JP7224940B2 - Method for manufacturing printed wiring board - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a method of manufacturing a printed wiring board having a conductive pattern plated with electrolytic noble metal.

Conventionally, after forming a circuit pattern consisting of each conductor pattern on a printed wiring board and then forming a solder resist pattern, electrolytic nickel plating and gold plating are applied to specific surfaces of the circuit pattern to which gold wires and solder are to be joined. It is
As described in Patent Literatures 1 and 2, after performing electrolytic plating, a part of the lead wire for electrolytic plating that is no longer needed is removed and cut.
In Patent Document 1, a plating resistant film (plating resist) covering the lead wire is peeled off during the electroplating process to expose the lead wire, and the lead wire is removed by etching.
In Patent Document 2, the solder resist covering the lead wires is removed with a laser during the electroplating process, the lead wires are exposed, and the lead wires are removed by etching.

JP-A-59-188997 Japanese Patent Application Laid-Open No. 2004-183043

However, even with the above-described prior art, there are the following problems.
Consider a case where lead wires for electroplating are covered with a plating resist as described in Patent Document 1. FIG.
For example, when the edge of the plating resist is placed on the conductor, the plating solution penetrates under the resist, and the lead wire for electrolytic plating is also plated, making it impossible to remove the lead wire for electrolytic plating by etching. Therefore, the edge of the planned portion of the plating facility cannot be formed with the plating resist. Therefore, the edge of the planned plating facility is formed with a solder resist.
Therefore, in addition to pattern formation of the solder resist, steps of pattern formation of the plating resist and removal of the plating resist are added.
If the plating resist and the solder resist do not overlap each other to a certain extent, the adhesion between the plating resist and the solder resist becomes insufficient, and the plating resist peels off, failing to fulfill its role as a resist.
Therefore, the edge of the plating resist cannot be placed on the conductor and must be placed on the solder resist, and the plating resist and the solder resist must overlap each other to a certain degree or more. A design that secures a margin for overlap is required, which may hinder high-density wiring design.

Consider a case where a solder resist covering a lead wire for electrolytic plating as described in Patent Document 2 is removed with a laser.
It is impossible to set a laser output that removes the solder resist and does not remove the insulating layer, which is a resin like the solder resist.
Therefore, when removing the solder resist with a laser as described in Patent Document 2, a shielding layer (dummy pattern in Patent Document 2) is required to prevent excessive removal of the insulating layer by the laser. If the shielding layer is not provided, the laser may reach the inner conductor layer directly below the outermost conductor layer, possibly causing disconnection.
Therefore, there is a process burden for patterning the shielding layer on the laser-processed portion. Also, the shielding layer increases the thickness of the printed wiring board. A conductor pattern that is not an actual circuit remains in the printed wiring board, which can be a hindrance to high-density wiring design.

A method for manufacturing a printed wiring board according to one aspect of the present disclosure is a method for manufacturing a printed wiring board having a circuit conductor in which a specific surface exposed from a solder resist is subjected to electrolytic noble metal plating,
Using the solder resist that covers lead wires for electroplating on the substrate connected to the circuit conductors on the substrate and exposes the specific surface as a mask, the circuit conductors are energized to a predetermined potential through the lead wires. and subjecting the specific surface to electrolytic precious metal plating,
Thereafter, a predetermined range of solder resist covering the lead wire is removed by cutting, and after the cutting, an etching resist is formed to cover the electrolytic precious metal plating and expose the predetermined range, and then the etching is performed. Etching is performed using the resist as a mask to remove the lead wire within the predetermined range, thereby cutting the lead wire from the circuit conductor.

According to the printed wiring board manufacturing method of the present disclosure, the solder resist is used as a mask during electroplating, and the solder resist is partially removed by cutting after the electroplating process, so the following effects are obtained.
Even if the edge of the mask for electroplating with solder resist is placed on the conductor, the plating solution does not penetrate under the mask.
In addition to solder resist pattern formation, the steps of plating resist pattern formation and plating resist removal become unnecessary, simplifying the process.
In addition, consideration of overlap with a plating resist provided separately from the solder resist becomes unnecessary, making it easy to achieve high-density wiring.
Since the removal of the solder resist on the lead wire for electroplating is performed by cutting, a shielding layer for stopping laser processing is not required, making it easy to achieve high-density wiring.

It is a sectional view explaining a manufacturing method of a printed wiring board of one embodiment. It is a sectional view explaining a manufacturing method of a printed wiring board of one embodiment. It is a sectional view explaining a manufacturing method of a printed wiring board of one embodiment. It is a sectional view explaining a manufacturing method of a printed wiring board of one embodiment. It is a sectional view explaining a manufacturing method of a printed wiring board of one embodiment. It is a sectional view explaining a manufacturing method of a printed wiring board of one embodiment. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example. It is sectional drawing explaining the manufacturing method of the printed wiring board of a comparative example.

A method for manufacturing a printed wiring board according to an embodiment of the present disclosure will be described with reference to the drawings.
As shown in FIG. 1, a solder resist 13 is formed to cover the circuit conductors 11 and lead wires 12 for electroplating formed on one main surface of the substrate 10 . However, the specific surface 11a of the circuit conductor 11, which is to be plated with noble metal, is exposed. A lead wire 12 for electrolytic plating is connected to the circuit conductor 11 . The substrate 10 is a multi-layer substrate having a circuit conductor layer inside if necessary.

As described above, the solder resist 13 covering the lead wires 12 for electroplating on the substrate 10 connected to the circuit conductors 11 on the substrate 10 and exposing the specific surface 11a is used as a mask, as shown in FIG. Electrolytic precious metal plating 14 is applied to the specific surface 11a. At this time, the circuit conductor 11 is energized to a predetermined potential via the lead wire 12 to deposit the electrolytic precious metal plating on the specific surface.
As the electrolytic noble metal plating 14, nickel plating and gold plating are formed in this order. A nickel plating is formed to a thickness of 2 μm or more, and then a gold plating is formed to a thickness of 0.2 μm or more.

Next, as shown in FIG. 3, a predetermined range 15 of the solder resist 13 covering the lead wires 12 is removed by cutting. Cutting is preferably performed with an NC drill or NC router. Excessive cutting of lower layers can be prevented by accurately controlling the cutting depth using numerical control (NC).
The predetermined range 15 includes the removed portion necessary for cutting the lead wire 12 and the periphery thereof as a margin.
By cutting, the solder resist 13 and the surface layer of the lead wires 12 thereunder are cut. Subsequently, the lead wire 12 is removed by proceeding with cutting until the interface between the lead wire 12 and the underlying insulating layer (substrate 10) is reached.
Thus, the lead wire 12 is cut off from the circuit conductor 11 by removing the lead wire 12 within the predetermined range 15 by the same cutting.
However, there are cases where the lead wires 12 cannot be completely removed by cutting alone due to the warp or unevenness of the substrate 10 .
Therefore, as shown in FIG. 3, when the lead wire 12 is left uncut, and before the lead wire 12 reaches the interface between the lead wire 12 and the underlying insulating layer (substrate 10), the cutting process is terminated to remove the lead wire 12. If left intentionally, the lead wire 12 within the predetermined range 15 is completely removed by etching described below after the main cutting step.

First, as shown in FIG. 4, an etching resist 16 covering the electrolytic precious metal plating 14 and exposing a predetermined area 15 is formed. A dry film is preferably used as the etching resist 16 .
Next, the lead wire 12 within a predetermined range 15 is removed by etching using the etching resist 16 as a mask (FIG. 5).
Next, the etching resist 16 is peeled off and removed (FIG. 6).

As described above, the printed wiring board 1 (FIG. 6) having the circuit conductors 11 with the electrolytic precious metal plating 14 applied to the specific surfaces 11a exposed from the solder resist 13 can be manufactured.

7 to 13 show steps of a comparative example. This is a method of exposing the lead wire by peeling off the plating resistant film (plating resist) covering the lead wire during the electrolytic plating process as described in Patent Document 1, and then removing the lead wire by etching.

In the comparative example, as shown in FIG. 7, the solder resist 13 is applied not only to the specific surface 11a of the circuit conductor 11 to be electroplated, but also to the lead wires 12 for electroplating (at least the portions required for cutting). ) are also exposed.
Next, as shown in FIG. 8, a plating resist 21 such as a dry film is formed to mask the lead wires 12 exposed from the solder resist 13 .
Next, as shown in FIG. 9, using the solder resist 13 and the plating resist 21 as a mask, electrolytic precious metal plating 14 is applied to the specific surface 11a.
Next, as shown in FIG. 10, the plating resist 21 is stripped and removed.
Next, as shown in FIG. 11, an etching resist 16 such as a dry film is formed to mask the electrolytic precious metal plating 14 .
Next, as shown in FIG. 12, the lead wires 12 are removed by etching using the solder resist 13 and the etching resist 16 as masks.
Next, as shown in FIG. 13, the etching resist 16 is stripped and removed.

According to the comparative example described above, in addition to the pattern formation of the solder resist 13, the steps of pattern formation of the plating resist 21 and removal of the plating resist 21 are required.
On the other hand, according to the present embodiment described above, in addition to the pattern formation of the solder resist 13, the steps of pattern formation of the plating resist and removal of the plating resist are not required, thereby simplifying the process.
According to the comparative example described above, it is necessary to overlap the solder resist 13 and the plating resist 21, and a design is required to secure a margin for the overlap, which may hinder high-density wiring design.
On the other hand, according to the present embodiment, there is no need to consider overlap with the plating resist provided separately from the solder resist, and high-density wiring can be easily realized.

Further, according to the present embodiment, even if the edge of the mask for electroplating with the solder resist 13 is placed on the conductor, the plating solution does not permeate under the solder resist 13 . Therefore, the electrolytic precious metal plating 14 can be accurately applied to the specific surface 11a.

In addition, comparison with the method of removing the solder resist covering lead wires for electrolytic plating as described in Patent Document 2 with a laser is as follows.
That is, according to this embodiment, since the removal of the solder resist 13 on the lead wire 12 for electroplating is performed by cutting, a shielding layer for stopping laser processing is not required. Even without the shielding layer, the lower layer wiring in the substrate 10 will not be disconnected.
Since the shielding layer becomes unnecessary, the wiring pattern included in the actual circuit can be arranged instead of the shielding layer, so that high-density wiring can be easily realized.

Although the embodiment of the present disclosure has been described above, this embodiment is shown as an example and can be implemented in various other forms. , can be replaced and changed.

Reference Signs List 1 printed wiring board 10 substrate 11 circuit conductor 11a specific surface 12 lead wire for electrolytic plating 13 solder resist 15 predetermined range 16 etching resist 21 plating resist

Claims (6)

A method for manufacturing a printed wiring board having circuit conductors electrolytically plated with noble metal on a specific surface exposed from a solder resist,
Covering lead wires for electrolytic plating on the substrate connected to the circuit conductors on the substrate and exposing the specific surface of the solder resist is used as a mask to set the circuit conductors to a predetermined potential through the lead wires. Energizing to apply electrolytic precious metal plating to the specific surface,
Thereafter, a predetermined range of solder resist covering the lead wire is removed by cutting, and after the cutting, an etching resist is formed to cover the electrolytic precious metal plating and expose the predetermined range, and then the etching is performed. A method of manufacturing a printed wiring board , wherein etching is performed using a resist as a mask to remove the lead wire within the predetermined range, thereby cutting the lead wire from the circuit conductor. 2. The method of manufacturing a printed wiring board according to claim 1 , wherein said electrolytic precious metal plating is formed in order of nickel plating and gold plating. 3. The method of manufacturing a printed wiring board according to claim 2 , wherein the nickel plating is formed to a film thickness of 2 [mu]m or more. 4. The method of manufacturing a printed wiring board according to claim 2 , wherein the gold plating is formed to have a film thickness of 0.2 [mu]m or more. 5. The method of manufacturing a printed wiring board according to claim 1 , wherein said cutting is performed by an NC drill. 5. The method of manufacturing a printed wiring board according to claim 1 , wherein said cutting is performed by an NC router.

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