JP2009253118A - Method for manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a conventional method for manufacturing a wiring board wherein the width of a recession, where the outer peripheral surface of a terminal pad is exposed, becomes uneven when the recession is formed by light exposure and development. <P>SOLUTION: The whole exposed surface of the base 12 of a terminal pad formed on one surface of a wiring board 10 is coated with a nickel layer 18 of a given thickness. The whole of the base 12 including the nickel layer 18 is then covered with a permanent resist layer 20. Subsequently, the permanent resist layer 20 is polished to expose the upper face of the nickel layer 18. The nickel layer 18 is then removed by etching to form a recession 22 along the outer peripheral edge of the base 12, where the outer peripheral surface of the base 12 is exposed to an inner wall surface in the recession 22. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a wiring board, and more particularly to a method for manufacturing a wiring board in which terminal pads are formed on one side.

As terminal pads formed on one surface side of a wiring board used for a semiconductor device or the like, there are those shown in FIGS. 8A and 8B.
In the terminal pad shown in FIG. 8A, the vicinity of the periphery of the terminal pad 102 formed on one surface side of the wiring substrate 100 is covered with a resin layer 104 that covers the one surface side of the wiring substrate 100. The terminal pad shown in FIG. 8A is called an SMD structure (Solder Mask Defined structure).
On the other hand, in the terminal pad shown in FIG. 8B, a concave groove 206 is formed between the terminal pad 202 formed on one surface side of the wiring board 200 and the resin layer 204, and the terminal pad 202 is concave. It is surrounded by the groove 206. The terminal pad shown in FIG. 8B is called an NSMD structure (Non-Solder Mask Defined structure).
The SMD structure of the terminal pad 102 is covered with the resin layer 104 in the vicinity of the periphery thereof, so that it is necessary to secure an exposed area necessary for the terminal formed on the exposed surface of the terminal pad 102. The size of the terminal pad 102 is increased only in the portion covered with 104.
Furthermore, in order to ensure that the resin layer 104 is coated in the vicinity of the periphery of the terminal pad 102, the width of the portion of the terminal pad 102 covered by the resin layer 104 is secured in consideration of processing accuracy. The terminal pad 102 is further enlarged.
On the other hand, the terminal pad 202 having the NSMD structure can be made smaller than the terminal pad 102 having the SMD structure because the entire terminal pad 202 is exposed. For this reason, the terminal pad 202 having the NSMD structure is effective for reducing the size of the wiring substrate 200 and making the wiring pattern finer.

A method of manufacturing a wiring board having such a terminal pad 202 having an NSMD structure is described in, for example, Patent Document 1 below.
FIG. 9 shows a method of manufacturing a wiring board provided with the NSMD structure terminal pad 202. In the method of manufacturing the wiring board shown in FIG. 9, as shown in FIG. 9A, after the base 202a and the wiring pattern 208 of the terminal pad 202 are formed on one surface side of the wiring board 200 with copper or the like, the base 202a and The exposed surface of the wiring pattern 208 is covered with the nickel layer 210 [FIG. 9B].
Next, as shown in FIG. 9C, after the base 202a covered with the nickel layer 210 and the entire wiring pattern 208 are covered with a resin layer 204 such as a solder resist, the resin layer 204 is patterned by exposure and development. Then, a concave groove 206 is formed in which the outer peripheral surface of the base portion 202a covered with the nickel layer 210 is exposed on the inner wall surface [FIG. 9 (d)].
Thereafter, as shown in FIG. 9E, a protective film 216 is formed on the exposed surface of the nickel layer 210 of the base portion 202a by gold plating or the like to form the terminal pad 202, and then the protective film of the terminal pad 202 is formed. The external connection terminals 214 can be formed by mounting solder balls on 216 and performing reflow.
JP 2007-67147 A

In the method for manufacturing a wiring board shown in FIG. 9, a terminal pad 202 having an NSMD structure can be formed on one side of the wiring board.
However, in the method for manufacturing the wiring board shown in FIG. 9, the resin groove 204 covering the entire base portion 202a and the wiring pattern 208 is subjected to patterning by exposure and development to form the concave groove 206.
In the step of forming the concave groove 206 by such exposure / development, the processing accuracy in each step of exposure, development and removal of the resin layer 204 is laminated, and the accuracy of the concave groove 206 to be finally formed is lowered. In particular, when the wiring pattern 208 or the like is refined, the terminal pads 202 and the recessed grooves 206 are also refined.
However, when the concave groove 206 refined by exposure / development is formed, the width of the concave groove 206 becomes nonuniform as shown in FIG. Therefore, when a solder ball is mounted on the terminal pad 202 shown in FIG. 10 and reflowed to form the external connection terminal 214, a part of the external connection terminal 214 comes into contact with the resin layer 204 as shown in FIG. Sometimes.

As described above, in a state where a part of the external connection terminal 214 is in contact with the resin layer 204, stress is applied to the part of the external connection terminal 214 in contact with the resin layer 204 when a heat shock is applied to the wiring board 200. May cause cracks in the external connection terminals 214 and the external connection terminals 214 may fall off.
For this reason, the groove 206 formed by exposure / development needs to secure a width in consideration of the processing accuracy, and the terminal pad 202 having the NSMD structure has a limit in miniaturization.
Therefore, the present invention solves the problem of the conventional method of manufacturing a wiring board in which the width of the groove is non-uniform when the groove that exposes the outer peripheral surface of the terminal pad is formed by exposure and development. It is an object of the present invention to provide a method for manufacturing a wiring board capable of forming a concave groove that is as uniform as possible and whose outer peripheral surface of a terminal pad is exposed on an inner wall surface.

As a result of studying to solve the above problems, the present inventors polished a resin layer covering a plating metal layer having a predetermined thickness covering the entire exposed surface of the base portion of the terminal pad formed on one side of the wiring board, After the upper surface of the plated metal layer was exposed, it was found that a groove having a uniform width could be formed on the outer peripheral surface of the base by removing the plated metal layer by etching, and the present invention was achieved.
That is, according to the present invention, the entire exposed surface of the base portion of the terminal pad formed on at least one surface side of the wiring board is covered with the plating metal layer having a predetermined thickness, and then the entire base portion including the plating metal layer is covered with the resin layer. Then, after removing the resin layer so that at least the upper surface of the plated metal layer is exposed, the plated metal layer is removed by etching, and is formed along the outer periphery of the base. A method of manufacturing a wiring board is characterized in that a concave groove having an outer peripheral surface exposed to an inner wall surface is formed.
In the present invention, when the terminal pad is formed by removing the resin layer by polishing and projecting the upper surface of the plated metal layer from the polished surface, the upper surface of the terminal pad and the upper surface of the resin layer are flush with each other. Can be.
Alternatively, the upper surface of the base portion of the terminal pad can be made higher than the polished surface of the resin layer by removing the resin layer by blast polishing. For this reason, a low melting point metal such as a solder ball can be easily attached to the upper end of the base of the terminal pad.
Further, by forming the plated metal layer by electroless plating, the plated metal layer can be formed on the base that is difficult to feed.
In particular, it is preferable to form a columnar base portion made of copper as the base portion of the terminal pad and to form a nickel plating layer on the exposed surface of the base portion by electroless nickel plating.
Further, it is preferable to form a groove having a width of 2 to 20 μm as the groove, and to form a terminal pad by covering the exposed surface of the base with a protective film thinner than the plated metal layer.
By mounting a solder ball on the terminal pad and performing reflow, a terminal portion made of solder can be easily formed.
As the base portion of the terminal pad, a columnar base portion made of copper may be formed, or a columnar base portion formed by covering the resin portion with a metal layer may be formed.

In the present invention, the entire exposed surface of the base portion of the terminal pad formed on at least one surface side of the wiring board is covered with a solder layer having a predetermined thickness formed by plating, and then the entire base portion including the solder layer is covered. The resin layer is then covered, and then the resin layer is removed so that the upper surface of the solder layer is exposed. Then, the solder layer is subjected to reflow, and the solder layer is surrounded by the concave groove formed. It is also a method for manufacturing a wiring board, characterized in that a terminal portion made of solder is formed at the distal end portion of the base portion.
In the present invention, by forming the solder layer by electroless solder plating, the solder layer can be formed on the base that is difficult to feed.

According to the method of manufacturing a wiring board according to the present invention, the resin layer covering the base of the terminal pad whose exposed surface is coated with the plated metal layer is polished to expose the upper surface even if the plated metal layer is small. After that, the plating metal is removed by etching to form a recess.
The thickness variation of the plated metal layer can be made smaller than the processing accuracy of exposing / developing the resin layer, and the groove formed by removing the plated metal layer is formed by exposing / developing the resin layer. The variation in the width can be made as small as possible than the concave groove.
As a result, the concave groove formed along the outer peripheral edge of the base portion of the terminal pad and having the outer peripheral surface of the base portion exposed to the inner wall surface can be formed as uniformly as possible. For this reason, the terminal part formed in the terminal pad finally obtained can prevent cracks and the like due to uneven distribution of stress generated by partial contact with the resin layer. Further, the pad pitch between the terminal pads can be reduced.

An example of a method for manufacturing a wiring board according to the present invention is shown in FIGS. First, as shown in FIG. 1A, terminal pad bases 12, 12... And wiring patterns 14, 14... Made of copper are formed on one surface side of a resin wiring board 10. The base portions 12, 12,... And the wiring patterns 14, 14,... Have the same height and are columnar. .. And the wiring patterns 14, 14... Can be formed by a known additive method, semi-additive method, or subtractive method.
After the formed base portions 12, 12,... And wiring patterns 14, 14,... Are covered with a plating resist layer, the plating resist layer is exposed and developed, and as shown in FIG. The base portions 12, 12,... Are exposed in a state in which 14, 14,.
The exposed bases 12, 12,... Are covered with a nickel layer 18 as a plating metal layer by electroless nickel plating, as shown in FIG. The thickness of the nickel layer 18 is preferably 2 to 20 μm.
As shown in FIG. 1 (c), in order to form the nickel layer 18 only on the bases 12, 12,... By electroless nickel plating, the exposed surfaces of the bases 12, 12,. Then, after soft etching and acid cleaning, Pd activation treatment is performed. At this time, Pd nucleation is selectively performed only on the exposed surfaces of the bases 12, 12,. Next, the wiring board 10 is immersed in a predetermined electroless nickel plating solution, and the immersion time is adjusted, whereby the nickel layer 18 having a uniform thickness and a predetermined thickness is formed only on the exposed surfaces of the bases 12, 12,. Can be formed.
Next, the plating resist layer 16 covering the wiring patterns 14, 14,... Is removed, and the base portions 12, 12, .. and the wiring patterns 14, 14,. Covered with a permanent resist layer 20.

As shown in FIG. 2A, the permanent resist layer 20 is subjected to polishing by blast polishing in which particles are sprayed onto the polishing surface at portions corresponding to the upper surfaces of the base portions 12, 12,. .. The upper surface of the nickel layer 18 covering the.
This blast polishing is not performed on the permanent resist layer 20 covering the wiring patterns 14, 14,... Because the thickness of the permanent resist layer 20 covering the upper surfaces of the wiring patterns 14, 14,.
In this way, by removing the nickel layer 18 whose upper surface is exposed by etching as shown in FIG. 2 (b), concave grooves 22 are formed along the outer peripheral edges of the bases 12, 12,. The The outer peripheral surface of the base 12 is exposed on each inner wall surface of the concave grooves 22, 22.
Since the concave grooves 22, 22... Are formed by removing the nickel layer 18 by etching, the width is equal to the thickness of the nickel layer 18 and is preferably 2 to 20 μm.

In this way, since the concave grooves 22, 22... Are formed by etching away the nickel layer 18 formed by electroless nickel plating, the variation in the width is equal to the variation in the thickness of the nickel layer 18. . For this reason, the variation in the width of the concave grooves 22, 22,... Can be made extremely small compared to the variation in the width of the concave grooves formed in the resin layer by exposure and development.
Further, on the outer peripheral surface of the base 12, 12,... Exposed on the inner wall surface of the concave groove 22 formed along the outer peripheral edge, as shown in FIG. To form a terminal pad 25. As the protective coating 24, a thin gold layer or palladium layer is formed by electroless plating on the thin nickel layer covering the exposed surface of the base 12.
Thereafter, solder balls are mounted on the upper surfaces of the terminal pads 25, 25,... And reflowed to form terminal portions.
As the protective film 24, an organic thin film such as an aqueous preflux may be formed.

As shown in FIG. 3, each of the terminal pads 25, 25... Has a step h formed between the permanent resist layer 20 and the upper surface of the terminal pad 25, but the terminal pads 25, 25. Each is surrounded by a concave groove 22 having a width as uniform as possible.
For this reason, when the permanent resist layer 20 formed between the terminal pads 25 and 25 is mounted with solder balls and reflowed to form the terminal portion, the molten solder flows out to the adjacent terminal pads. It also serves as a barrier that can be prevented.
Moreover, the terminal portions formed in each of the terminal pads 25, 25,... Can prevent cracks and the like due to uneven distribution of stress generated by partial contact with the permanent resist layer 20.

As shown in FIG. 3, in order to form the permanent resist layer 20 and the terminal pad 25 flush with each other without forming a step h between the permanent resist layer 20 and the terminal pad 25, FIG. It is preferable to employ the manufacturing method shown.
In the manufacturing method shown in FIG. 4, in the same manner as in the steps shown in FIGS. 1A to 1D, the base portions 12, 12,... And the wiring patterns 14, 14,. When the nickel resist layer 18 is exposed by blasting the permanent resist layer 20 after being covered with the layer 20, as shown in FIG. 4A, the upper surface of the nickel layer 18 protrudes from the polished surface. The permanent resist layer 20 is blast polished.
The reason why the upper surface of the nickel layer 18 can protrude from the polished surface by blast polishing is that the nickel layer 18 that is a metal is harder than the permanent resist layer 20.
Next, as shown in FIG. 4B, by removing the nickel layer 18 by etching, bases 12, 12,... Whose upper surface is slightly lower than the polished surface can be obtained.
When the exposed surfaces of the bases 12, 12,... Are covered with a protective film 24 to form terminal pads 25 as shown in FIG. 4C, the permanent resist layer 20 and the terminals are formed as shown in FIG. The upper surface of the pad 25 can be flush with the upper surface.
In this manner, even if the permanent resist layer 20 and the terminal pad 25 are formed flush with each other, the terminal pad 25 is surrounded by the concave groove 22, so that even if the solder ball is mounted and reflowed, it is adjacent. It is possible to prevent the molten solder from flowing out to the terminal pad 25 to be performed.

In the wiring board 10 shown in FIGS. 1 to 5, the wiring pattern 14 formed on the one surface side of the wiring board 10 and the base 12 have the same height. However, as shown in FIG. It may be lower than the base 12.
In this case, when the base portions 12, 12,... And the wiring patterns 14, 14,... Are covered with the permanent resist layer 20, the permanent resist covering the wiring patterns 14, 14,. The thickness of the layer 20 can be sufficiently maintained.
For this reason, when the upper surface of the nickel layer 18 covering the base portions 12, 12... Is exposed by polishing the permanent resist layer 20, the entire surface of the permanent resist layer 20 is uniformly formed as shown in FIG. You may grind | polish.
Next, as shown in FIG. 2B, the nickel layer 18 covering the base 12 is removed by etching to form the concave groove 22, and then the base 12 is formed on the nickel layer 18 as shown in FIG. The terminal pad 25 is formed by covering with a thinner protective coating 24.

1 to 6, the nickel layer 18 having a predetermined thickness is formed on the exposed surfaces of the base portions 12, 12..., But as shown in FIG. A solder layer 26 having a predetermined thickness may be formed on the exposed surfaces of the bases 12, 12,. The solder layer 26 may be formed by electrolytic plating, but can also be formed by electroless plating on the base 12 where power cannot be supplied.
In order to form the solder layer 26 only on the exposed surface of the base 12, 12,... By such electroless plating, the exposed surface of the base 12, 12,. The process is applied. At this time, Pd nucleation is selectively performed only on the exposed surfaces of the bases 12, 12,. Next, the wiring substrate 10 is immersed in a predetermined electroless solder plating solution, and the immersion time is adjusted, so that a solder layer 26 having a uniform thickness and a predetermined thickness is formed only on the exposed surfaces of the bases 12, 12,. Can be formed. The thickness of the solder layer 26 is preferably 2 to 20 μm.

The base portions 12, 12... Covered with the solder layer 26 having a predetermined thickness are covered with the permanent resist layer 20 together with the wiring patterns 14, 14... Formed on the same surface of the wiring substrate 10. As shown in a), the upper surfaces of the solder layers 26, 26,... are exposed by blast polishing.
After that, the wiring board 10 is placed in a heated atmosphere, and the solder layers 26, 26,... Are reflowed, so that the molten solder is subjected to surface tension as shown in FIG. The terminal portions 28 can be formed by gathering on the respective upper surfaces.
The portions where the solder layers 26, 26,... Are formed are formed in the concave grooves 22, 22,... Where the peripheral surfaces of the base portions 12, 12,.
Instead of the base 12 shown in FIG. 7, the terminal pad 25 may be used by forming a protective film 24 on the exposed surface of the base 12.

1 to 7, the wiring patterns 14, 14... Are not covered with the nickel layer 18, but are covered with the nickel layer 18 and covered with the permanent resist layer 20 like the base portions 12, 12. It may be.
1 to 7, the base portions 12, 12... Are made of copper. However, the base portion 12, 12 is formed by covering a resin portion made of the same resin as or different from the resin forming the wiring substrate 10 with a metal layer. 12... May be formed.
Further, in the wiring substrate 10 shown in FIGS. 1 to 7, the base portions 12, 12,... Are formed on one surface side, but the base portions 12, 12,. Then, terminal pads may be formed on both sides of the wiring board 10.

It is a part of process drawing for demonstrating an example of the manufacturing method of the wiring board which concerns on this invention. It is the remainder of the process drawing for demonstrating an example of the manufacturing method of the wiring board which concerns on this invention. FIG. 3 is a partial enlarged cross-sectional view of a wiring board obtained by the method for manufacturing a wiring board shown in FIGS. 1 and 2. It is process drawing for demonstrating the other example of the manufacturing method of the wiring board which concerns on this invention. It is the elements on larger scale of the wiring board obtained with the manufacturing method of the wiring board shown in FIG. It is process drawing for demonstrating the other example of the manufacturing method of the wiring board which concerns on this invention. It is process drawing for demonstrating the other example of the manufacturing method of the wiring board which concerns on this invention. It is explanatory drawing explaining the kind of terminal pad formed in a wiring board. It is process drawing explaining the manufacturing method of the conventional wiring board. It is sectional drawing of the wiring board obtained with the manufacturing method of the conventional wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wiring board 12 Base 14 Wiring pattern 16 Resist layer 18 for plating Nickel layer (metal layer for plating)
20 Permanent resist layer (resin layer)
22 Concave groove 24 Protective film 25 Terminal pad 26 Solder layer 28 Terminal portion

Claims (13)

After covering the entire exposed surface of the base portion of the terminal pad formed on at least one side of the wiring board with a plating metal layer having a predetermined thickness, the entire base portion including the plating metal layer is covered with a resin layer,
Next, after removing the resin layer so that at least the upper surface of the plated metal layer is exposed, the plated metal layer is removed by etching, and the outer peripheral surface of the base is formed along the outer peripheral edge of the base. A method of manufacturing a wiring board, comprising forming a recessed groove exposed on an inner wall surface.   When the resin layer is removed by polishing to form a terminal pad, the upper surface of the plated metal layer protrudes from the polished surface so that the upper surface of the base of the terminal pad and the upper surface of the resin layer are flush with each other. The manufacturing method of the wiring board of Claim 1.   2. The method for manufacturing a wiring board according to claim 1, wherein the resin layer is removed by blast polishing, and the upper surface of the base portion of the terminal pad is made higher than the polished surface of the resin layer.   The manufacturing method of the wiring board as described in any one of Claims 1-3 which forms a plating metal layer by electroless plating.   The wiring board manufacturing method according to any one of claims 1 to 4, wherein a columnar base portion made of copper is formed as a base portion of a terminal pad, and a nickel plating layer is formed on the exposed surface of the base portion by electroless nickel plating. Method.   The method for manufacturing a wiring board according to claim 1, wherein a concave groove having a width of 2 to 20 μm is formed as the concave groove.   The manufacturing method of the wiring board as described in any one of Claims 1-6 which coat | covers the exposed surface of the base part of a terminal pad with a protective film thinner than a metal plating layer, and forms a terminal pad.   The method for manufacturing a wiring board according to claim 1, wherein a solder ball mounted on the terminal pad is reflowed to form a terminal portion made of solder. After covering the entire exposed surface of the base of the terminal pad formed on at least one side of the wiring board with a solder layer having a predetermined thickness formed by plating, the entire base including the solder layer is covered with a resin layer,
Next, after removing the resin layer so that the upper surface of the solder layer is exposed, the solder layer is subjected to reflow, and the tip of the base portion surrounded by the concave groove where the solder layer was formed is applied. A method of manufacturing a wiring board, comprising forming a terminal portion made of solder.   The method for manufacturing a wiring board according to claim 9, wherein the solder layer is formed by electroless solder plating.   11. The method for manufacturing a wiring board according to claim 9, wherein a columnar base portion made of copper is formed as a base portion of the terminal pad.   The method for manufacturing a wiring board according to claim 9 or 10, wherein a columnar base portion formed by covering a resin portion with a metal layer is formed as a base portion of a terminal pad.   The method for manufacturing a wiring board according to claim 1, wherein the base portion of the terminal pad is the base portion of the external connection terminal pad.

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