JPH02241081A - Manufacture of printed board - Google Patents

Abstract

PURPOSE:To produce a normal eutectic solder for settling the problem of hardly melting solder during the part mounting process by a method wherein a tin plated layer is formed on solder layers exposed to the printed board after formation of photosolder resist developed by alkali developer. CONSTITUTION:Solder layers as etching resist are formed and conductor patterns 5 are formed; the solder layers 6 on the conductor patterns are fused; and then solder resist patterns 8 are developed by bonding dry films thereon or coating a sensitizing solution thereon. At this time, an alkali developer is used so as to make the tin contained in the solder layers 6 melt in the developer for making the surface lead-rich. Next, the non-electrolytic tin plating process is performed on such a lead-rich solder layers 6 using a solution mainly comprising stannous chloride so as to form tin layers 7. This non-electrolytic tin plating process is performed up to the thickness of 0.5-1mum in order to complement the tin melted in the alkali developer. Later, an eutectic solder can be produced by remelting the solder.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for manufacturing a printed circuit board with fuser specifications, and the present invention provides a method for converting a solder layer whose composition ratio deviates from the eutectic ratio by developing a solder resist into a normal eutectic solder. For this purpose, a tin plating layer was formed on the solder layer exposed on the substrate surface on which a photo solder resist pattern was formed, and then the solder was remelted.

[Industrial application field]

The present invention relates to a method for manufacturing a printed circuit board, and particularly to a method for manufacturing a printed circuit board with fusing specifications.

[Prior art]

Printed circuit boards are soldered to improve the solderability of mounted components and the corrosion resistance of exposed conductor patterns.

There are two types of soldering process: one for fusing specification boards and one for solder coat specification boards, and the processes for each are slightly different.

FIG. 2 shows the manufacturing process of a printed circuit board of a fusing specification board to which the present invention is applied.

After drilling holes such as through holes, panel plating is applied,
Thereafter, so-called image processing is performed on the surface layer using a dry film or the like to form a menki resist layer 4 in areas other than the planned surface conductor pattern area (step 511).
).

Thereafter, a conductor pattern portion 5'' is formed by electrolytic plating (step 512), and a solder layer 6 is formed by electrolytic solder plating on the conductor pattern portion 5'' as an etching resist for the etching process described below (step 513). . Thereafter, the plating resist 4 such as the dry film is peeled off (step 514), and the lower layer conductor 2 other than the surface conductor pattern portion 5'' is etched to form the surface conductor pattern 5 (step 515).
).

Since the solder layer 6 is formed by electrolytic solder plating, it is porous and the surface is roughened by the etching process, resulting in poor adhesion of solder resist in subsequent steps. Thereafter, the solder layer 6 is fused (step 516) because it is necessary to coat the side surfaces of the conductive pattern 5 with solder as well.

If the printed circuit board 1 coated with solder is applied as it is to the component mounting process, there is a risk that the solder will melt and short circuit between each wiring.
Step 517), followed by contour processing.

[Problem to be solved by the invention]

In the manufacturing process of the above-mentioned fusing specification board, when coating the solder resist pattern 8, the accuracy of the solder resist pattern 8 has become a problem in recent years, and dry film or liquid coating has been used instead of the traditional printing method. Photosensitizers are now being used. However, if this dry film or the like is of a type that is developed with an alkaline developer, tin in the solder dissolves into the developer and the surface of the solder layer 6 becomes lead-rich.

Therefore, this solder layer 6 is no longer a eutectic solder, and its melting point (
The temperature rises (183°C) with eutectic solder, which poses a problem in that temperature control during component mounting is inconvenient.

The present invention has been proposed in view of the above-mentioned conventional circumstances. During the manufacturing process of printed circuit boards with fusing specifications, a solder layer whose composition ratio deviates from the eutectic ratio due to solder resist development is converted into normal eutectic solder. The purpose is to provide a method to do so.

[Means to solve the problem]

In order to achieve the above object, the present invention includes, for example, a printed circuit board with fusing specifications, as shown in FIG.
A tin plating layer 7 is formed on the solder layer 6 exposed on the substrate surface after a photo solder resist 8 developed with an alkaline developer is formed, and the solder is then remelted.

[For production]

By the above method, the newly plated tin layer 7 and the lead-rich lower solder layer 4 are mixed by melting to form eutectic solder.

〔Example〕

FIG. 1 is a process diagram showing one embodiment of the present invention. A conductor pattern 5 is formed by forming a solder layer 6 as an etching resist, and then the solder layer 6 on the surface of the conductor pattern 5 is fused (step S1), and then a dry film is pasted or The process up to the step of applying the liquid photosensitive agent and developing the solder resist pattern 8 (step S2) is the same as the conventional process. At this time, as mentioned above, an alkaline developer is used, so
The tin in the solder layer 6 is dissolved into the developer, and the surface becomes lead-rich. Electroless tin plating is applied to such a lead-rich solder layer 6 using a solution containing stannous chloride as a main component.
A tin layer 7 is formed (step S3). This electroless tin plating has a thickness of about 0.5 to 1 μm in order to compensate for the tin dissolved into the alkaline developer during the development step (step S2). After this, the solder is remelted (step S4)
Thus, eutectic solder is obtained.

After this, the external shape processing is performed as in the conventional case.

〔Effect of the invention〕

As described above, the present invention makes it possible to use normal eutectic solder for the solder on a printed circuit board, solving the problem of the solder being difficult to melt during component mounting, and facilitating temperature control.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the procedure of the present invention, and FIG. 2 is a process diagram showing the manufacturing procedure of a conventional solder resist specification. In the figure, 6...Solder layer, 7...Tin plating layer, 8...
...Photo solder resist pattern. Etching process diagram of an embodiment of the present invention 111

Claims (1)

[Claims] A tin plating layer (7) is formed on the solder layer (6) exposed on the substrate surface on which a photo solder resist pattern (8) developed with an alkaline developer is formed, and then the solder is remelted. Features of printed circuit board manufacturing method.