Metal fusion bonding – Process – Plural joints
Reexamination Certificate
1999-06-23
2001-08-28
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
Plural joints
C228S180100, C228S179100, C228S178000
Reexamination Certificate
active
06279814
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a semiconductor assembly technology and, more particularly, to a soldering apparatus for providing a fixed quantity of solder piece to a printed circuit board and a method of soldering a circuit component to the printed circuit board.
DESCRIPTION OF THE RELATED ART
A module is a basic component unit of an electric system, and electric circuit components are assembled on a rigid or flexible board during a fabrication of the module. Bare chips are, by way of example, mounted on a printed circuit board, and a flexible board may be assembled with a rigid board. Thus, a micro-connecting technology is an important factor of the fabrication of the module.
A typical example of the micro-connecting technology is known as a solder printing. The solder printing process has the following sequence. First, the manufacturer prepares a printed circuit board, a solder paste and a mask. A conductive wiring pattern is printed on the printed circuit board, and solder powder and binder form the solder paste. The mask has through-holes, and is aligned with the printed circuit board. Junctions of the conductive wiring pattern are exposed to the through-holes of the mask, and the solder paste is screen printed through the mask on the printed circuit board. Finally, bare chips are mounted on the printed circuit board, and the pins of the bare chips are soldered to the junctions of the conductive wiring pattern by applying heat to the solder.
Although the screen-printing exactly locates the solder paste on the junctions, the amount of solder paste is not constant. In particular there is a tendency to scale down the module, and the junctions of the conductive wiring pattern are arranged to be close to one another. In this situation, the through-holes of the mask are miniaturized, and the miniature through-holes do not allow the solder paste to smoothly pass therethrough. This results in the fluctuation of the amount of solder paste on the junctions, and an electric circuit component is liable to be disconnected from the printed circuit board due to shortage of the solder.
SUMMARY OF THE INVENTION
It is therefore an important object of the present invention to provide a soldering apparatus which strongly fixes a component element to a target plate with a fixed amount of solder.
It is also an important object of the present invention to provide a method of strongly soldering a component element to a target plate with a fixed amount of solder.
To accomplish the object, the present invention proposes to cut out a piece of solder from a solder sheet onto a feeder which moves the piece of solder to a junction.
In accordance with one aspect of the present invention, there is provided a soldering apparatus comprising a solder piece provider for supplying at least one solder piece on a target layer, the solder piece provider comprising a die unit having at least one through-hole, a conveying mechanism selectively supplying a solder plate and a target layer in such a manner that the die unit is overlapped with one of the solder plate and the target plate, a punching mechanism moving a punching pin into and out of the through-hole so as to cut out a solder piece from the solder plate so as to leave the solder piece in the through hole, and a feeding mechanism moving a feeder pin in the through-hole so as to press the solder piece against the target layer.
In accordance with another aspect of the present invention, there is provided a micro-connecting method comprising the steps of: a) providing a solder plate on a die unit having at least one through-hole; b) pressing a punching pin against the solder plate so as to cut out a solder piece from the solder plate, the solder piece being left in the through-hole; c) removing the solder plate from the die unit; d) aligning a junction point of a target layer with the through-hole; e) moving a feeder pin in the through-hole so as to press the solder piece against the junction point; and f) soldering a component element to the junction by using the solder piece.
REFERENCES:
patent: 5433368 (1995-07-01), Spigarelli
patent: 5573170 (1996-11-01), Sasaki et al.
Inoue Akifumi
Takeda Koshiro
Elve M. Alexandra
Ostrolenk Faber Gerb & Soffen, LLP
Yamaha Corporation
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