JPH05226824A - Method and apparatus for coating preliminary solder on printed wiring board - Google Patents

Abstract

PURPOSE:To prevent a short-circuit between electrodes due to stickout when mounting devices on a printed wiring board, by forming a uniform and unexcess amount of solder on each electrode when pre-coating solder to each electrode on the printed wiring board. CONSTITUTION:An apparatus comprises a rotary table 7 for removably holding a printed wiring board 1, a motor 8 for rotating the rotary table 7, and a controller for controlling the rotational speed of the motor 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-soldering method and apparatus for soldering a device (circuit element or semiconductor device) having a large number of leads to an electrode on a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, as a method of mounting a semiconductor device on a printed wiring board, a tape carrier device or a device having many lead groups such as a flat device is widely used by surface mounting by soldering. Has been. As a method by this soldering, first, cream solder is preliminarily printed on the electrodes of the printed wiring board, and the lead group of the device is allowed to stand on the electrodes, and then the cream solder is melted by heating to form electrodes. And those to solder each lead group, and in addition to this, after applying solder by plating in advance on the electrodes of the printed wiring board,
A method in which each lead group of the device is left stationary on this and the lead group is soldered to the electrode by pressing the lead group onto the electrode with a heating tool is mainly used.

[0003]

However, in any of the above methods, the solder coated on the electrodes is swelled,
There is no problem if there is a variation in the amount of solder and the lead gap of the device is wide, but if it becomes narrow due to miniaturization (for example, 0.4 mm or less), short-circuiting or soldering between adjacent leads will not occur. You can lead. Therefore, the present invention intends to solve the above-mentioned problems and to provide a method and an apparatus for keeping the amount of preliminary solder constant at a necessary minimum.

[0004]

A printed wiring board coated with preliminary solder is detachably mounted on a rotary table, and the rotary table is rotated at a required rotation speed by an operation of a rotation control unit, so that the table is rotated. A centrifugal force is applied to the upper printed wiring board to remove the excess.

[0005]

The preliminary solder applied on the electrodes of the printed wiring board is rotated by selecting the optimum rotation speed on the rotary table, and the excess solder is scattered by the centrifugal force, so that the solder is uniformly left on each electrode. ..

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 illustrates a tape carrier device.
On the connection terminals 5 of the device 6 (for example, LSI) having Si as a base material, a plurality of Cu-made leads 4, 4, ... With a parent solder metal such as Sn, Au plated on the surface are inseparably attached, and The outer ends of the leads 4 are appropriately bent and are made of Cu or Ni on the printed wiring board 1 or a laminated layer thereof, and a plurality of electrodes 2, 2 plated with a parent solder metal such as Sn or Au on the surface thereof. Is placed on the top of the solder 3 which has been pre-soldered by printing, ripping, or the like in advance, and the leads 3, 4 are connected to the electrodes 2, 2 by heating and melting the solder 3. is there.

Next, a method of applying preliminary solder according to the present invention will be described. As shown in FIG. 2, printing is performed near one end of a plurality of parallel electrodes 2, 2, ...
In addition, the solder 3 is applied by a solder lip or the like, and particularly in the case of the solder lip, the ripping is performed in a masked state in advance in order to prevent the solder from adhering outside the predetermined range. But actually the electrode 2,
When the distance between the two electrodes is small, the solder 3a adheres in a bridge state between the electrodes to cause a short circuit as shown in FIG. 2, or the solder 3a is on only a single electrode but is excessive like the solder 3b. And it sticks out to the side. Further, in the case of the printing method, if the electrode interval is narrow even before the bridge state occurs, and the amount of preliminary solder is large, the solder melted by applying pressure when soldering the lead 4 and the electrode 2 It overflows to the part and the adjacent parts are fused together to form a short circuit. Therefore, as shown in FIG. 2, it is necessary to remove the short-circuit solder 3a and the protruding solder 3b thereafter. Therefore, an apparatus used for carrying out the method of the present invention excluding the above-mentioned drawbacks is a rotary table 7 for detachably attaching and holding the printed wiring board 1 of FIG. 2 as shown in FIG. 3, and a motor for driving the rotary table 7. 8 and a rotation control unit (not shown) that controls the rotation speed of the motor 8. By operating the control unit, a suitable amount of pre-solder is suitable for remaining on the electrodes 2, 2, ... Rotation can be selected, and when the motor 8 is rotated, the preliminary solder applied on the electrodes 2, 2, ... Of the printed wiring board 1 receives a centrifugal force. In other words, the effect of centrifugal force is large in the area where the amount of coating is large, and becomes small in the area where the amount is small, and only the amount of solder enough to balance the adhesive force of the solder and the centrifugal force remains on each electrode. By selecting the speed, it is possible to freely control the remaining amount of preliminary solder.

In this way, by rotating the rotary table 7, the printed wiring board 1 rotates and the short-circuit solder 3a
Since the protruding solder 3b has a large amount of solder, the protruding solder 3b receives a large centrifugal force and is shaken off. As shown in FIG.
2, ..., an equal amount of solder 3,3, ... remains, and the leads 4,4, ... of the device 6 are placed on the solder 3,3 ,.
Even if the end is heated and pressure-bonded, the pressure at that time does not cause the solder to stick out to the extent that the solder contacts the adjacent electrode.

[0009]

As described above, the present invention makes it possible to freely change the remaining amount of the preliminary solder by controlling the rotation speed and time, and it is possible to easily change the amount by a very simple operation. .. Moreover, the structure of the apparatus is extremely simple.

[Brief description of drawings]

FIG. 1 is a partially enlarged vertical sectional view of a connection state between a device and a printed wiring board.

FIG. 2 is an enlarged plan view of a plane portion in a state where preliminary solder is provided on a printed wiring board.

FIG. 3 is a perspective view of the device of the present invention.

FIG. 4 is a partial perspective view of a printed wiring board showing an ideal state of preliminary soldering.

[Explanation of symbols]

 1 Printed wiring board 2 Electrode 3 Preliminary solder 7 Rotating table 8 Motor

Claims (2)

[Claims] 1. A pre-solder applied to an electrode surface of a printed wiring board is heated and melted, and a centrifugal force is applied to the printed wiring board to scatter and remove an excessive amount of the pre-solder. Pre-solder application method on printed wiring board. 2. A rotary table on which a printed wiring board having pre-soldered solder is placed, a motor for rotating the rotary table at a predetermined speed, and a controller for appropriately controlling the rotational speed of the motor. A preliminary solder coating device on a printed wiring board.