JP2605497Y2 - Printed wiring board for surface mounting - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board for surface mounting which facilitates inspection of a solder joint when electronic components or the like are surface mounted on the printed wiring board.

[0002]

2. Description of the Related Art As electronic devices have become smaller and lighter and have higher performance, electronic components have become lighter, thinner and shorter, and high-density packaging technology has made remarkable progress. In particular, the integration density of a semiconductor high-density large-scale integrated circuit (hereinafter, referred to as “ULSI”) is remarkably improved, and the ULSI is moduled in a small package, and many connection lead pins are attached. For example, an SM-PGA (Surface Mou)
(nt Type Pin Grid Array) There is molded in the package, its size is 35mm × 35mm,
The number of lead pins is 441 or 368. The lead pins have a pitch of 1.27 mm and make a round around the periphery in five rows. This is mounted on a printed wiring board for surface mounting. In the mounting part of the printed wiring board,
A conductor pattern (copper foil) is formed in advance, and solder is applied thereon. When an SM-PGA package preliminarily soldered is placed on a lead pin and heated, the solder melts and is soldered. On the other hand, ULS
The operation of the electronic circuit such as I is accurate, and if there is even one solder defective place, the circuit does not operate normally and becomes a defective product. Therefore, usually, after soldering, the quality determination is always checked by visual inspection.

FIG. 2 shows a conventional inspection method after soldering of the SM-PGA package 1. The SM-PGA package 1 is soldered to a conductor pattern of a printed wiring board 4 via a lead pin 2 at a solder connection portion 3.
The distance between the SM-PGA package 1 and the printed wiring board 4 is about 1.5 mm, and 441 lead pins 2 are soldered here. In this state, visual inspection cannot be performed by a normal method. Then, SM-
The solder joint 3 on the lower surface of the PGA package 1 is reflected by a mirror 6 and peeped from above using a stereoscopic microscope 5 and magnified to judge the quality. However, SM-
The larger the vertical and horizontal dimensions of the PGA package 1 and the shorter the length of the lead pin 2,
The illumination light below the M-PGA package 1 is weakened, the illumination light is insufficient and the illumination becomes dark, and the inspection of the solder connection part 3 becomes difficult, and an inspection error occurs. In addition, such a package having insufficient illumination light includes SM-PGA.
In addition to the package 1, there are a J-lead package, an SOJ package, a PLCC package, and the like.

[0004]

[Problems to be solved by the invention] The invention is based on SM-PG
Provided is a printed circuit board for surface mounting which makes illumination light on the lower surface of the A package 1 or the like as bright as possible.

[0005]

In order to achieve the above-mentioned object, the present invention provides a printed circuit board under the SM-PGA package 1 which has a large irregular reflection of light within a range not affecting electric wiring. Print, apply or paste to make the reflected light relatively bright.

[0006]

FIG. 1A and FIG. 1 show an embodiment of the present invention.
(B) shows. FIG. 1A is a cross-sectional view, and FIG.
(B) is a top view. SM-PGA Package 1 is
The lead pin 2 goes around the periphery of the package in five rows of 441 pins. Therefore, there is a portion without a pin in the central portion 7. Using this portion, an object to which the illumination light is most likely to be irregularly reflected is printed or pasted.

FIGS. 1A and 1B show an example in which the lower central portion 7 of the SM-PGA package 1 of the printed circuit board is silk-printed with a solid white color. On the printed wiring board 4 for surface mounting, silk printing is usually performed in order to mark a component position and a component symbol. Therefore, adding the white solid silk printing does not increase the number of steps. Then, scattered light is generated by the unevenness of the printing surface, and the area below the SM-PGA package 1 becomes bright. In this state, when the visual inspection is carried out with the stereo microscope 5 from above using the mirror 6, it is possible to observe well.

In the processing of the printed circuit board 4 in the central portion 7 below the SM-PGA package 1, the same effect can be obtained not only in white solid silk printing but also in bright color silk printing. The most suitable paint may be used in relation to the silk printing such as the position of other parts.

As another method, there is a method in which a light-colored white tape or metal foil is attached. Further, when there is no wiring at the position of the central portion 7 below the SM-PGA package 1 due to the printed wiring, the same effect can be obtained by leaving the copper foil of the printed wiring board and plating.

[0010]

As described above, according to the present invention, in a printed wiring board on which electronic components, particularly, a semiconductor high-density large-scale integrated circuit such as the SM-PGA package 1 are surface-mounted, the components are surface-mounted and then soldered. Can be easily checked by visual inspection, defects can be found in advance, and manufacturing errors can be eliminated, and the effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram of one embodiment of the present invention.

FIG. 2 is a diagram of a conventional example.

[Explanation of symbols]

1 SM-PGA (Surface Mount Type Pin Grid Arra
y) Package 2 Lead pin 3 Solder joint 4 Printed wiring board 5 Stereo microscope 6 Mirror 7 Central part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 1/02 H05K 1/18 H05K 3/34 512

Claims (1)

(57) [Scope of request for utility model registration] (1) There is no lead pin at the center and multiple pins at the periphery.
When a printed circuit board on which electronic components having several rows of lead pins are mounted on the surface, the electronic components are mounted
The pudding facing the central part where the lead pins are not provided.
A printed wiring board for surface mounting, wherein an object that diffusely reflects light is attached to the surface of the wiring board.