JPS6216595A - Manufacture of printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] This is an improvement in the manufacturing method of a printed circuit board, in which an electroless copper plating layer and an electrolytic copper plating layer (usually a laminated layer of both) are used as a panel copper plating layer for pattern formation. After removing the resist pattern formed on the patterned copper plating layer, the solder plating layer formed on the patterned copper plating layer is melted prior to the step of etching away the panel copper plating layer and copper foil under this resist pattern. . This molten solder plating layer then covers the side surfaces of the patterned steel plating layer formed below to prevent side etching of the patterned steel plating layer below the solder plating layer, which will become the conductor layer pattern of the printed circuit board. .

And a method for manufacturing a printed circuit board in which the formed pattern is prevented from becoming thinner than a predetermined size.

[Industrial application field]

The present invention relates to an improvement in a method for manufacturing a printed circuit board, and in particular, after removing a resist pattern used for pattern formation,
In this process of etching away the unnecessary panel copper plating layer and copper foil under the resist pattern, the pattern copper plating layer under the solder plating layer for pattern formation is not etched, and the pattern to be formed has a predetermined size. This invention relates to a method of manufacturing a printed circuit board that does not become thinner.

Printed circuit boards on which electronic components such as ICs and LSIs are mounted to form electronic circuits are used in the manufacture of many electronic devices.

In order for the formed electronic circuit to have predetermined electrical characteristics, such printed circuit boards are required to have conductive layers such as solder plating layers that form the circuit pattern formed to predetermined design dimensions. There is.

[Conventional technology]

Among such printed circuit boards, a conventional method for manufacturing a multilayer laminated printed circuit board will be described.

As shown in FIG. 3, a copper foil IA is placed in a mold (not shown) of a pressurizing device, an adhesive sheet 2A made of a semi-hardening resin called prepreg, and a conductive layer on both sides of a glass epoxy resin plate 3. After laminating the intermediate layer 5 on which the circuit pattern 4 was formed, and further laminating the adhesive sheet 1-2B and the copper foil 1B on top of this in sequence, the mold was heated and pressurized so that the circuit pattern 4 of the intermediate layer 5 was made of resin. A laminated printed circuit board 6 embedded in the substrate is formed.

Furthermore, as shown in FIG. 4, conductive holes 7 are formed for connecting the circuit patterns 4 of the intermediate layer 5 and the patterns formed on the surface copper foils IA and 1B, and for connecting and installing electronic components. .

Next, as shown in FIG. 5, electroless copper plating layers 8 are formed on both surfaces of the printed circuit board 6 and on the inner walls of the conductive holes 7. This electroless copper plating can also deposit copper on the surface of the resin.

Further, an electrolytic copper plating layer 9 is formed on the electroless copper plating layer 8.

Next, as shown in FIG. 6, a film-like photoresist film (not shown) was attached to both sides of the printed circuit board on which the electrolytic copper plating layer 9 was formed, and this photoresist film was exposed to light using a mask with a predetermined pattern. Thereafter, the non-exposed portions are removed using a resist removal material to form predetermined resist patterns IO on both sides of the printed circuit board.

Further, as shown in FIG. 7, patterned copper plating is carried out using this resist pattern 10 as a mask, and patterned copper plating layer 11 is applied to the inner wall of the conductive hole 7 and the areas other than the resist pattern 1O formation locations on both sides of the printed circuit board. Further, a solder plating layer 12 is formed on the patterned copper plating layer 11 by electrolytic plating.

Furthermore, as shown in FIG. 8, the resist pattern 10 is removed using a resist removing liquid.

Furthermore, as shown in FIG. 9, using this solder plating layer 12 as a mask, the electrolytic copper plating layer is removed under the area where the resist pattern 10 was formed using an etching solution that dissolves copper but not the solder. 9. Etch and remove the electroless copper plating layer 8 and the copper foil 1B.

Further, the solder plating layer 12 described above is once melted and solidified. This process is a fusing process to improve solder flow when components are mounted on a printed circuit board and soldered.

(Problems to be Solved by the Invention) However, using an etching solution that dissolves the copper but does not dissolve the solder, the electrolytic copper plating layer 9 formed under the resist pattern 1° and the electroless copper When etching the plating layer 8 and the copper foil 1B, the etching solution wraps around and enters under the solder plating layer 12. Therefore, as shown in FIG. In addition, a phenomenon of side etching occurs in which the electrolytic copper plating layer 9, the electroless copper plating layer 8, and the copper foil 1B underneath are etched from the side surfaces, and as a result, the formed pattern becomes thinner than the predetermined size. This causes many problems.

Furthermore, an overhang phenomenon occurs in which the solder plating layer 12 protrudes on both sides, and in a later process, the overhanging solder falls off, resulting in a circuit short circuit.

Further, when foreign matter or the like adheres to the patterned copper plating layer 11 and that part is not solder plated, there is a problem that this part is etched away and the pattern forming layer 13 is chipped, resulting in pattern defects such as pinholes.

[Means for solving problems]

The present invention solves the above-mentioned problems, and removes the electrolytic copper plating layer 9, electroless copper plating layer 8 and copper foil 1B under the removed resist pattern 10 from the patterned copper plating layer 11.
Prior to etching and removing the solder plated layer 12 formed thereon as a mask, a step of melting the solder plated layer 12 is applied as shown in FIG. 2, and then,
Using the melted solder plating layer 12 as a mask, the electrolytic copper plating layer 9, the electrolytic copper plating layer 8, and the copper foil 1B are removed by etching.

[Effect]

According to the method of the present invention, since the solder plated layer 12 is melt-treated, the molten solder plated layer 12 is attached to the side surface of the patterned copper plated layer II forming the pattern forming layer 13. is the pattern forming layer 13
The patterned copper plating layer 11 will not be etched even if the patterned copper plating layer 11 is penetrated from the side surface, and the disadvantage that the formed pattern forming layer 13 will be thinner than the designed dimension can be eliminated.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

First, as shown in FIG. 1, the electroless copper plating layer 8 and the electrolytic copper plating layer 9 described above are formed on the substrate 6 on which the copper foil 1B is formed, and then a resist pattern 10 of a predetermined pattern is formed on the substrate 6. After forming, using this resist pattern 10 as a mask, a patterned copper plating layer 11 and a solder plating layer 12 are sequentially formed, and then the resist pattern 10 is removed. The steps up to this point are the same as the conventional steps. Next, a step of melting the solder plating layer 12 on the patterned copper plating layer 11 of the present invention is applied.

This step can be easily carried out by passing the □ printed circuit board 6 from which the resist pattern 10 has been removed through a heating furnace heated to a temperature of around 230°C.

Then, as shown in FIG. 1, the melted solder plating layer 12 covers the side surfaces of the patterned copper plating layer 11.

Furthermore, as shown in FIG. 2, this melted solder plating layer 1
2 as a mask, the electrolytic copper plating layer 9 and the electroless copper coating layer 8# were formed in the lower region of the resist pattern 10.
Then, the copper foil 1B is removed using an etching solution that melts only the copper without melting the solder.

In this way, the patterned copper plating layer 11 that forms the circuit pattern of the printed circuit board will not be side-etched, and the circuit pattern will not be formed thinner than the designed dimension, resulting in a highly reliable printed circuit board. is obtained.

Furthermore, the solder plating layer 12 protrudes from the side surface of the patterned copper plating layer 11 to form an overhanging single plating layer, and it is also possible to prevent the solder plating layer from falling onto the board and causing a short circuit in the circuit pattern.

Further, in the conventional method, when foreign matter adheres to the patterned copper plating layer 11 and the solder plating layer 12 does not adhere to the copper plating layer 11 due to the foreign matter, the solder plating layer 12
When etching the electrolytic copper plating layer 9 on the substrate using as a mask, part of the patterned copper plating layer 11 is etched, resulting in pattern loss, but according to the method of the present invention,
Since molten solder flows into and adheres to areas that are not solder plated, such accidents are eliminated.

〔Effect of the invention〕

As described above, according to the printed circuit board manufacturing method of the present invention, there is no pattern becoming thinner than the design dimension, pattern overhang phenomenon, or pattern missing, and a highly reliable printed circuit board can be obtained. There is.

[Brief explanation of the drawing]

1 to 2 are cross-sectional views showing the method for manufacturing a printed circuit board according to the present invention in the order of steps; FIGS. 3 to 9 are cross-sectional views showing the conventional method for manufacturing a printed circuit board in the order of steps; FIG. 10 is a sectional view showing an unfavorable state of a printed circuit board formed by a conventional method. In the figure, 1B is copper foil, 4 is a circuit pattern, 6 is a printed circuit board, and 8
9 is an electroless copper plating layer, 9 is an electrolytic copper plating layer, 10 is a resist pattern, 11 is a patterned copper plating layer, 12 is a solder plating layer, and 13 is a pattern forming layer. X 1 g 2nd figure fL Weihe Naki Kenyu 36+: box ti$mu tea 4th 2nd 5th meat suction wheel. y4 & transfer λnut+J%jj and 3゛λtoha・71shifp*energy i figure
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Claims (1)

[Claims] An electroless copper plating layer (8) and an electrolytic copper plating layer (9) are sequentially formed on a substrate (6) on which a copper foil (1B) is formed. ), a resist pattern (10) having a predetermined pattern is formed on the resist pattern (10).
) as a mask, after sequentially forming a patterned copper plating layer (11) and a solder plating layer (12) on the substrate (6), the resist pattern (10) is removed, and a pattern is formed below the resist pattern (10). The electrolytic copper plating layer (9
), a printed circuit board manufacturing method comprising a step of etching away an electroless copper plating layer (8) and a copper foil (1B) using the solder plating layer (12) as a mask, Electrolytic copper plating layer (9
), Electroless copper plating layer (8) A method for manufacturing a printed circuit board, characterized in that a step of melting the solder plating layer (12) is provided before the step of etching away the copper foil (1B).