JPH03230596A - Method of mounting surface mounting type part - Google Patents

Abstract

PURPOSE:To remove a defective soldering between a lead terminal and a foot print by absorbing the whole effect of a variation in the amount of a solder in end portions. CONSTITUTION:Dummy pads 6 are provided in parallel outside both ends of the outside one of foot prints 5 which are arranged on the same row and connected to the lead terminals 3 of a package 2. a cream solder 7 is line-wise applied from the dummy pad 6 on one end to that on the other end via the foot prints 5 on the same row by the constant speed scanning of a continuous quantitative discharge nozzle to apply a reflow soldering to the package 2. That is, when the cream solder 7 is applied with the dummy pads 6 arranged outside both end foot prints 5 as a starting point and an end point, a variation in the amount of the solder due to the variation in positions in starting and end point portions is wholly absorbed by the dummy pads 6. thus, even the end foot prints 5 are not affected by the variation and a defective soldering due to the variation in the amount of the solder is not generated.

Description

[Detailed description of the invention] [Summary] Surface-mounted flat package components (hereinafter referred to as SM
D; 5 surface mount device) is mounted on a printed circuit board by applying cream solder with constant speed scanning of a continuous metered discharge nozzle, and then soldering the package with heat beam irradiation using reflow soldering. The purpose of this paper is to provide a method for mounting SMDs that reduces poor soldering between lead terminals and footprints without reducing work efficiency (i.e., printing SMDs in surface-mounted, flat-type packages). To mount it on a board, dummy pads are placed in parallel on the outside of both ends of the footprint in the same row that connects to the lead terminal of the package, and from the dummy pad at one end, the footprint is passed through the footprint in the same row, and then the dummy pad is connected to the dummy pad at the other end. up to,
The package is configured to be reflow soldered by applying cream solder in a line shape by scanning at a constant speed with a continuous quantitative discharge nozzle.

[Industrial application field]

In the present invention, in order to mount an SMD on a printed board, cream solder is applied by constant speed scanning of a continuous metered discharge nozzle.
SMD installation involves reflow soldering the package.

Reflow soldering is generally used to connect SMDs, which are surface-mounted components, to wiring patterns on printed circuit boards.

There are two methods of this reflow method: one is to gradually heat the entire device and weld the solder all at once, and the other is to heat only the parts and solder them.The former method allows you to solder a large number of SMDs at the same time. However, it has the disadvantage of requiring a long high-temperature heating time, and the latter requires only short-time local heating, and the heat resistance of SMD may be low, but it is not suitable for soldering many pieces at once due to local heating. .

Therefore, it is necessary to select a soldering method depending on the package structure and heat resistance of the SMD, the type of components mounted on the printed board, and the mounting surface.

[Conventional technology]

FIG. 2 shows an installation configuration diagram of a conventional example of a QFP type SMD.

SOP (Smal I Outline P) is used for surface mount type packages with flat terminal shapes.
ackage)/VSOP(Very 5OP)/QF
P(Quad Flat Pack-age)/VQ
F P (Very QFP) / S Q F P (S
A QFP type SMD is used as an example.

As shown in FIG. 2, a QFP type SMDI is a square package 2 with a large number of lead terminals 3 arranged in a row on each side.

A footprint 5 is provided on the printed board 45 to be connected to the lead terminal 3 at the mounting position of the SMD I.

For soldering, apply a predetermined amount of cream solder 7 to the footprint 5, and then connect the lead terminal 3 from the footprint 5.
Place the SMDI accurately so that it does not protrude, and perform reflow soldering.

However, with the miniaturization of SMDI, the footprint 5 has also become smaller and more densely arranged, and it has become increasingly difficult to apply the cream solder 7 accurately to only the footprint 5 using a metal mask, etc. ( In this conventional example, as shown in FIG. 2, a method is used in which cream solder 7 is applied in a line by scanning the rows of footprints 5 using a continuous metered discharge nozzle. When the lead terminal 3 is placed on top and heated, the cream solder 7 is melted and cut into lines or pieces, which are welded and soldered to the footprint 5 and the lead terminal 3.

[Problem to be solved by the invention]

However, (1) As the speed of applying the cream solder 7 increases, the positions of the starting point and the ending point become relatively inconsistent.

■ For this reason, the applied length of the cream solder 7 that protrudes outside the footprints 5 at both ends (dimensions shown in the figure) varies, causing variations in the amount of solder for the footprints 5 at both ends, and if there is too much solder, it may be applied to the adjacent footprints. 5 and the solder short-circuits, and if there is too little, unsoldered portions will occur, resulting in defective soldering.

■ For this reason, soldering required a lot of man-hours, such as testing to ensure defect detection and reworking defective parts.

There were problems such as.

In view of these problems, it is an object of the present invention to provide an SMD mounting method that reduces defective soldering between lead terminals and footprints without reducing work efficiency.

[Means to solve the problem]

As shown in FIG. 1, the above-mentioned problem is that when mounting the SMDI of the surface-mount flat package 2 on the printed circuit board 4, both ends of the footprint 5 in the same row connected to the lead terminal 3 of the package 2 must be placed on the outside. The dummy pads 6 are arranged in parallel, and from the dummy pad 6 at one end,
According to the present invention, the package 2 is reflow soldered by applying cream solder 7 in a line through the footprint 5 in the same row to the dummy pad 6 at the other end by scanning at a constant speed with a continuous metered discharge nozzle. The mounting of surface mount components is solved by the method.

[For production]

That is, if the cream solder 7 is applied using the dummy pads 6 arranged in parallel on the outside of the footprint 5 at both ends as the starting and ending points, all the variations in the amount of solder due to the positional variations at the starting point and the ending point will be completely absorbed by the dummy pads. 6, even the footprint 5 at the end is not affected by variations, and defective soldering due to variations in the amount of cream solder does not occur.

Incidentally, even if a solder short circuit occurs between the dummy pad 6 and the adjacent footprint 5 in the case of an excessive number, there is no problem as long as the dummy pad 6 is not connected to the printed wiring.

In this way, it is possible to provide an SMD mounting method that eliminates defective soldering between the lead terminal and the footprint and reduces inspection and rework man-hours.

〔Example〕

The present invention will be specifically described below with reference to embodiments shown in the drawings. The same reference numerals indicate the same objects throughout the figures. Figure 1 (
Figure a) shows a configuration diagram of an embodiment of the present invention, and figure (b) shows an enlarged view of the soldering state before soldering.

In this embodiment, the SMDI in a surface-mounted flat QFP package 2 is reflow soldered to a printed circuit board 4, which is the same as in the conventional example described above.

As shown in Fig. 1(a), the QFP type SMDI is a square package 2 with lead terminals 3 arranged around it at 0.51 mm.
It is a high-density package type in which a large number of them are arranged in a line at a mm pitch.

On the printed board 4, a footprint 5 with a width of 0.25 mm and a length of 1.8 mm is formed, corresponding to each lead terminal 3 of the SMDI, which is slightly thicker than the area where the tip of the terminal contacts flatly, and is used for wiring connection. This is done by a wiring pattern, and is further connected to other layers by vias 51 and through holes 52 provided at predetermined positions. Of course, the via 5 and the through hole 52 are provided outside the footprint 5.

Furthermore, dummy pads 6 having the same shape as the footprints 5 are arranged in parallel at the same intervals on the outside of the footprints 5 at both ends of the - row,
Wiring connections are left unconnected.

The cream solder 7 is applied as shown in FIG. 1(b).
Since the footprint 5 is miniaturized and arranged in a high-density manner, coating using a mask becomes inefficient, and a line-shaped coating method using constant-speed scanning of a continuous quantitative discharge nozzle (not shown) is used.

This coating is applied in a line from the dummy pad 6 at the end of the - row, passing through the footprint 5, to the dummy pad 6 at the other end.

This allows for variations in the starting and ending positions of coating (
However, as explained in the [Function] section above, the effects of variations in the amount of solder at the ends are all absorbed by the dummy pads 6.

After applying this cream solder 7, the SMDI is accurately placed so that the lead terminal 3 does not protrude from the footprint 5, and reflow soldering is immediately performed.

In this example, reflow soldering is performed by a partial heating method using a heating beam using a xenon lamp, and the lead terminals 3 are irradiated and soldered in accordance with the terminal rows on each side, and solder is welded on each side. Irradiation is repeated to complete the mounting of each SMDI.

The above embodiment is just an example, and SMDI is not limited to QFP type, but also VQFP/5QF with lead terminals 3 provided at a higher density.
SOP/V with P type or dual flat terminal arrangement
There is no problem with the SOP type, but the key point is to install dummy pads 6 on the outside of both ends of the footprints 5 in the same row, apply cream solder 7 in a line to each row, and reflow solder the SMD. However, the dimensions, the shape of the dummy pads 7, and the installation intervals are not limited to these.

〔Effect of the invention〕

(Thus, it becomes possible to provide a method for installing 5h=ID.

As described above, the SMD mounting method of the present invention eliminates defective soldering between lead terminals and footprints, reduces inspection and rework man-hours, and improves work efficiency with soldering. Quality can also be improved, and the resulting economic effects can be significant.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, and FIG. 2 is an installation configuration diagram of a conventional example of a QFP type SMD. In the figure, l is SMD, 2 is package, 3 is lead terminal, 4.45 is printed board, 5 is footprint,
6 is a dummy pad, 7 is cream solder, 51 is a via, and 52 is a through hole.

Claims (1)

[Claims] Components (1) of a surface-mounted flat package (2)
) to mount the package (
Dummy pads (6) are installed in parallel on the outside of both ends of the footprint (5) in the same row that connects to the lead terminal (3) of 2), and from the dummy pad (6) at one end, the footprint ( 5) to the dummy pad (6) at the other end, apply cream solder (7) in a line shape by scanning at a constant speed with a continuous metered discharge nozzle.
) is a method for attaching surface-mounted components, characterized by reflow soldering.