JPH0258294A - Method for fitting surface mounting parts on printed wiring board - Google Patents

Abstract

PURPOSE:To improve the wettability of soldering in the course of reflow soldering so that no inferior soldered part can be produced and necessity of manual modifying works can be eliminated by making the extent to which paste-like cream solder to be applied to a printed wiring board is applied larger than the pad to which surface mounting parts are fitted. CONSTITUTION:In the course of fitting surface mounting parts 6 to a printed wiring board 5 by reflow soldering, the extent 9 to which paste-like solder to be applied to the board 5 is applied is set larger than the pad 1 to which the surface mounting parts 6 are fitted. For example, the part of the cream solder which spreads to the outside of the chip parts fitting pad at the cream soldering time flows to the electrode of chip parts by the surface tension of the molten solder and the surface tension of the contained flux at the reflow soldering time. Therefore, the oversize of the cream solder to the fitting pad 1 is freely set in accordance with the size of the chip parts 6 to be mounted, that is, the size of the electrode 7 by utilizing the action, so that the cream solder can be applied in an appropriate applying size 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to the application range of cream solder when attaching surface mount components to a printed wiring board by reflow soldering.

[Conventional technology]

4 and 5 are plan views showing the relationship between the cream solder application size and the chip component mounting pad size when attaching chip components to a conventional printed wiring board using the reflow soldering method. The figure shows a case where the cream solder application size is narrower than the chip component mounting pad size (so-called small size cream solder), and Figure 5 shows the case where the chip component mounting pad size and the cream solder application size are the same. It shows. FIG. 6 is a side view of the conventional chip component mounting pad size shown in FIGS. 4 and 5 after applying cream solder and performing flow soldering. In the figure, 1 is a chip component mounting pad;
2 is a conductive pattern, 3 in FIG. 4 is a small size cream solder for the chip component mounting pad 1, and 4 in FIG. 5 is a cream solder of the same size for the chip component mounting pad 1. In addition, 5 in Fig. 6 is a printed wiring board,
6 is a chip component, 7 is a chip component with 4 poles, and 8 is a soldering state after flow soldering using conventional cream solder size.

In the above-mentioned conventional technology, by using small-sized cream solder 3 or cream solder 4 of the same size for the chip component mounting pad 1, the mounting pitch of the chip component 6 in the parallel direction with respect to T4Ili7 is as follows. It is determined by the size of the chip component mounting pad 1.

[Problem to be solved by the invention]

With conventional cream solder sizes for conventional chip component mounting pads, the amount of cream solder for the electrodes of large square chip components is insufficient, so the solder does not cover the entire electrode of the chip component, resulting in poor soldering. ,
After reflow soldering, it is necessary to add solder manually. However, due to reheating caused by such work,
There were problems such as reliability of chip parts and deterioration of quality of soldering parts.

This invention was made to solve the above-mentioned problems, and aims to eliminate soldering defects and eliminate manual correction work by improving the solder surroundings in reflow soldering. do.

[Means for Solving the Problems] The method for attaching surface mount components to a printed wiring board according to the present invention is as follows:
When the chip component mounting pad size is 81 and the cream solder application size is 32, the cream solder applied to the chip component mounting pad is oversized as shown in 32)81.

[Effect]

In this invention, since the size of the cream solder for the chip component mounting pad is oversized, the solder to the II of the chip component can be spread well, and soldering defects can be eliminated.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a chip component mounting pad, 2 is a conductive pattern, 9 is the state after applying cream solder, and in FIG. 2, 5 is a printed wiring board, 6 is a chip component, and 7
10 is the electrode of the chip component, and 10 is the state of soldering after cream soldering or flow soldering.

Next, the effect will be explained. When applying cream solder,
The part of the cream solder that overlaps the chip component mounting pad may melt during reflow soldering and flow to the electrode of the chip component due to the surface tension of the solder and the surface tension of the flux it contains. It is.

Utilizing the above effect, the oversize of the cream solder on the pad can be freely set according to the size of the chip component to be mounted, that is, the size of the electrode, and the cream solder is always applied at an appropriate size. It is.

In the above embodiment, one direction of the cream solder 9 over the chip component mounting pad 1 is the direction toward the electrode surface 7 of the chip component, but it may be provided in the width direction of the chip component 6.

Further, in the above embodiment, the case of a square chip component was explained, but as shown in FIG. 3, other surface mount components such as SOP, QFP, surface mount type resistor, etc. The same effects as in the above embodiment are achieved.

That is, in FIG. 3, 11 is a sop or QFP mounting pad, and 12 is a sop or 1! QFP This is the cream solder size for the P mounting pad.

〔Effect of the invention〕

As described above, according to the present invention, the size of the cream solder to be applied can be freely set depending on the size of the component to be mounted, the electrode area, the lead shape, etc., and by applying an appropriate amount of cream solder, soldering can be performed. Defects and their rework can be eliminated, and optimal soldering conditions can always be obtained. In addition, soldering prevents a decrease in the reliability of parts due to reheating during repair and a decrease in the quality of soldering parts. Also, in flow soldering for mixed boards such as SOP and QFP, cream is used to prevent solder bridges. It also has the effect of ensuring an appropriate amount of solder even if the solder thickness is reduced.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the relationship between a chip component mounting pad and cream solder application according to an embodiment of the present invention, FIG. 2 is a side view of the final state in which the present invention is implemented, and FIG. 4 and 5 are plan views showing the relationship between the conventional chip component mounting pad and cream solder application. FIG. 6 is a plan view showing the relationship between the conventional chip component mounting pad and cream solder application. FIG. 6 is a side view of the final state shown. In the figure, 1 is a chip component mounting pad, 2 is a conductor pattern,
5 is a printed wiring board, 6 is a chip component, 7 is 1 m long, 9 is cream solder size, and 10 is solder. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] When soldering surface mount components to a printed wiring board using the reflow soldering method, the application area of paste-like cream solder applied to the printed wiring board is set to be larger than the pad on which the surface mount component is attached. A method for attaching surface mount components to printed wiring boards.