JPH09205273A - Squeegee unit and cream solder supply method using squeegee unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability for printing cream solder onto a printed wiring board where a narrow-pitch part and a wide-pitch part are mixedly mounted by the stencil method. SOLUTION: In a squeegee unit 1 used to supply cream solder to the pad of a printed wiring board by the stencil method, who squeegee fins 2a and 2b which are arranged so that they are overlapped with a desired interval are provided and one squeegee fin edge part 3b is made higher than the other squeegee fin edge 3a. In a method for supplying cream solder using the squeegee unit 1, a squeegee plate at a side where the edge part is made higher out of the two squeegee fins 2a and 2b is set to the side where the squeegee unit 1 advances and cream solder is supplied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a squeegee unit used for supplying cream solder to a pad of a printed wiring board by a stencil method and a method for supplying cream solder using the squeegee unit.

[0002]

2. Description of the Related Art A reflow soldering method is known as a method for soldering an electronic component such as a surface mount IC to a printed wiring board. In this method, cream solder is supplied to a pad formed on a printed wiring board, IC leads and the like are temporarily fixed to this cream solder, and the cream solder is melted by heating in a reflow furnace and soldering.

The stencil method is widely known as one method of supplying cream solder to the pad. In this stencil method, an opening corresponding to a pad for supplying cream solder to a stainless plate or a nickel plate is processed by an etching method or the like to first make a metal mask (also called a stencil plate). Then, this metal mask is brought into close contact with the printed wiring board, and 1 amount of cream solder determined by the thickness of the metal mask is put on the metal mask.
A squeegee unit consisting of a single squeegee is used to apply the film so that it extends flat, and then the metal mask is peeled off to supply the cream solder that has entered the opening of the metal mask to the pad.

Due to the necessity of designing a printed wiring board, a printed wiring board has a pad for a narrow pitch component having a lead pitch of 0.4 mm or less and a pad for a wide pitch component such as a tantalum capacitor. It may be mixed on the board.

[0005]

Problems of Prior Art FIGS. 3 and 4 show an example in which cream solder coating is applied to a mixed printed wiring board of narrow pitch and wide pitch parts using a conventional squeegee unit. Pads for narrow-pitch parts have a narrow metal mask opening size. For example, in the case of a QFP component having a pad interval of 0.4 mm, the pad width is very narrow at 0.2 mm, which makes it difficult for cream solder to enter the metal mask opening. Therefore, it is necessary to increase the pressing force of the edge portion of the squeegee fin that is in contact with the metal mask for the purpose of strengthening the force of the cream solder to enter the metal mask opening.

On the other hand, pads for wide pitch components have a wide metal mask opening size. For example, tantalum capacitor (S
VD) is about 3 mm. When the pressing force of the squeegee unit is increased in such a wide metal mask opening, the cream solder is scooped out, resulting in insufficient supply of solder to the required amount. FIG. 3-A is an overall view of the passing state of the squeegee, and FIGS. 3-B and 3-C are enlarged views of the passing portion of the squeegee with time. The squeegee fins 2 of the squeegee unit 1 that pass through the wide pitch holes 15 of the metal mask 11 supply the cream solder 13 to the pads 12 of the printed wiring board 10 and at the same time press the edge portion 3 more than necessary. Since it is put in the opening 15, the surface of the cream solder 13 supplied to the opening 15 is scraped deeper than the surface of the metal mask 11.

If the squeegee pressing force is adjusted to the wide pitch component, it becomes difficult for the cream solder to enter the metal mask opening portion of the narrow pitch component, resulting in insufficient supply of solder due to defective removal of the cream solder. FIG. 4-A is an overall view of a passing state of a squeegee, FIG. 4-B is an enlarged view of a main part of a narrow pitch opening portion, and FIG. 4-C is an enlarged view of a main part with a metal mask removed. Although the squeegee fin 2 supplies the cream solder 13 to the narrow-pitch holes 14, the pressing force of the edge 3 is weak, so that the cream solder 13 is not sufficiently pressed and the supply becomes insufficient. Sometimes the cream solder 13 does not reach the pad 12, and when the metal mask 11 is peeled off, the cream solder 13 does not reach the pad 12.
The metal mask may not be left on the upper surface and may be removed while being attached to the opening 14 of the metal mask.

In order to solve such a problem, the pressing force of the squeegee is changed to supply the cream solder in two steps, or an intermediate pressing force between the two is set depending on the intuition of an expert. However, in the case of the former, there is a problem that it takes time, and in the case of the latter, there is a problem that only an expert can work.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and when a cream solder is supplied to a pad of a printed wiring board on which a plurality of types of components having different pitch intervals are mixed, by using a stencil method. In addition, it is an object of the present invention to provide a squeegee unit that can prevent defective solder supply from occurring and also prevent defective soldering and a method of using the squeegee unit.

[0010]

According to the present invention, an object of the present invention is to provide a squeegee unit for supplying cream solder to a pad of a printed wiring board by a stencil method. This is achieved by a squeegee unit having a plate and having a squeegee fin edge portion on one side higher than the other squeegee fin edge portion.

Further, according to the present invention, there is provided a method of supplying cream solder using the above-mentioned squeegee unit, wherein the squeegee fin on the side of which the edge portion is formed higher among the two squeegee fins is located in the advancing direction of the squeegee unit. It is achieved by a method for supplying cream solder, characterized in that the cream solder is supplied.

[0012]

[Function] The squeegee fin located on the side of the traveling direction has a high pressing force to supply cream solder to each opening with a strong pressing force, and then the second squeegee fin is suitable for the opening where cream solder scooping has occurred. Supply cream solder up to the amount.

[0013]

1 is a perspective view showing a squeegee unit according to an embodiment of the present invention, and FIG. 2 is a side sectional view showing a work flow of a cream solder supplying method using the squeegee unit over time.

Reference numeral 1 is a squeegee unit, and 2 is a squeegee fin. The squeegee fins 2 are each made of a material made of engineering plastic having elasticity, and the squeegee fin 2a on the left side of the two squeegee fins 2 is the leading side during the cream solder supply operation. The edge portion 3 of the squeegee fin 2 is formed in a spatula shape so that the edge portion 3 is easily bent and the area in contact with the metal mask is reduced.
It is easy to draw and apply cream solder.

Edge portions 3 of the squeegee fins 2a and 2b
The heights of a and 3b are different from each other, and the difference is about 3 mm in the present embodiment, but it is necessary to change the height by changing fins or the like depending on the situation of the target printed wiring board. Of course there is.

Since it is necessary to provide a desired space between the squeegee fins 2a and 2b in consideration of the bending of the squeegee fins 2a and the amount of cream solder carried by the squeegee fins 2b, a handle at the time of working with the spacer 4 interposed therebetween. The squeegee unit 1 is assembled by fixing and fixing the screws 5 so as to be sandwiched from above the two squeegee fins by the gripping portion 6 which becomes.

Next, a cream solder supply method using the squeegee unit 1 will be described. In this case, since the pressing force of the squeegee unit is set to be stronger in accordance with the narrow-pitch openings, the cream solder 13 can be sufficiently supplied to the narrow-pitch openings 14 without any problem. The problem is that the squeegee fins 2a go into the wide-pitch holes 15 too much, which causes the cream solder to gouge. However, as shown in FIG. In FIG. 2D, the cream solder carried by the squeegee fin 2b is replenished, and at the same time as the replenishment, excess solder is also cut off and the squeegee unit 1 passes. In the present embodiment, the squeegee fins 2b are different in height from each other by 3 mm lower than the squeegee fins 2a. Therefore, the pressing force of the edge portion 3b contacting the metal mask is also low, and the wide pitch opening portion 15 is formed. There is no such thing as going deep into. Also, of course, the narrow pitch opening portion 14
Has no effect on.

[0018]

As described above, the present invention is a squeegee unit having two squeegee fins having desired heights and different heights. Therefore, a narrow-pitch component and a wide-pitch component are mounted on a printed wiring board. Also, since it is not necessary to supply the cream solder in two steps by changing the pressing force, it is possible to improve the supply reliability.

In addition, a desired interval is provided and the heights are different.
Since cream solder is supplied using a squeegee unit that has a single squeegee fin, it is sufficient to handle mixed printed wiring boards with narrow-pitch components and wide-pitch components in a single operation. The cream solder can be supplied to the wiring board, soldering defects are less likely to occur, and the supply reliability is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a method of using the squeegee unit of the present invention.

FIG. 3 is a diagram showing a cream solder supply situation when a conventional squeegee unit is used.

FIG. 4 is a diagram showing a cream solder supply situation when a conventional squeegee unit is used.

[Explanation of symbols]

1 ... Squeegee unit, 2 ... Squeegee fin, 10 ... Printed wiring board, 11 ... Metal mask, 12 ... Pad, 1
3 ... Cream solder, 14 ... Narrow pitch opening, 15 ... Wide pitch opening

Claims (2)

[Claims] 1. A squeegee unit used for supplying cream solder to a pad of a printed wiring board by a stencil method, having two squeegee fins arranged so as to overlap with each other with a desired gap, and one side of the squeegee fin. A squeegee unit having an edge portion higher than the other squeegee fin edge portion. 2. A method of supplying cream solder using the squeegee unit according to claim 1, wherein, of the two squeegee fins, the squeegee fin on the side having a higher edge portion is set to the advancing direction side of the squeegee unit. A method for supplying cream solder, comprising supplying cream solder.