JPS6058600B2 - How to attach electronic components to printed wiring boards - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for attaching an electronic component having a large number of connection terminals led out at equal intervals from an end surface of a main body to a printed wiring board.

Conventional Structure and Problems Conventionally, when an electronic component having a large number of connection terminals led out at equal intervals from the end face of the main body is soldered to a printed wiring board, the electronic component is soldered onto the printed wiring board. reflow soldering, in which a large number of connection terminals of the electronic components are bonded to each of the conductive foils arranged at equal intervals on the printed wiring board using cream solder previously provided on the printed wiring board; The attachment method is adopted.

In this reflow soldering method, the width of the conductive foil on the printed wiring board is made larger than the width of the connection terminal of the electronic component to be soldered.
(approximately 3 times).

In recent years, with the miniaturization of electronic devices, I
The miniaturization of ICs has progressed rapidly, and the number of connection terminals has increased and the terminal pitch has been minimized. For example, a flat pack type IC with 60 pins and a terminal pitch of 0 and 657Q has been put into practical use. Therefore, the width of the connection terminal and the dimension between the terminals are set to be approximately the same, and the width of the conductive foil of the printed wiring board and the dimension between the conductive foils are also set to be approximately the same. However, as shown in FIG. 1, the electronic components such as the above-mentioned ICs are connected to the printed wiring board 1 through the connection terminals of the electronic components 2, 3, 3...
Conductive foil 4, 4... to the related position corresponding to...
..., and connect the connection terminals 3, 3 as illustrated in Fig. 2.
......... predetermined conductive foil 4, 4...
...... and connect the connection terminals 3, 3...
When soldering is performed between the conductive foils 4, 4, . . . , and the conductive foils 4, 4, . The conductive foils 4, 4, . . . flow into the conductive foils 4, 4, .
There was a drawback that ... was short-circuited.

This is thought to occur because the solder 5 hardens due to surface tension when melted. Therefore, in order to eliminate the short circuit caused by the solder 5, the conductive foils 4, 4...
However, as shown in FIG. 2A, solder short circuits tend to occur near both ends of each side of the electronic component 2 in four directions. This is a flat back type 1C, and there are many opportunities for external force to be applied to the connection terminals at both ends of the connection terminals in four directions, and as a result, the leads are likely to bend and deform. Therefore, the printed wiring board corresponding to the connection terminals at both ends It is necessary to apply a larger amount of cream solder on the conductive foil than on the other connection terminal parts to increase the surface tension of the solder during reflow, and to automatically align it to the normal position. As a result, the relationship between the amount of solder and the area where the solder can be wetted is different from that of the other connecting terminals at the connection terminals at both ends, where the amount of solder is larger than the area where the solder can be wetted (which changes depending on the bent state of the lead), causing a solder short circuit. It depends on the reason why it happens more often. On the other hand, applying cream solder by varying the amount of solder to each of the conductive foils 4, 4, etc. arranged in parallel on each side requires an increase in the process of applying cream solder. There were problems in that it led to high manufacturing costs and was extremely difficult to adjust.
OBJECTS OF THE INVENTION An object of the present invention is to simplify the process of applying cream solder to conductive foils arranged at equal intervals on a printed wiring board, and to prevent short circuits caused by solder. The purpose is to provide a method for installing parts.

Structure of the Invention In order to achieve the above object, the method of attaching electronic components to a printed wiring board of the present invention is to attach only the conductive foils located at both ends of the group of conductive foils on the printed wiring board to all other conductive foils. The width is larger than the above width. The present invention is characterized in that cream solder for reflow soldering is continuously applied in a straight line to a group of conductive foils including conductive foils.

According to this mounting method, the cream solder can be applied continuously in a straight line to the conductive foil group, so it can be applied uniformly at once using a method such as screen printing. The cream solder application process can be significantly simplified. In addition, since the conductive foils at both ends of the conductive foil group are wide, the cream solder is attracted to the wide conductive foil parts during reflow soldering, preventing short circuits between adjacent conductive foils. be done. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention is shown in FIG.

Among the conductive foils 4, 4... of the printed wiring board 1, the conductive foils 4'', 4'' at both ends arranged in parallel
The width of . . . is made sufficiently larger than the width of the other conductive foils 4, 4, . Then, as shown in FIG. 4, conductive foils 4, 4 including a wide conductive foil 4, 4''...
Cream solder 6 is uniformly applied to the group arranged in parallel, and then electronic components 1 are mounted and reflow soldered.

When reflow soldering is performed in this way, the conductive foils 4, 4...
The cream solder applied continuously in a straight line to the groups of . . . . is attracted to the wide conductive foils 4'', 4'' at both ends of the groups. Therefore, as described above, the conductive foils 4, 4 arranged in parallel...
・Excess solder near both ends of conductive foil 4'', 4''...
There is no possibility of a short circuit occurring between the two.

In particular, according to this example, the solder joint area of the conductive foils at both ends of the conductive foils arranged in parallel is large, and the conductive foils 4, Since the cream solder 6 is applied to the groups arranged in parallel, the conductive foils 4'' at both ends are
The amount of solder at 4" is appropriate, and due to the parallel arrangement of the connecting terminals 3 of the electronic component 2, it is possible to perform strong soldering even when the connecting terminals at both ends are easily bent by external force. This is extremely advantageous in practical terms.

Effects of the Invention As described above, the mounting method of the present invention allows cream solder to be uniformly applied to conductive foils arranged at equal intervals at once, thereby preventing short circuits caused by solder during reflow soldering. It is something that can be done.

[Brief explanation of the drawing]

Fig. 1 is an explanatory perspective view showing how a general flat back type 1C is mounted on a printed wiring board, Fig. 2a is a front view showing its soldered state, and Fig. 2b is a Fig. 3a is a front view showing an embodiment of the present invention, Fig. 3b is a partially enlarged perspective view of the same, and Fig. 4a shows cream solder applied to a printed wiring board according to the same method. FIG. 4b is a partially enlarged perspective view of the front view showing this state. 1... Printed wiring board, 2... Electronic component, 3... Connection terminal, 4... Conductive foil, 5...
...Solder, 6...Cream solder.

Claims (1)

[Claims] 1. An electronic component having a large number of connection terminals led out at equal intervals from the end surface of the main body is mounted on a printed wiring board, and a large number of connection terminals of the electronic component are arranged at equal intervals on the printed wiring board. When bonding to each of the conductive foils by reflow soldering, only the conductive foils located at both ends of the group of conductive foils on the printed wiring board are formed sufficiently larger than the width of all other conductive foils. A method for attaching electronic components to a printed wiring board, characterized in that cream solder for reflow soldering is continuously applied in a straight line to a group of conductive foils including the wide range of conductive foils.