JP2001244616A - Metal mask for printing cream solder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a careless adherence of a cream solder to connecting terminals of a circuit board to be printed. SOLUTION: A metal mask 10 for printing the cream solder used in the case of printing the cream solder on a solder land comprises the land formed at a predetermined position and disposed on the circuit board 2 to be printed having connecting terminals 4a, 4b connected to another circuit components. In this case, recesses 11 not contacted with the terminals are formed on a surface opposed to the terminals 4a, 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cream solder printing metal mask, and more particularly, to a cream solder printing metal mask that prevents careless solder from adhering to connection terminals of a circuit board to be printed. It relates to a metal mask.

[0002]

2. Description of the Related Art According to a reflow soldering method, cream solder is printed (applied) on solder lands of a circuit board in advance.
Is done. Then, after mounting the chip component thereon, soldering is performed in a heating atmosphere. In many cases, a metal mask is used for printing the cream solder, and an example thereof will be described with reference to FIG.

In this example, the printed circuit board 2 may be either a hard board or a flexible board. Although not shown, solder lands are formed at predetermined positions on the printed circuit board 2. . Also, the printed circuit board 2
Is mounted with a chip component 3 such as an LSI in advance, and, for example, an input terminal 4a and an output terminal 4b connected to another circuit component (circuit board) at an end of the board.
Are provided. The input terminal 4a and the output terminal 4
When it is not necessary to distinguish between b and b, these are collectively referred to as connection terminal portions 4.

The metal mask 1 is formed of a metal plate having a shape larger than that of the circuit board 2 to be printed, on which a perforated pattern 1a corresponding to a solder land of the circuit board 2 to be printed is formed. The metal mask 1 has chip components 3
(A concave portion when viewed from the printed circuit board 2 side) 1b is provided for allowing the air to escape. The other surface is a flat surface that is in close contact with the substrate surface of the printed circuit board 2.

The metal mask 1 is pressed by a jig (not shown) so as to be in close contact with the printed circuit board 2.
A cream solder 5 as an ink material is supplied thereon.
Then, by rubbing the metal mask 1 with the squeegee 6, the cream solder 5 is printed on each solder land of the printed circuit board 2 through the perforated pattern 1a.

[0006]

The printing of the cream solder 5 is performed as described above. However, since the cream solder 5 is made of a viscous mixture of solder particles and flux, the metal mask 1 is covered after printing. Printed circuit board 2
When the metal mask 1 is separated from the metal mask 1, the solder wraps around the back surface of the metal mask 1 and is gradually deposited no matter how good the mask is at present. As a result, the quality of solder printing deteriorates, and in extreme cases, solder balls may be generated after reflow.

In order to prevent this, the back surface of the metal mask 1 is periodically cleaned. However,
When attempting to remove the cream solder from the back surface of the metal mask 1 by this cleaning, the cream solder may adhere to the surface of the printed circuit board 2 facing the connection terminal portion 4 for some reason.

[0008] Then, in the printing after cleaning, the cream solder adheres also to the connection terminals 4 of the printed circuit board 2, and when connecting other circuit components to the connection terminals 4, the adhesion flux is applied. This leads to poor connection and reduced adhesive strength, and short-circuit failure caused by solder particles straddling between the terminal electrodes.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made to solve such a problem, and its structural feature is that a solder land is formed at a predetermined position,
A cream solder printing metal mask arranged on a printed circuit board having a connection terminal connected to another circuit component and used when printing cream solder on the solder land, facing the connection terminal. The surface is provided with a concave portion that is not in contact with the connection terminal portion.

According to this structure, the surface of the circuit board to be printed facing the connection terminal portion is cleaned with the cleaning of the metal mask.
Even if the cream solder adheres, there is no possibility that the cream solder adheres to the connection terminal portion of the printed circuit board. In addition, since the particle size of the solder is generally 50 μm or less, the depth of the recess is preferably 0.1 mm or more.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment (example) of the present invention will be described with reference to FIGS. 1 and 2. The printed circuit board 2 will be described with reference to FIG. The same one as in the conventional example is used.

That is, the printed circuit board 2 is a hard board,
Although it may be any of flexible boards, and not shown, solder lands are formed at predetermined locations on the printed circuit board 2. The printed circuit board 2 has L
Although chip components 3 such as SI are mounted in advance, in the present invention, the chip components 3 are optional components.

Further, at the end of the printed circuit board 2,
An input terminal 4a and an output terminal 4b connected to another circuit component (circuit board) are provided. Although not shown, each of these terminal portions (connection terminal portion 4) is provided with, for example, strip-shaped connection electrodes at predetermined intervals. Note that the connection terminal section 4 does not necessarily need to be provided at the end of the board, and may be provided at an arbitrary position on the printed circuit board 2.

The metal mask 10 in this embodiment is also
Like the metal mask 1 described above, the metal mask is made of a metal plate formed larger than the printed circuit board 2, and a perforated pattern 1 a corresponding to the solder land of the printed circuit board 2 is formed on the metal plate. In addition, the metal mask 10 is provided with a convex portion 1b for allowing the chip component 3 to escape.

The difference between the metal mask 10 and the conventional metal mask 1 is that the metal mask 10
Input terminal 4a and output terminal 4b of printed circuit board 2
The point that the concave portions 11 and 11 that are not in contact with the connection terminal portion 4 are formed on the surface facing the (connection terminal portion 4).

As shown in the enlarged sectional view of FIG. 2, in this embodiment, the concave portion 11 is
Are pressed from the back side (the printed circuit board 2 side) to the front side. Therefore, on the surface side of the metal mask 10, the concave portion 11 is a convex portion.

The depth of the recess 11 is determined by the cream solder 5 (FIG. 3).
The particle size of the solder contained in the solder is generally 50 μm.
Since it is the following, it is preferable that it is 0.1 mm or more. Note that, depending on the thickness of the metal mask 10, the recess 11 may be formed by, for example, half etching.

As another method, the metal mask 10 can be manufactured by a plating method. That is, a plating layer is laminated a plurality of times in a molding die in which a portion corresponding to the connection terminal portion 4 is a convex portion,
By taking it out of the molding die, the metal mask 1
0 may be obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the conventional metal mask 1 described with reference to FIG.
, The printed circuit board (multi-board; multi-board) 1
Cream solder 5 was printed on 000 sheets. At this time, the back side of the metal mask 1 was cleaned every 25 printings. As a result, the failure rate due to the adhesion of the cream solder to the connection terminal portion 4 was 43/1000.

With the metal mask 10 according to the present invention, a printed circuit board (multi-substrate;
Cream solder 5 was printed on 1000 sheets of a multi-faced substrate. As a result, the failure rate due to the adhesion of the cream solder to the connection terminal portion 4 was 0/1000.

[0021]

As described above, according to the present invention,
Cream solder printing, which has solder lands formed at predetermined locations and is arranged on a printed circuit board having connection terminals connected to other circuit components, and is used when printing cream solder on the solder lands. In the metal mask for use, by forming a concave portion that is not in contact with the connection terminal portion on the surface facing the connection terminal portion, the surface facing the connection terminal portion of the printed circuit board with the cleaning of the metal mask. Even if the cream solder adheres, the cream solder does not adhere to the connection terminal of the printed circuit board, and the connection terminal of the printed circuit board can be effectively protected.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a metal mask according to an embodiment of the present invention is combined with a printed circuit board.

FIG. 2 is an enlarged sectional view of a main part of the embodiment.

FIG. 3 is a cross-sectional view showing a conventional metal mask together with a printed circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal mask 1a Perforated pattern 11 Concave part 2 Printed circuit board 3 Chip component 4 Connection terminal part 4a Input terminal 4b Output terminal

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B41N 1/24 B41N 1/24 H05K 3/12 610 H05K 3/12 610P // B23K 101: 42 B23K 101: 42 F term (Reference) 2C035 AA06 FD01 FD39 FF22 FF26 2H114 AB12 AB13 AB15 AB17 EA04 5E319 AC01 BB05 CD07 CD29 5E343 AA02 BB54 BB72 FF14

Claims (2)

[Claims] When solder cream is printed on a solder land, the solder land is formed on a predetermined circuit board and has a connection terminal connected to another circuit component. A metal mask for cream solder printing, wherein a concave portion that is not in contact with the connection terminal portion is formed on a surface facing the connection terminal portion. 2. The cream solder printing metal mask according to claim 1, wherein the depth of the recess is 0.1 mm or more.