JPH02180091A - Printing of paste on printed board - Google Patents

Abstract

PURPOSE:To print in accurate conformity with a paste holding hole by extruding paste held in the paste holding hole of a printed plate by the deformation of an elastic plate to print it on a printed board directly thereunder. CONSTITUTION:A printing plate 2 opened with a paste holding hole 21 corresponding to a printing position is disposed above a printed board 1 on which paste like cream solder or conductive adhesive is printed. In a printing step, paste 5 is first held in the paste holding hole 21 of the printing plate 2, and disposed on the printed board 1. In this case, the printing plate 2 is not brought into close contact with the upper face of the printed board 1, but desirably separated by a suitable micro distance delta. An elastic plate 3 is disposed on the upper face of the printing plate 2, the upper face of the elastic plate 3 is pressed by a pressing roller 4 to be swept over the whole surface of the printing plate 2. Thus, paste is printed in accurate conformity with the position of the paste holding hole 21 on the printed board 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for printing paste on a printed circuit board, and more specifically, a method for printing a paste such as cream solder or conductive adhesive at a desired position on a printed circuit board. This relates to a printing method for printing.

[Conventional technology]

When mounting chip components on a printed circuit board, a paste such as cream solder or conductive adhesive is printed and adhered to the land at the mounting position in advance, and after the component is mounted, it is heated and melted in a reflow oven. Methods of fixing parts are widely used.

In the above technique, as a method for printing paste on a printed circuit board, a screen printing method illustrated in FIG. 3 is conventionally used.

In this method, first, a stencil screen 102 with through holes 102A formed therein corresponding to the paste printing position on a printed circuit board I is prepared, and this is stretched over a rectangular formwork 105, and the stencil screen 102 is placed on a printed circuit board to be printed. Next, place the paste 104 on the top surface of the stencil screen IO'2, and spread it over the entire surface of the screen with an attack angle θ using the squeegee 103, passing the paste through the through hole 102A. 104 is attached and printed 104A on the printed circuit board 1.

[Problem to be solved by the invention]

In the conventional screen printing method, since the stencil screen 102 is thin enough to be flexible as shown in the figure, and the through holes 102A are formed mainly by etching, it is impossible to perform precise perforation with a fine pitch. The drawback was that high-density component mounting was not possible.

Furthermore, as the squeegee 103 moves, the contact point P between the stencil screen 102 and the printed circuit board is printed while moving one after another, so the printing accuracy depends on the size of the screen distance e and the attack of the squeegee 103. The paste 104A is easily influenced by the angle θ, and therefore the position of the paste 104A actually printed on the printed circuit board is slightly shifted from the position of the through hole 102A drilled in the stencil screen 102, which has the disadvantage that highly accurate component mounting is not possible. there were.

[Failure to solve the problem]

This invention was made to solve the above-mentioned problem, and includes a printing template having paste holding holes formed at positions where paste such as cream solder or conductive adhesive is to be attached and printed on a printed circuit board. a step of arranging the paste on the printed circuit board at a required minute distance with the paste held in the paste holding hole; a step of arranging an elastic plate in close contact with the printing template; and a step of disposing the elastic plate from above the elastic plate. The printing plate is pressed with a pressure roller and swept over the entire surface of the printing template.

[Effect]

The paste held in the paste holding holes of the printing template is pushed out by the deformation of the elastic plate and printed on the printed circuit board directly below. In this method, the printing template does not bend and is therefore made of a hard metal material of suitable thickness. The paste is printed in exact correspondence with the paste-retaining holes in the printing template.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

Above the printed circuit board on which a paste such as cream solder or conductive adhesive is to be printed, there is placed a printing template 2 having two paste holding holes perforated in correspondence with the printing positions.

In this invention, the printing template 2 does not need to be greatly curved unlike the stencil screen of the prior art.
For example, it is best to use a hard metal plate such as stainless steel with a thickness of about 0.3 mm to 1 mm, and the paste holding holes 21 are precisely drilled by pure mechanical processing such as drilling or pressing, or by electric discharge machining. be done.

An elastic plate 3 having an appropriate thickness is arranged on the upper surface of the printing template 2. The elastic plate 3 is, for example, a foam molded product with closed cells or open cells like a sponge, or a soft rubber molded product, and in layman's terms, if you pinch it with your fingers, the part will swell in three dimensions. It is a three-dimensionally elastically deformable plate that returns to its original planar state when released.

In the printing process according to the method of this invention, first, the paste 5 is held by the paste holder 21 of the printing template 2 and placed on the printed circuit board 1. At this time, the printing template 2 is the printed circuit board 1
without contacting the upper surface of the
．． It is best to keep them separated by about 1 to 0.8 ml11. The value of this minute distance δ is selected in accordance with the printing thickness of the paste. Then, an elastic plate 3 is arranged on the upper surface of this printing template 2.

After the above-mentioned preparation process, a suitable pressure roller 4 is placed on the printing template 2.
Press and roll so that it covers the entire surface. In this way, as shown in an enlarged view in FIG.
The paste 5 inside is deformed and inserted as shown in 1.
is pushed out directly below to print and adhere 5A onto the printed circuit board. In this way, the paste is printed on the printed circuit board 1 in exact correspondence with the positions of the paste holding holes 21.

〔effect〕

According to this invention, (1) the printing template is a hard metal plate with a certain thickness or more, and the paste holding holes are machined, making it possible to precisely drill holes with a fine pitch; This has the effect of allowing high-density component mounting. Furthermore, (2) for the above reasons, there is an advantage that the durability of the printing template is improved. Furthermore, (2) the amount of paste to be printed is determined approximately by the thickness of the printing template, so there is an advantage that a constant amount of paste can always be deposited on the printed circuit board.

[Brief explanation of the drawing]

Figure 1 is a simplified side sectional view showing the steps of the method of this invention;
The figure is an enlarged side sectional view of FIG. 1, and FIG. 3 is a side sectional view showing the prior art. DESCRIPTION OF SYMBOLS 1...Printed circuit board, 2...Printing template, 21...Paste holding hole, 3...Elastic plate, 4...Press roller. Applicant NEC Home Electronics Co., Ltd. Agent Patent Attorney Masu 1) Takeo

Claims (3)

[Claims] 1. Paste such as cream solder or conductive adhesive is attached to the printed circuit board. A printing template with paste holding holes is drilled at the position where the paste is to be printed. With the paste held in the paste holding holes, the printing template is placed on the printed circuit board as required. a step of arranging an elastic plate closely on the printing template; and a step of pressing a pressure roller from above the elastic plate to sweep it over the entire surface of the printing template. A paste printing method on a printed circuit board having 2. 2. The method of printing paste on a printed circuit board according to claim 1, wherein the elastic plate is a foam molded plate of synthetic resin. 3. 2. The method of printing paste on a printed circuit board according to claim 1, wherein the printing template is formed of a stainless steel plate.