JP4694349B2 - Printed wiring board using laser processing and manufacturing method thereof - Google Patents

Description

  The present invention relates to a method for manufacturing a printed wiring board by laser via processing.

  In recent years, with the reduction in size and weight of electronic devices, there has been a demand for higher density of printed wiring boards, and the number of printed wiring boards is increasing. In order to increase the number of layers, it is necessary to ensure electrical continuity between wiring layers in which a circuit is formed via an insulating layer. Interlayer connection is an important factor in multilayer printed wiring board manufacturing technology.

As an interlayer connection method of the wiring layer, there are a through hole which is a through hole, a blind via hole which is a non-through hole, an interstitial via hole and the like. This hole forming method includes a drilling method, a laser processing method, and the like, but the laser processing method is mainly used from the viewpoint of reducing the diameter of the processing hole and increasing the processing speed. Among them, the CO ₂ laser having high laser energy is most popular. In the wavelength region of the CO ₂ laser, processing is difficult because the laser light is reflected on the surface of the copper foil. Therefore, a large window method has been employed in which only the copper foil around the hole forming periphery is removed by etching in advance.

  However, the large window method requires a copper foil patterning process and requires a copper foil etching diameter that is approximately twice the laser diameter to correct the laser beam hole misalignment. It is difficult to refine the design. Therefore, a direct via processing technique in which a copper foil and an insulating layer are simultaneously processed with a direct laser is being studied. The direct via processing method is a method that increases the absorption rate of laser light by roughening the surface of the copper foil and enables processing of the copper foil. Examples of the roughening treatment on the surface of the copper foil include a blackening treatment for forming a copper oxide film of needle-like crystals and a treatment for directly roughening copper by copper grain boundary etching.

JP 2002-217551 A

  When direct via processing is performed using a laser on a copper clad laminate with a roughened copper foil surface, Cu melted by the heat of the laser scatters and adheres in a convex shape around the via opening. Occurrence of melt scattering Cu and so-called overhang in which the hole diameter of the outer layer copper foil is smaller than the hole diameter of the insulating layer occur. Fig. 1 is a schematic diagram showing melt-sputtered Cu and overhang generated by performing direct via processing on a copper-clad laminate, Fig. 1 (a) is a top view, and Fig. 1 (b) is its AA cross-sectional view. is there. When an outer layer copper foil 3 is formed on an insulating layer 1 having an inner layer wiring 2 and a copper clad laminate having a copper oxide film 4 formed on the surface thereof is irradiated with laser light and via processing is performed, a peripheral portion of the opening is formed. Melt scattering Cu and overhang 5 occur. The molten scattering Cu and the overhang 5 need to be removed in the subsequent process in order to reduce the via throwing power of the via and the flatness during lamination. Removal methods include physical polishing such as buffing and chemical etching with a chemical solution. However, there is a problem that the outer layer copper foil or the inner layer wiring is polished or etched by the removal process of the molten scattered Cu and the overhang, and the wiring thickness is reduced.

  An object of the present invention is to provide a direct via processing process capable of removing the melt-scattered Cu and overhang without reducing the wiring thickness.

The present invention relates to a method of manufacturing a printed wiring board in which a blind via process is directly performed on a copper foil using a laser on a copper clad laminate in which a copper foil is bonded to a base resin. It is characterized by selectively removing molten and scattered Cu and overhangs generated in the vicinity. Specifically, the blind via processing step is the step of forming an oxide film on the surface of the copper foil, the laser via processing step, the insulating layer residue on the bottom of the via at the time of the laser via processing, and the insulating layer generated on the via wall surface. An alkali treatment step for removing deposits , a melt-scattering Cu etching treatment step, and a desmear treatment step for removing resin residue on the via bottom are performed in this order. In the alkali treatment step, the treatment is preferably performed with a treatment solution containing sodium hydroxide or potassium hydroxide. The pH is preferably 12 or more. In the molten splash Cu etching process, a treatment solution containing ammonium persulfate, a treatment solution containing sodium persulfate, a treatment solution containing ferric chloride, a treatment solution containing ammonia and hydrogen peroxide, or a treatment containing ammonia and copper chloride. It is preferable to perform the treatment with a liquid.

  According to the printed wiring board manufacturing method of the present invention, the decrease in the inner layer wiring thickness before and after the formation of the laser via can be suppressed to 0.5 μm or less. Further, the decrease in the thickness of the outer layer copper foil before and after the formation of the laser via can be suppressed to 1.0 μm or less.

  The printed wiring board manufactured by the manufacturing method of the present invention typically has an outer layer copper foil etching width of 20 μm or less at the end of the via, and a positional deviation rate between the outer layer circuit and the via of 5% or less. The reduction amount of the inner layer wiring thickness in the portion is 0.5 μm or less.

  By applying the direct via processing process of the present invention, it is possible to selectively remove molten and scattered Cu and overhangs generated during laser processing, and the via shape and wiring dimension accuracy of the printed wiring board are improved.

Embodiments of the present invention will be described below with reference to the drawings.
In the printed wiring board manufacturing method of the present invention, as shown in FIG. 2, the direct via processing process includes: (a) copper foil surface oxide film formation, (b) laser via processing, (c) alkali treatment, (d) melt scattering Cu etching treatment and (e) desmear treatment are desirable. In order to selectively remove molten and scattered Cu and overhangs, in the direct via processing process, a copper oxide film is formed on the surface of the copper foil until the molten and scattered Cu and overhang are removed. It is important to leave Further, in order to completely remove the molten scattered Cu, the deposits derived from the insulating layer must be removed by alkali treatment before the treatment.

  Copper foil surface oxide film formation is a process of forming a copper oxide film having a thickness of 0.5 μm or more on the surface of the outer layer copper foil. When this copper oxide film thickness is 0.5 μm or less, the etching resistance is lowered, and the selectivity between the molten scattered Cu and the copper oxide film is lowered. In the present invention, as a method for forming a copper oxide film, a blackening treatment that can simultaneously obtain roughening of the copper foil surface and formation of copper oxide is used. The blackening treatment liquid in the present invention is not particularly limited, and a commercially available treatment liquid is used.

The laser used for laser via processing is not particularly limited in the wavelength range of ultraviolet rays and infrared rays, but in the examples described below, a CO ₂ laser having a laser beam wavelength of 9.3 to 10.6 μm was used.

  The alkali treatment is a treatment for removing deposits derived from the insulating layer generated during laser processing. During laser processing, deposits derived from the insulating layer adhere to the surface of the molten scattering Cu and the overhang portion, and during etching, the molten scattering Cu and the overhang portion are protected and cannot be completely removed. Therefore, it is necessary to perform this alkali treatment before the etching treatment to remove the deposits derived from the insulating layer adhering to the surface of the molten scattered Cu and the overhang portion. Further, in this alkali treatment, the insulating layer residue on the bottom of the via is not removed, and only the deposit derived from the insulating layer generated on the via wall surface can be selectively removed. The alkaline treatment liquid in the present invention is an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide having a pH of 12 or higher.

  The melt-sputtered Cu etching process is a process for selectively removing the melt-scattered Cu and overhangs, and it is desirable that the treatment liquid has a low solubility of the copper oxide film and a high solubility of the melt-scattered Cu. The melt-sputtering Cu etching solution in the present invention is a ferric chloride solution, a persulfate-based or ammonia-based Cu etching solution.

  The desmear process is a process for removing a resin residue at the bottom of the via that cannot be completely removed during laser processing. The treatment process is performed by swelling treatment, oxidation treatment, and neutralization treatment. The desmear treatment liquid in the present invention is not particularly limited, and a commercially available treatment liquid is used.

  The printed wiring board of the present invention is not particularly limited, and is a generally known rigid or flexible circuit board having copper foil on both sides or one side of resin including resin or glass cloth.

  FIG. 3 is a schematic diagram showing a printed wiring board manufacturing process according to the present invention, FIG. 3 (a) to FIG. 3 (d) show an inner layer circuit formation process, and FIG. 3 (e) to FIG. 3 (h) are outer layers. The circuit formation process is shown.

  FIG. 3A is a schematic view of the inner layer base material 7. In this example, Hitachi Chemical Co., Ltd. copper-clad laminate MCL-E679 was used as the inner layer base material, and after forming the inner layer circuit resist pattern on the copper foil as shown in FIG. As shown in FIG. 5B, Cu was removed by etching using the resist as a mask to form the inner layer circuit 2. Next, as shown in FIG. 3 (d), a single-sided copper foil-attached polyimide sheet was laminated on the inner layer base material 7 on which the inner layer circuit 2 was formed by pressing to prepare a four-layer copper-clad laminate. The thickness of the polyimide layer (insulating layer) 1 was 30 μm, and the thickness of the outer layer copper foil 3 was 6 μm. Next, direct via processing was performed as shown in FIG.

The direct via machining process shown in FIG. 3 (e) will be described with reference to FIG.
1. Copper foil surface oxidation treatment (Figure 2 (a))
First, a blackening treatment was performed to roughen the surface of the outer layer copper foil 3 of the copper-clad laminate and form the copper oxide film 4. As the blackening solution, Propond 80 manufactured by ROHM and HAAS was used. The treatment conditions were a liquid temperature of 80 ° C. and a treatment time of 5 minutes. The formed copper oxide film thickness is 0.8 μm.

2. Laser via processing (Figure 2 (b))
Next, blind via processing was performed on the copper-clad laminate that had been blackened with a CO ₂ laser. The laser energy was 10 mJ and the via diameter was 100 μm. At this time, molten scattering Cu and overhangs 5 were formed around the via opening, and deposits 6 derived from the insulating layer were generated on the via wall surfaces.

3. Alkali treatment (Figure 2 (c))
Next, an alkali treatment was performed to remove the deposit 6 derived from the insulating layer generated on the via wall surface during laser processing. The alkali treatment liquid had a sodium hydroxide concentration of 50 g / l, and the treatment conditions were a liquid temperature of 50 ° C. and a treatment time of 3 minutes.

4). Melt-sputtered Cu etching process (Figure 2 (d))
Next, an etching process was performed in order to remove the molten scattered Cu and the overhang 5. The etching solution was 200 g / l ammonium persulfate and 5 ml / l sulfuric acid, and the treatment conditions were a solution temperature of 30 ° C. and a treatment time of 3 minutes. About processing time, it is time required in order to remove molten scattering Cu and the overhang 5 completely.

5. Desmear treatment (Figure 2 (e))
Next, desmear treatment was performed to remove the resin residue at the bottom of the via. In the desmear treatment, the swelling solution used was Circum Holeprep 4125 manufactured by ROHM and HAAS, and the solution temperature was 70 ° C. and the treatment time was 5 minutes. As the oxidizing solution, Circuit MLB Promoter213 manufactured by ROHM and HAAS was used, and the solution temperature was 80 ° C. and the treatment time was 5 minutes. As the neutralization solution, Circuit MLB Neutralizer 216-5 manufactured by ROHM and HAAS was used, and the solution temperature was 40 ° C. and the treatment time was 5 minutes.

  After the direct via process, an outer layer circuit was formed as shown in FIGS. 3 (f) to 3 (h). First, as shown in FIG. 3 (f), a copper plating film 9 was formed to have a thickness of 15 μm in order to form an interlayer conduction of the processed blind via. Next, as shown in FIG. 3 (g), the outer layer circuit resist pattern 8 is formed on the copper plating film 9, and the outer layer is etched with ferric chloride solution as shown in FIG. Circuit 10 was formed to produce a multilayer printed wiring board.

  A cross-sectional observation was performed in order to investigate the removal state of the melt-scattered Cu and overhangs in the multilayer printed wiring board produced above and the reduction width of the outer layer copper foil and the inner layer wiring by the etching process. The samples were processed after laser via processing in the direct via processing process and after desmear processing. The results are shown in FIG.

  As a result of the removal of molten splash Cu and overhang, after laser via processing, molten splash Cu and overhang occurred on the outer copper foil around the via, but after desmear treatment, the area where molten splash Cu occurred around the via All of the outer layer copper foil was removed. The external appearance was the same as the shape obtained by etching the outer layer copper foil before laser processing by the large window method, and the outer layer copper foil was all etched slightly larger than the processed via diameter. Therefore, as shown in FIG. 5, the distance from the end of the via to the end of the outer layer copper foil was measured as the outer layer copper foil etching width X. The result was 13 μm. The smaller the outer layer copper foil etching width, the smaller the land diameter of the outer layer circuit.

  The thickness of the outer layer copper foil was reduced by 0.5 μm after desmearing compared to the thickness after laser via processing. Regarding the inner layer wiring thickness, the thickness after desmearing was reduced by 0.5 μm compared to the thickness after laser via processing.

  As described above, by using the direct via processing process of the present invention, it is possible to remove the molten scattered Cu and the overhang without substantially reducing the thicknesses of the inner layer wiring and the outer layer copper foil.

  Furthermore, after forming a multilayer printed wiring board having four layers, the positional deviation between the outer layer circuit and the via was evaluated. As shown in FIG. 6, the via misalignment evaluation method measures the distance S from the center a of the via to the center b of the outer layer circuit 10, and sets the via diameter as Vr, and the via misalignment rate = S / Vr × 100%. Evaluation was performed. As a result, the maximum value of the measured via position deviation rate is shown in FIG. As a result, in order to process the outer layer copper foil and the via simultaneously, the positional deviation rate between the outer layer circuit and the via was 5% or less. Further, the land diameter Lr of the outer layer circuit is 210 μm with respect to the via diameter of 100 μm.

  (C) Sodium hydroxide concentration of alkali treatment solution in the direct via processing process was changed in the range of 10-100 g / l, printed wiring board was produced in the same way as in Example 1, and the molten scattered Cu and overhang were removed The outer layer copper foil etching width was measured, and the thickness of the outer layer copper foil and inner layer wiring was evaluated for the reduction width. The results are shown in FIG. Moreover, each alkali processing condition is shown in FIG. 7 as Examples 2-3.

  In each Example, after the desmear treatment, all of the molten scattered Cu and the overhang were removed, and the measurement result of the outer layer copper foil etching width was 13 to 17 μm. In the evaluation of the reduction width of the outer layer copper foil thickness, the thickness after desmearing was reduced by 0.6 to 0.8 μm with respect to the thickness after laser via processing. In the evaluation of the reduction width of the inner layer wiring thickness, the thickness after desmearing was reduced by 0.4 to 0.5 μm with respect to the thickness after laser via processing.

  (C) Alkaline treatment liquid temperature in the direct via processing process was changed in the range of 30 to 80 ° C, and printed wiring board was produced in the same manner as in Example 1, and the molten and scattered Cu and overhangs were removed and the outer layer copper foil The etching width was measured, and the reduction width of the thickness of the outer layer copper foil and inner layer wiring was evaluated. The results are shown in FIG. Each alkali treatment condition is shown in FIG. 7 as Examples 4-5.

  In each example, after the desmear treatment, all of the molten scattered Cu and the overhang were removed, and the measurement result of the outer layer copper foil etching width was 14 to 18 μm. In the evaluation of the reduction width of the outer layer copper foil thickness, the thickness after desmear treatment was reduced by 0.5 to 0.6 μm with respect to the thickness after laser via processing. In the evaluation of the reduction width of the inner layer wiring thickness, the thickness after desmearing was reduced by 0.5 μm compared to the thickness after laser via processing.

  (C) The composition of the alkaline treatment liquid in the direct via processing process is potassium hydroxide, and a printed wiring board is produced in the same manner as in Example 1, and the measurement of the removal state of the molten scattered Cu and overhang and the outer layer copper foil etching width is performed. The reduction width evaluation of the thickness of outer layer copper foil and inner layer wiring was performed. The results are shown in FIG. The alkali treatment conditions are shown in FIG.

  After the desmear treatment, all of the molten splash Cu and overhangs were removed. The measurement result of the outer layer copper foil etching width was 16 μm. In the evaluation of the reduction width of the outer layer copper foil thickness, the thickness after desmearing was reduced by 0.8 μm compared to the thickness after laser via processing. In the evaluation of the reduction width of the inner layer wiring thickness, the thickness after desmearing was reduced by 0.5 μm compared to the thickness after laser via processing.

  Printed wiring board as in Example 1 with the composition of the (d) molten splash Cu etching solution in the direct via processing process as ferric chloride, ammonium persulfate, sodium persulfate, ammonia / hydrogen peroxide, ammonia / copper chloride The measurement of the removal state of the molten scattered Cu and the overhang and the etching width of the outer layer copper foil, and the evaluation of the reduction width of the thickness of the outer layer copper foil and the inner layer wiring were performed. The results are shown in FIG. Each melt-scattering Cu etching treatment condition is shown in FIG.

  In each Example, after the desmear treatment, all of the molten scattered Cu and the overhang were removed, and the measurement result of the outer layer copper foil etching width was 12 to 19 μm. In the evaluation of the reduction width of the outer layer copper foil thickness, the thickness after desmearing was reduced by 0.5 to 0.9 μm with respect to the thickness after laser via processing. In the evaluation of the reduction width of the inner layer wiring thickness, the thickness after desmearing was reduced by 0.4 to 0.5 μm with respect to the thickness after laser via processing.

  From the results of these Examples 1 to 11, in the printed wiring board manufacturing method, by using the direct via processing process of the present invention, the thickness reduction of the inner layer wiring is 0.5 μm or less, the thickness of the outer layer copper foil It is possible to remove molten spatter Cu and overhangs with a decrease width of 1.0 μm or less. Further, according to the present invention, a multilayer printed wiring board with high reliability of interlayer connection can be obtained by improving the shape of the laser via.

[Comparative Example 1]
For comparison, a multilayer printed wiring board was produced by performing the treatment under the same conditions as in Example 1 except that the alkali treatment was not performed.
(1) Copper foil surface oxidation treatment Blackening treatment was carried out in the same manner as in Example 1 in order to roughen the outer copper foil surface of the copper clad laminate and to form a copper oxide film.
(2) Laser via processing Next, the black via-treated copper clad laminate was subjected to blind via processing using a CO ₂ laser in the same manner as in Example 1.
(3) Melt scattered Cu etching process Next, an etching process was performed in the same manner as in Example 1 in order to remove the melt scattered Cu and the overhang.
(4) Desmearing treatment Next, desmearing treatment was performed in the same manner as in Example 1 in order to remove the resin residue on the via bottom.

  In the same manner as in Example 1, the cross-sectional observation was performed in order to investigate the reduction of the thickness of the outer layer copper foil and the inner layer wiring, the measurement of the outer layer copper foil and the inner layer wiring etching width, and the removal state of the molten scattered Cu and overhang in the produced printed wiring board. went. The samples were processed after laser via processing in the direct via processing process and after desmear processing. The results are shown in FIG.

  As a result of removing the molten splash Cu and overhang, the molten splash Cu and overhang remained after the desmear treatment. This is presumably because, because no alkali treatment was performed, deposits derived from the insulating layer remained on the surface of the melt-scattered Cu and the overhang portion during laser processing, and the etching solution was not touched. In the evaluation of the reduction width of the outer layer copper foil thickness, the thickness after desmearing was reduced by 0.5 μm compared to the thickness after laser via processing. In the evaluation of the reduction width of the inner layer wiring thickness, the thickness reduction after desmear processing was 0.5 μm compared to the thickness after laser via processing.

  Thus, if the alkali treatment is not performed before the melt-scattering Cu etching process, the melt-scattering Cu and the overhang cannot be completely removed.

[Comparative Example 2]
For comparison, a direct via processing process was performed under the same conditions as in Example 1 except that the molten scattering Cu etching solution was changed to a cupric chloride solution.
(1) Copper foil surface oxidation treatment Blackening treatment was carried out in the same manner as in Example 1 in order to roughen the outer copper foil surface of the copper clad laminate and to form a copper oxide film.
(2) Laser via processing Next, the black via-treated copper clad laminate was subjected to blind via processing using a CO ₂ laser in the same manner as in Example 1.
(3) Alkali treatment Next, alkali treatment was performed in the same manner as in Example 1 in order to remove deposits derived from the insulating layer generated on the via wall surface during laser processing.
(4) Melt scattered Cu etching process Next, an etching process was performed to remove the molten scattered Cu and the overhang. The etching solution was cupric chloride 100 g / l and the processing conditions were a solution temperature of 30 ° C., but the copper oxide film dissolved immediately after immersion in the etching solution.

  From this result, it was found that cupric chloride solution is not suitable for melt-sputtering Cu etching solution because it easily dissolves copper oxide. Therefore, the melt-sputtering Cu etching solution must have a low solubility of the copper oxide film.

[Comparative Example 3]
For comparison, the direct via processing process sequence was changed, and the oxide film removal process and the desmear process were followed by a melt-scattered Cu etching process to produce a multilayer printed wiring board similar to that of Example 1.
(1) Copper foil surface oxidation treatment First, a blackening treatment was performed under the same conditions as in Example 1 in order to roughen the outer copper foil surface of the copper-clad laminate and form a copper oxide film. It was.
(2) Laser via processing Next, blind via processing was performed on the copper-clad laminate subjected to blackening treatment using a CO ₂ laser under the same conditions as in Example 1.
(3) Copper oxide film removal process Next, the etching process was performed in order to remove the copper oxide film on an outer layer copper foil. The etching solution was 200 g / l ammonium persulfate and 5 ml / l sulfuric acid, and the treatment conditions were a solution temperature of 30 ° C. and a treatment time of 1 minute.
(4) Desmearing treatment Next, desmearing treatment was performed under the same conditions as in Example 1 in order to remove the resin residue at the bottom of the via.
(5) Melt scattered Cu etching process Next, an etching process was performed under the same conditions as in Example 1 in order to remove the melt scattered Cu and the overhang.

  In the same manner as in Example 1, the cross-sectional observation was performed in order to investigate the reduction of the thickness of the outer layer copper foil and the inner layer wiring, the measurement of the outer layer copper foil and the inner layer wiring etching width, and the removal state of the molten scattered Cu and overhang in the produced printed wiring board. went. The samples were processed after laser via processing in the direct via processing process and after melt-sputtered Cu etching processing. The results are shown in FIG.

  After the desmear treatment, all of the molten scattered Cu and overhang were removed, and the measurement result of the outer layer copper foil etching width was 3 μm. However, when the reduction width of the outer layer copper foil was evaluated, the thickness after the melt-sputtering Cu etching process was reduced by 2.5 μm with respect to the thickness after the laser via processing. In the evaluation of the reduction width of the inner layer wiring thickness, the thickness after the melt-sputtering Cu etching processing was reduced by 2.1 μm with respect to the thickness after the laser via processing. As described above, when the melt scattering Cu etching process is performed after the oxide film removal process and the desmear process, the thicknesses of the outer layer copper foil and the inner layer wiring are greatly reduced.

  From the results of these Comparative Examples 1 to 3, the necessity of alkali treatment in the direct via processing process of the present invention, the selectivity of the melt-sprayed Cu etching solution, and the importance of the process sequence were confirmed.

[Comparative Example 4]
Using the conventional large window method, a four-layer printed wiring board similar to that in Example 1 was manufactured, and the inner layer wiring thickness reduction width and the via misalignment evaluation were performed in the same manner as in Example 1.

  A part of the manufacturing process of the printed wiring board by the large window method is shown in FIG. The difference from the printed wiring board manufacturing process by direct via processing is that an oxide film is not formed on the outer layer copper foil before laser via processing, and the outer layer copper foil in the via forming portion is etched in advance. Therefore, no molten splash Cu and overhang are generated on the outer layer copper foil surface. The outer layer copper foil etching diameter was 180 μm, with the outer layer copper foil etching width being 40 μm with respect to the laser diameter of 100 μm.

  As shown in FIG. 8 (a), an outer layer copper foil resist pattern is formed on the four-layer copper clad laminate produced by performing the processes shown in FIGS. 3 (a) to 3 (d). ) Etch the outer layer copper foil in the via forming portion. Next, as shown in FIG. 8 (c), laser via processing was performed, and desmear processing was performed. Thereafter, an outer layer circuit was formed in the same manner as in FIGS. 3 (f) to 3 (h), and a four-layer printed wiring board was produced.

  FIG. 4 shows the reduction width of the inner layer wiring thickness and the via position deviation evaluation result in the manufactured four-layer printed wiring board. The decrease in inner layer wiring thickness was 0.5 μm, and the via misalignment rate was a maximum of 36%. Further, the land diameter Lr of the outer layer circuit is 280 μm.

  As described above, when the conventional large window method is used, after the pattern is formed in the outer layer copper foil in advance, the positional deviation between the outer layer circuit and the via is generated in order to process the via, and the positional deviation is corrected. The outer layer circuit land diameter is also increased.

Schematic showing a molten scattering Cu and overhang. Schematic showing a direct via processing process. Schematic showing a printed wiring board manufacturing process. The figure which shows the result of a molten scattering Cu removal state, the reduction | decrease rate of wiring thickness, and via position shift evaluation. Schematic showing the evaluation method of outer layer copper foil etching width. Schematic showing the evaluation method of an outer layer circuit and via position gap. The figure which shows a composition, density | concentration, and process conditions of an alkali process and a melt-scattering Cu etching process. Schematic showing the printed wiring board manufacturing process by the large window method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating layer 2 Inner layer wiring 3 Outer layer copper foil 4 Copper oxide film 5 Melt scattering Cu and overhang part 6 Deposit from an insulating layer 7 Inner layer base material 8 Resist 9 Copper plating film 10 Outer circuit

Claims (6)

In a method for manufacturing a printed wiring board in which blind via processing is directly performed on a copper foil using a laser on a copper clad laminate in which a copper foil is bonded to a base resin,
In the blind via processing step, an oxide film is formed on the surface of the copper foil, a laser via processing step, the insulating layer residue on the bottom of the via at the time of the laser via processing is left, and deposits derived from the insulating layer generated on the via wall surface A method for producing a printed wiring board, comprising performing an alkali treatment step to be removed , a melt-scattering Cu etching treatment step, and a desmear treatment step to remove a resin residue on a via bottom in this order.   The method for manufacturing a printed wiring board according to claim 1, wherein in the alkali treatment step, the treatment is performed with a treatment liquid containing sodium hydroxide or potassium hydroxide.   2. The printed wiring board manufacturing method according to claim 1, wherein in the melt-scattered Cu etching treatment step, a treatment solution containing ammonium persulfate, a treatment solution containing sodium persulfate, a treatment solution containing ferric chloride, A method for producing a printed wiring board, wherein the treatment is performed with a treatment liquid containing hydrogen oxide or a treatment liquid containing ammonia and copper chloride.   The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the decrease in inner layer wiring thickness before and after the formation of the laser via is 0.5 μm or less.   The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein a decrease in the thickness of the outer layer copper foil before and after the formation of the laser via is 1.0 μm or less. A printed wiring board manufactured by the method for manufacturing a printed wiring board according to claim 1,
Etching width of outer layer copper foil at the end of via is 20 μm or less, positional deviation rate between outer layer circuit and via is 5% or less, and decrease in inner layer wiring thickness at via is 0.5 μm or less Printed wiring board.

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