JPH07183647A - Printed circuit board and electronic component mounting method on printed circuit board - Google Patents

Abstract

PURPOSE:To ensure soldering of a lead of an electronic part to land of a circuit pattern of a printed-circuit board. CONSTITUTION:On a printed-circuit board 3, 4 which a solder precoat part 10 is formed on a land 5 of a circuit pattern 4, a recess 9, where leads 2 of an electronic part 1 land, is formed in the center of the solder precoat part 10. As a result, positional deviation of the electronic part 1 and sinking of the leads 2 when the solder precoat part 10 melts are eliminated so that the posture of the electronic part 1 is maintained horizontal and all leads 2 can be soldered with certainty to the land 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board for mounting leads of an electronic device by soldering and a method for mounting an electronic device on the printed circuit board.

[0002]

2. Description of the Related Art As a printed circuit board on which electronic parts are mounted, there is known a printed circuit board in which a solder precoat portion is formed on a land of a circuit pattern formed on the surface of the printed circuit board by a solder plating means or the like.

7 and 8 are cross-sectional views of a conventional printed circuit board on which electronic parts are mounted. In FIG. 7, reference numeral 1 is an electronic component, and leads (electrodes) 2 are formed on both sides of the electronic component. A solder precoat portion 6 is formed on a land (electrode) 5 at the tip of the circuit pattern 4 formed on the surface of the printed board 3, and a flux 7 is applied to the solder precoat portion 6 to form an electronic component. It is equipped with 1. The printed board 3 is sent to a heating furnace, and the solder precoat portion 6 is heated and melted to solder the leads 2 to the lands 5.

[0004]

However, since the area of the solder precoat portion 6 on which the leads 2 of the electronic component 1 are mounted is small in the conventional printed circuit board 3 described above, the printed circuit board 3 is mounted in the X direction by an electronic component mounting apparatus, for example. When the electronic components 1 are mounted on the solder precoat portion 6 one after another while being horizontally moved at high speed in the or Y direction, the electronic components 1 are displaced and lead 2 as shown by a chain line in FIG.
However, there is a problem in that it easily falls off from the solder precoat portion 6.

After mounting the electronic component 1, the printed circuit board 3 is sent to a heating furnace to heat and melt the solder precoat portion 6 for soldering. The precoat portion 6 does not melt at the same time. FIG. 8 shows the solder precoat portion 6 on the right side.
The case where the left solder precoat portion 6 is melted is shown prior to this. In this case, since the left solder precoat portion 6 is melted first, the left lead 2 largely sinks and the electronic component 1 tilts, so that the right lead 2 floats up from the solder precoat portion 6 and is soldered. There was a problem that it was difficult to do so.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the conventional printed circuit board described above and to provide a printed circuit board and a method of mounting electronic parts on the printed circuit board, by which the leads of the electronic component can be reliably soldered to the land. To do.

[0007]

To this end, according to the present invention, a concave portion is formed in the center of a solder precoat portion formed on a land of a circuit pattern of a printed circuit board, and a lead of an electronic component is formed in the concave portion. The tip part is fitted.

[0008]

According to the above construction, the solder precoat portion does not exist at the portion where the tip of the lead is fitted or the thickness of the solder precoat portion is thin, so that even if the solder precoat portion is heated and melted, the lead Does not significantly sink, and therefore, the variation in the melting rate of the solder precoat portion does not cause the electronic component to tilt and cause defective soldering.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view of an electronic component and a printed circuit board according to an embodiment of the present invention. A lead 2 is provided on the side wall of the electronic component 1.
Are extended at a narrow pitch. A solder precoat portion 10 is formed on the land 5 at the tip of the circuit pattern 4 formed on the surface of the printed board 3. As shown in the figure, the solder precoat portion 10 is formed only on both side portions of the land 5, and the center portion thereof is the recessed portion 9.

Next, a method of mounting the electronic component 1 on the printed board 3 will be described. 2 is a cross-sectional view of a printed circuit board according to an embodiment of the present invention in which flux is applied, FIG.
5 is a front view showing a state where electronic components are mounted on the printed circuit board, FIG. 4 is a sectional view of a heating furnace for the printed circuit board, and FIG.
(A), (b), (c), (d) is a perspective view and sectional drawing of the land vicinity of the same printed circuit board.

First, as shown in FIG. 2, the flux 13 is applied by bringing the screen mask 11 of the screen printing device into contact with the upper surface of the printed circuit board 3 and sliding the squeegee 12 leftward on the screen mask 11. To do.
A pattern hole is opened at a position corresponding to the land 5 of the screen mask 11. Therefore, the flux 13 is formed on the land 5 and the solder precoat portion shown in FIG. 5A as shown in FIG. 5B. Is applied. Generally,
The solder precoat portion is subjected to fusing in order to make the solder structure dense. However, since the shape of the solder precoat portion is deformed when the fusing is performed, this is not subjected to fusing.

Next, as shown in FIG. 3, the electronic component 1 is vacuum-sucked by the nozzle 15 of the head 14 of the electronic component mounting apparatus,
The electronic component 1 is mounted on the printed board 3 at predetermined coordinate positions while the printed board 3 is horizontally moved in the X direction and the Y direction. FIG. 5C is a cross-sectional view near the land on which the electronic component 1 is mounted. Since the tip ends of the leads 2 are positioned by landing in the recessed portions 9, even if the printed circuit board 3 is horizontally moved at high speed in the X and Y directions, the electronic component 1 is displaced and the leads 2 are landed. It does not fall from 5.

Next, the printed circuit board 3 is sent to a heating furnace,
The solder precoat portion 10 is heated and melted to perform soldering. In FIG. 4, a conveyor 17 is provided inside the heating furnace 16.
Is provided. A fan 18 and a heater 19 are arranged above the conveyor 17. The printed circuit board 3 is moved from the inlet 20 of the heating furnace 16 toward the outlet 21 of the conveyor 1
The solder precoat portion 10 is melted by being conveyed by 7, and the printed circuit board 3 is heated during that time, and then the printed circuit board 3 is cooled to solidify the melted solder, whereby the soldering is completed.

FIG. 5 (d) is a perspective view of the land near the end of the soldering, and 10a is the solder precoat portion 10.
Is melted and solidified solder. Since the solder precoat portion 10 does not exist in the portion where the tip of the lead 2 is grounded, the lead 2 does not sink even if the solder precoat portion 10 melts. Therefore, even if the melting speed of the solder precoat portion 10 varies. The electronic component 1 maintains a horizontal posture, and all the leads 2 can be reliably soldered to the lands 5.

FIG. 6 is a perspective view of the vicinity of a land of a printed circuit board according to another embodiment of the present invention. As shown in the figure, a thin solder precoat portion 10 ′ is formed between the lands 10 formed on both sides of the land 5, and the upper portion thereof is a recess 9. In this product, the tip of the lead 2 is fitted on the thin solder precoat portion 10 'for soldering, but since the thin solder precoat portion 10' has a small amount of solder, the thin solder precoat portion 10 'is melted. However, the leads 2 do not largely sink, and therefore, even if the melting speed varies, the electronic component 1 can maintain a substantially horizontal posture and all the leads 2 can be soldered to the lands 5. As described above, various concrete shapes of the solder precoat portion are conceivable. In short, by reducing the amount of solder in the portion where the tip of the lead 2 is grounded, even if the melting speed of the solder precoat portion varies, the electronic component Be careful not to tilt.

[0016]

As described above, according to the present invention, by mounting the electronic component by landing the lead of the electronic component in the recessed portion, displacement of the electronic component can be prevented and the solder precoat portion can be melted. Even if the speed varies, the leads should not sink deeply to prevent the electronic components from tilting, and the posture of the electronic components should be kept horizontal to prevent the electronic components from being displaced, and the solder precoat part should be heated and melted in that state. As a result, the leads of the electronic component can be reliably soldered to the lands of the printed board.

[Brief description of drawings]

FIG. 1 is a perspective view of an electronic component and a printed circuit board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a printed circuit board according to an embodiment of the present invention in which flux is applied.

FIG. 3 is a front view of a printed circuit board according to an embodiment of the present invention in which electronic components are mounted.

FIG. 4 is a sectional view of a heating furnace for a printed circuit board according to an embodiment of the present invention.

FIG. 5 (a) is a perspective view of the vicinity of a land of a printed circuit board according to one embodiment of the present invention. (B) is a perspective view of the vicinity of a land of a printed circuit board according to one embodiment of the present invention. Sectional view of the vicinity of the land of the printed circuit board (d) Perspective view of the vicinity of the land of the printed circuit board of one embodiment of the present invention

FIG. 6 is a perspective view near a land of a printed circuit board according to another embodiment of the present invention.

FIG. 7 is a sectional view of a printed circuit board on which a conventional electronic component is mounted.

FIG. 8 is a sectional view of a printed circuit board on which a conventional electronic component is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic component 2 Lead 3 Printed circuit board 4 Circuit pattern 5 Land 9 Recessed part 10 Solder precoat part 13 Flux

Claims (2)

[Claims] 1. A printed circuit board having a solder precoat portion formed on a land of a circuit pattern, wherein a recessed portion for landing a tip of a lead of an electronic component is formed at a central portion of the solder precoat portion. . 2. A step of applying a flux onto a solder precoat portion formed on a land of a printed circuit board, and a tip portion of a lead of the electronic component is fitted into the recess formed in the center of the solder precoat portion. And mounting an electronic component on the printed circuit board, and heating and melting the solder precoat portion, and then solidifying and soldering the electrode of the electronic component onto the land. And a method for mounting electronic components on a printed circuit board.