Metal working – Method of mechanical manufacture – Electrical device making
Patent
1988-08-26
1990-12-25
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
29833, 21912163, 228 491, 2281802, H05K 334
Patent
active
049792903
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and an apparatus for soldering an electronic component of a semiconductor device, e.g., a flat package IC to a printed circuit board.
BACKGROUND ART
Conventionally, an automatic soldering apparatus has been used for mounting and soldering an electronic component 1 having lead arrays 3 extending substantially horizontally from the respective sides of its main body portion 2 on a predetermined position on a circuit board (not shown).
One example of such soldering process presses a heater chip against the lead terminal arrays 3 of the electronic component 1 and thereafter heats the heater chip, thereby performing soldering. However, since such a soldering process uses a physical contact, various problems, e.g., a positional error of the electronic component upon contact with the heater chip occur. In order to solve these problems, a soldering apparatus has recently been developed wherein a soldering method using a non-contact process such as a laser beam is employed.
One of the soldering apparatuses using such a non-contact process has a bench for placing a circuit board on which an electronic component 1 is temporarily fixed, a laser emitting section arranged to oppose the circuit board on the bench, and a laser moving means such as an X-Y table on which the laser emitting means is mounted thereon for moving the laser emitting means in the X-Y direction on the circuit board.
In the soldering process of such soldering apparatus, the laser moving means is driven to move the laser emitting means in the X-Y direction, so that a laser beam A sequentially radiates the lead terminal arrays 3.
There is another process for soldering in which the laser beam is used as a linear spot, and simultaneously radiates the terminals of a lead terminal array 3 on one side of an electronic component.
However, in the conventional soldering process described above, when one lead terminal is soldered the laser beam is to be moved to the next lead terminal for serially soldering the terminals, or when one terminal array is simultaneously soldered by using the linear type beam spot, another terminal array should be soldered continuously. Therefore, one lead terminal can be thermally influenced by an adjacent lead terminal to cause undesirable results. For example, adjacent lead terminals are connected through solder and are electrically connected each other, thereby resulting in a solder bridge.
In addition, local temperature rise in the vicinity of the laser radiated portion enhances the above problem. This problem tends to easily occur particularly in a narrow pitch flat package IC in which the lead pitch is for example 0.5 mm or 0.65 mm. A technique for solving this problem has been desired.
Further, since all the lead terminal arrays are soldered with a single laser beam, reduction in the soldering time is limited due to the scanning performance of the laser beam.
The present invention has been made in order to solve the drawbacks of conventional soldering process. Since the present invention uses a high energy beam such as a laser beam and radiates two-dimentionally and continuously each lead terminal array in a plurality of times, the temperature rise rate and the temperature distribution in the vicinity of the lead terminals can be uniformed. Therefore, various problems arising from the non-uniformed temperature rise rate and temperature distribution in the vicinity of the lead terminals, e.g., a solder bridge wherein adjacent lead terminals are connected through solder and are electrically conducted, can be prevented, thereby resulting in an increase of solder operation precision.
Furthermore, the present invention uses a plurality of beams for radiating different lead terminal arrays of an electronic component, thereby greatly reducing the soldering time.
Furthermore, in the present invention soldering operation and electronic conveying/mounting operation are performed simultaneously, thereby simplifying the operation.
Furthermore, since in the present invention s
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Arbes Carl J.
Hall Carl E.
Kabushiki Kaisha Toshiba
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