Method of making printed wiring board and method of making printed circuit board unit
The first support body is pressed against the second support body in response to the softening of the adhesive sheet. The fillers are allowed to reliably contact with one another between the first electrically-conductive land and the second electrically-conductive land. The fillers melt after the adhesive sheet has been softened. The intermetallic compounds are formed between the fillers and the electrically-conductive lands and between the fillers. Electrical connection is in this manner established between the first electrically-conductive land and the second electrically-conductive land. The matrix material and the adhesive sheet are then cured. The first support body and the second support body are firmly bonded to each other.
1. A method of making a printed wiring board, comprising:
setting an adhesive sheet made of a thermosetting resin between a first substrate and a second substrate so that a first electrically-conductive land provided on the first substrate is opposed to a second electrically-conductive land provided on the second substrate through an opening formed in the adhesive sheet;
filling the opening with an electrically-conductive binder including matrix material and fillers, the matrix material containing a thermosetting resin, the fillers including copper particles each coated with a tin bismuth alloy, the fillers dispersed in the matrix material so as to unite with the first and second electrically-conductive lands based on intermetallic compounds formed between the fillers and the first and second electrically-conductive lands, respectively;
pressing the first substrate against the second substrate with heating to soften the adhesive sheet; and
melting the tin bismuth alloy having a melting point higher than a softening temperature of the adhesive sheet by heating after the adhesive sheet has been softened;
heating and hardening the matrix material after the tin bismuth alloy has molten; and
heating and hardening the adhesive sheet after the matrix material has been hardened.
2. The method according to claim 1 , wherein the tin bismuth alloy of the fillers having the melting point higher than the softening temperature of the adhesive sheet.
3. The method according to claim 1 , wherein the tin bismuth alloy contains bismuth in a range from 50 wt % to 60 wt %.
4. A method of making a printed circuit board unit, comprising:
setting an adhesive sheet made of a thermosetting resin between an electronic component and a printed wiring board so that a first electrically-conductive land provided on the electronic component is opposed to a second electrically-conductive land provided on the printed wiring board through an opening formed in the adhesive sheet;
filling the opening with an electrically-conductive binder including matrix material and fillers, the matrix material containing a thermosetting resin, the fillers including copper particles each coated with a tin bismuth alloy, the fillers dispersed in the matrix material so as to unite with the first and second electrically-conductive lands based on intermetallic compounds formed between the fillers and the first and second electrically-conductive lands, respectively;
pressing the electronic component against the printed wiring board with heating to soften the adhesive sheet;
melting the tin bismuth alloy having a melting point higher than a softening temperature of the adhesive sheet by heating after the adhesive sheet has been softened;
heating and hardening the matrix material after the tin bismuth alloy has melted; and
heating and hardening the adhesive sheet after the matrix material has been hardened.
5. The method according to claim 4 , wherein the tin bismuth alloy of the fillers having the melting point higher than the softening temperature of the adhesive sheet.
6. The method according to claim 4 , wherein the tin bismuth alloy contains bismuth in a range from 50 wt % to 60 wt %.