member for filling through holes. 2. The method according to claim 1, wherein (a) a thermoplastic resin or a thermoplastic elastomer and a mixture thereof are used for the conductive member.
2. The conductive material for filling a through-hole according to claim 1, wherein the proportion of the metal powder (c) in the metal component comprising 80% by volume and (b) and (c) is in the range of 10 to 30% by volume. Sex members. 3. The low melting point metal of component (b) is Pb / S
n, Pb / Sn / Bi, Pb / Sn / Ag, Pb / A
g, Sn / Ag, Sn / Bi, Sn / Cu, Sn / Zn
3. The conductive member for filling a through hole according to claim 1, wherein the conductive member is made of a low melting point alloy selected from the group consisting of: 4. The metal powder of component (d) is Cu, Ni, A
2. The powder of claim 1, wherein said powder is made of l, Cr or an alloy powder thereof, and has an average particle diameter in the range of 1 to 50 μm.
4. The conductive member for filling a through hole according to any one of items 3 to 3. 5. The through-hole filling according to claim 1, wherein (a) a part of the thermoplastic resin or the thermoplastic elastomer and a mixture thereof is modified with an acid and contains a carboxyl group. For conductive members. 6. A circuit board using the conductive member for filling a through hole according to claim 1, wherein a through hole is formed in an insulating base material, and the through hole is filled with the conductive member. A circuit board characterized by the above-mentioned.