Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-04-26
2003-06-03
Eley, Timothy V. (Department: 3723)
Metal working
Method of mechanical manufacture
Electrical device making
C029S825000, C029S811200, C029S412000, C029S413000
Reexamination Certificate
active
06571469
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a modular board to be electrically connected to a mother board via soldering.
2. Description of the Related Art
In order to achieve high-density design, current electrical circuits are partially assembled into a modular board to facilitate intermediate inspection and mounting, and the modular board is then mounted on a mother board (as disclosed in Japanese Unexamined Patent Application Publication No. 63-204693).
Such conventional modular boards include a rectangular and thin insulator board which is fabricated by alternately laminating insulation resin materials and conductive wiring patterns.
Mounted on the modular board are active elements such as transistors, and passive elements such as resistors and capacitors. These elements are interconnected by a wiring pattern and define an electrical circuit. The end surface portion of the edge of the modular board has a plurality of end surface through holes which are filled with edge electrodes for feeding power from a mother board external to the electrical circuit and inputting and outputting signals to and from the electrical circuit.
The modular board thus includes a modularized electrical circuit assembled thereon for performing a desired signal process on signals input from the mother board. During assembly, the modular board is stacked on the mother board, and the edge electrodes are connected to electrical pads on the mother board using soldering to mount the modular board on the mother board.
The above-referenced modular board is fabricated by alternately laminating rectangular insulators of resin material and conductive wiring patterns.
Since a thermal expansion ratio is different between the resin material of the board and the wiring, the board partially suffers from distortion such as warpage depending on the layout and density of the wiring pattern when the board is heated during the process of the board or during the soldering of the board.
In the conventional art, the modular board is often partially separated from the mother board due to warpage when the modular board is mounted on the mother board. The warpage of the modular board leads to a connection failure on some of the edge electrodes, thereby deteriorating the reliability of the modular board. The conventional modular board is configured to be as thin as possible, and is thus subject to increased warping even under a slight degree of heating. Therefore, it is difficult to reliably mount the modular board onto the mother board.
SUMMARY OF THE INVENTION
To overcome the above-described problems with the prior art, preferred embodiments of the present invention provide a method of manufacturing a modular board which enables edge electrodes to be securely connected to a mother board even when the modular board is subject to warpage.
One preferred embodiment of the present invention provides a method for manufacturing a modular board and includes the steps of opening a through-hole in a bare board, providing a back electrode surrounding the through-hole on the bottom surface of the bare board, arranging an edge electrode, connected to the back electrode, partially or entirely on the inner wall of the through-hole, cutting the bare board along the through-hole to produce a split board having the back electrode and the edge electrode and a remaining bare board, providing an adhesive compound containing an oxide removal substance on the periphery of the through-hole, attaching solid solder to the adhesive compound, heating the split board and the remaining bare board to melt the solid solder, and cooling and solidifying the molten solder on the edge electrode and the back electrode for bonding.
The split board having the back electrode and the edge electrode and the remaining bare board are preferably formed from the bare board. By placing the split board back into the remaining bare board, the through-hole is again provided between the split board and the remaining bare board. In this way, the split board is separated from the bare board prior to attaching the solid solder to the edge electrode.
The solid solder is held in position by the adhesive compound because the adhesive compound containing the oxide removal substance is provided around the through-hole followed by the placement of the solid solder on the adhesive compound. When the split board and the remaining bare board are heated, the adhesive compound acts as a catalyst, and the solid solder starts melting at the portion thereof in contact with the adhesive compound and flows into the through-hole. Since the edge electrode is provided in the through-hole, the molten solder securely attaches to the edge electrode. A portion of the molten solder flows from the edge electrode and covers the back electrode.
Since the molten solder has a substantially spherical shape and surface tension and attaches to the edge electrode and the back electrode, a portion of the molten solder swells and expands out of the through-hole. When the split board, which has already been cut from the bare board, is separated from the bare board, the split board becomes a modular board, and the molten solder swells from the bottom surface thereof toward the mother board. The swollen solder is drawn into a gap between the modular board and the mother board, thereby securely connecting the edge electrodes of the modular board to the electrical pads of the mother board.
Another preferred embodiment of the present invention provides a method for manufacturing a modular board and includes the steps of providing a back electrode on the bottom surface of a bare board, opening a through-hole in the bare board in the back electrode, arranging an edge electrode, connected to the back electrode, partially or entirely on the inner wall of the through-hole, cutting the bare board along the through-hole to produce a split board having the back electrode and the edge electrode and a remaining bare board, providing an adhesive compound containing an oxide removal substance on the periphery of the through-hole, attaching solid solder to the adhesive compound, heating the split board and the remaining bare board to melt the solid solder, and cooling and solidifying the molten solder on the edge electrode and the back electrode for bonding.
The method for manufacturing a modular board preferably includes the step of removing the back electrode on the bottom surface of a portion of the bare board becoming the remaining bare board and the edge electrode on the inner wall of the through-hole of the portion of the bare board becoming the remaining bare board, prior to the cutting of the bare board.
This arrangement prevents the molten solder from sticking to the remaining bare board. After the molten solder is cooled and solidified, the split board is easily separated from the remaining bare board.
The adhesive compound is preferably provided, on the top surface of the split board, in contact with the edge electrode.
When the split board is heated with the solid solder attached to the adhesive compound, the solid solder begins melting at the portion thereof in contact with the adhesive compound. Since the adhesive compound remains in contact with the edge electrode, the molten solder attaches to the edge electrode while partially flowing along the edge electrode to cover the back electrode. As a result, the solder bonds to both the edge electrode and the back electrode.
The adhesive compound is preferably provided on the bottom surface of the split board and in contact with the back electrode.
When the split board is heated with the solid solder attached to the adhesive compound, the solid solder begins melting at the portion thereof in contact with the adhesive compound. Since the adhesive compound remains in contact with the back electrode, the molten solder attaches to the back electrode while partially flowing along the back electrode to reach the edge electrode. As a result, the solder bonds to both the edge electrode and the back electrod
Doi Hirofumi
Nagai Iku
Nakaji Hiroyuki
Nakasone Junichi
Nakaya Kazuyoshi
Eley Timothy V.
Grant Alvin J.
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