JPH04269894A - Soldering method for surface mount component on printed circuit board - Google Patents

Abstract

PURPOSE:To reduce thermal influence to a PC board and a surface mount component by soldering the mounting component to the board without using cream solder. CONSTITUTION:A pad 2 for soldering a surface mount component 7 on a PC board 1 is formed, and a through hole 5 is formed at a part formed with the pad 2. After the component 7 is adhesively secured to the board 1, the rear surface of the board 1 is dipped in a solder tank in which solder metal is melted to solder the component 7 to the board 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of soldering surface-mounted components to printed circuit boards.

0002

[Prior Art] Conventionally, when soldering surface-mounted components such as chip components to a printed circuit board (hereinafter abbreviated as PC board), a cream solder layer is placed on the pads formed on the surface of the PC board. is formed by screen printing, and the cream solder layer is melted using infrared rays or hot air to solder the surface-mounted components to the PC board.

However, in the conventional method as described above, a mask for screen printing the cream solder layer must be manufactured for each substrate, and therefore, there is a problem in that the manufacturing of the mask is expensive. Furthermore, in the conventional method described above, the cream solder layer is melted using infrared rays or hot air to solder the surface mount components to the PC board.
Another problem was that the thermal effects on the board and surface-mounted components were large.

0004

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and its object is to enable surface-mounted components to be soldered to a printed circuit board without using cream solder. It is an object of the present invention to provide a method for soldering surface-mounted components to a printed circuit board, which can reduce costs and reduce thermal effects on the PC board and surface-mounted components.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a first step of forming pads for soldering surface mount components on the surface of a PC board, and a portion where the pads are formed. a second step of forming a through hole in the PC board; and a third step of adhesively fixing the surface mount component to the surface of the PC board.
and a fourth step of immersing the back surface of the PC board in a solder bath containing molten solder metal after the third step.

[0006]

[Operation] In the present invention, when the back side of the PC board is immersed in a solder bath containing molten solder metal after the third step, the solder metal enters the through hole and causes surface tension, and the surface of the PC board is moved from the back side of the PC board to the surface of the PC board. Since it is sucked up to the side, electrodes of surface-mounted components can be soldered to pads formed on the surface of the PC board using solder metal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 to 5 show an embodiment of the method of the present invention. When surface-mounted components such as chip components are soldered to a PC board, first, as shown in FIGS. Pad 2 for soldering surface mount components to the surface of the board 1
is formed together with the wiring pattern 3 by printing or the like. Next, as shown in FIG. 3, the front and back surfaces of the PC board 1 except for the pads 2 are covered with a resist 4, and through holes 5 are formed in the areas where the pads 2 are formed. Note that at this time, as shown in FIG. 4, a metal film 6 electrically connected to the pad 2 may be formed on the inner surface of the through hole 5.

Next, as shown in FIG. 5, a surface mount component 7 is placed on the surface of the PC board 1, and the surface mount component 7 is fixed to the surface of the PC board 1 with a thermosetting adhesive 8. After adhesively fixing the surface mount component 7 to the surface of the PC board 1,
Dip the back side of the board into a solder bath (not shown) containing molten solder metal. Then, as shown in FIG. 6, the solder metal 9 enters the through hole 5, causing surface tension. The solder metal 9 that has entered the through hole 5 is sucked up from the back side of the PC board 1 to the front side, and as shown in FIG.
It is fixed to the pad 2 formed on the surface of the surface mount component 7 and the electrode 10 formed on the lower surface of the surface mount component 7.

Therefore, in the above embodiment, the pad 2 formed on the surface of the PC board 1 and the electrode 10 of the surface mount component 7 can be soldered with the solder metal 9, and cream solder is used as in the conventional method described above. There is no need to create a mask for each board to screen print the layer, or melt the cream solder layer using infrared rays or hot air to solder the surface mount components. Thermal influence on the board 1 and surface-mounted components 7 can be reduced.

In addition, in the above embodiment, it is only necessary to dip the back side of the PC board 1 into the solder bath, so when another surface mount component 11 is soldered to the back side of the PC board 1 as shown in FIG. 9, when soldering the discrete components 12 to the surface of the PC board 1, these components 11, 1
2 can be simultaneously soldered to the surface of the PC board 1 together with the surface mount component 7 using solder metal.

It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0013]

As explained above, the present invention includes the first step of forming pads for soldering surface-mounted components on the surface of a PC board, and forming through holes in the areas where the pads are formed. a second step, and the surface mount component is
The method includes a third step of adhesively fixing the PC board to the surface of the PC board, and a fourth step of immersing the back surface of the PC board into a solder bath containing molten solder metal after the third step. Therefore, by dipping the back side of the PC board into a solder bath containing molten solder metal after the third step, the solder metal will enter the through hole and cause surface tension, causing P
Since it is sucked up to the surface side of the PC board, it is possible to solder the electrode of the surface mount component to the pad formed on the surface of the PC board using solder metal. Therefore, there is no need to create a mask for each board to screen print the cream solder layer, or to melt the cream solder layer using infrared rays or hot air to solder surface mount components, thereby reducing costs. At the same time, thermal effects on the PC board and surface-mounted components can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a printed circuit board for explaining a first step in an embodiment of the present invention.

FIG. 2 is a sectional view taken along line A-A in FIG. 1;

FIG. 3 is a cross-sectional view of the printed circuit board for explaining the second step in the same example.

FIG. 4 is a sectional view of a printed circuit board for explaining a modification of the same embodiment.

FIG. 5 is a cross-sectional view of the printed circuit board for explaining the third step in the same example.

FIG. 6 is a cross-sectional view of the printed circuit board for explaining the fourth step in the same example.

FIG. 7 is a cross-sectional view of the printed circuit board after the fourth step in the same example.

FIG. 8 is a sectional view of a printed circuit board for explaining an application example of the embodiment.

FIG. 9 is a sectional view of a printed circuit board for explaining an application example of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...PC board, 2...pad, 3...wiring pattern, 4...resist, 5...through hole, 7...surface mount component, 8...adhesive, 9...solder metal.

Claims (1)

[Claims] 1. A first step of forming a pad for soldering a surface mount component on the surface of a printed circuit board, a second step of forming a through hole in a portion where the pad is formed, and a second step of forming a through hole in the part where the pad is formed; It is characterized by comprising a third step of adhesively fixing the component to the surface of the printed circuit board, and a fourth step of immersing the back side of the printed circuit board in a solder bath containing molten solder metal after the third step. How to solder surface mount components to a printed circuit board.