TWI442858B - Production method of printed wiring board - Google Patents

Description

Printed wiring board manufacturing method

The present invention relates to a method of manufacturing a printed wiring board in which a laser beam is formed by irradiating laser light onto a multilayer laminated plate formed by laminating a resin layer and a copper layer.

In recent years, miniaturization, high density, and high performance of electronic devices have required the formation of high-density circuits in printed wiring boards. In the multilayer printed wiring board which satisfies such a requirement, in order to form a layer indirectly, a through hole such as a blind via having a bottom hole or a through-hole via of a through hole is formed. At this time, in terms of processing efficiency and cost, most of the laser processing using a carbon dioxide gas laser is used as a means of opening.

Taking a conformal mask method as an example, a conventional method of forming a through hole by laser processing will be described with reference to the drawings. Referring to the third drawings A to C, there are shown sectional views of the steps of the conformal mask method.

First, a multilayer laminated board as shown in Fig. A is prepared. In the third figure A, the multi-layer laminate is used for: a glass fiber reinforced epoxy resin impregnated substrate (glass epoxy substrate), an arylamine fiber reinforced epoxy resin impregnated substrate (arylamine epoxy) a core material 1 having a copper layer 1b formed on both surfaces of an insulating base material 1a of a resin such as a substrate), and a resin comprising a prepreg containing glass reinforced fibers or other resin laminated on both surfaces of the core material 1 The layer 2 has a multilayered laminate in which copper foil 3 is laminated on the opposite side surface of the core material 1 in the individual resin layer 2. Usually, the copper layer 1b of the core material 1 is patterned to form a copper wiring.

Then, the portion 3a forming the through hole in the copper foil 3 on the surface side is removed by etching (third drawing B). Next, the resin layer 2 at a position directly under the portion 3a where the through holes are formed is opened by laser (third view C) to form a blind via hole BV.

On the other hand, in recent years, a direct laser method in which a laser is irradiated on a copper foil on the surface side and a copper foil and a resin layer are opened to form a through hole is also considered. In this direct laser method, since there is no need to etch the copper foil, there is no problem that copper remains due to poor etching, and the conformal mask of the above-mentioned conformal mask is also superior in circuit position matching accuracy between copper layers. Excellent method.

However, in either of the conformal reticle method and the direct laser method, the stain S of the resin layer 2 residue is generated on the inside of the through hole during the laser processing (third drawing C). When the plating treatment is performed in the through hole in which the stain S remains in this way, there is a possibility that the interlayer is not electrically connected.

Therefore, in the conventional through hole forming step, it is necessary to remove the stain removing step after the laser processing. For example, in the conventional stain removing step, after the laser-processed multi-layered laminate is subjected to a swelling treatment, it is further treated with a potassium permanganate solution, and further subjected to reduction and removal of potassium permanganate for neutralization treatment. In order to remove stains (for example, refer to Patent Documents 1 to 3 below). Further, in Patent Document 4 listed below, in order to improve the stain removal property, a stain removal step in which a potassium permanganate solution is treated and ultrasonic cleaning is combined is proposed.

However, the potassium permanganate used in the above-described stain removing step has a high possibility of causing environmental pollution, and it is difficult to handle the waste liquid because it is a strong oxidizing agent.

Therefore, Patent Document 5 listed below proposes a method of not using an oxidizing resin dissolving agent such as a potassium permanganate solution, that is, an organic swelling agent, and further combining ultrasonic cleaning to remove stains. The stain removal step.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 6-314869

[Patent Document 2] Japanese Patent Laid-Open No. 5-167924

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2007-129147

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2007-158238

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2003-338679

In the stain removal step described in Patent Document 5, the waste liquid treatment is easier than the stain removal step described in Patent Documents 1 to 4, but the stain removal effect is insufficient. Therefore, it is desired to have a method in which the waste liquid is easily handled and the stain removal effect can be sufficiently obtained.

The present invention provides a method for producing a printed wiring board which solves the above-mentioned problems, and is a method which is easy to treat waste liquid and which can sufficiently obtain a stain removing effect.

The method for producing a printed wiring board according to the present invention is a method of forming a via by irradiating laser light onto a multilayer laminated board formed by laminating a resin layer and a copper layer, and the method includes the following steps: irradiating a thunder a step of immersing the plurality of laminated sheets after the light irradiation in a swelling treatment step of the non-oxidizing swelling agent; a micro-etching treatment step of contacting the multilayer laminated sheet after the swelling treatment step with the microetching agent; and after the step of performing the micro-etching treatment Ultrasonic ultrasonic processing is applied in a state where the multilayer laminated plate is immersed in a liquid.

Further, the "copper" in the above invention may be composed of pure copper or may be composed of a copper alloy. In the present specification, "copper" means pure copper or a copper alloy.

In the method for producing a printed wiring board of the present invention, since a non-oxidizing swelling agent is used instead of an oxidizing resin such as a potassium permanganate solution, waste liquid treatment is facilitated. Further, since the swelling treatment step, the micro etching treatment step, and the ultrasonic treatment step are sequentially performed, the stain remaining in the inside of the through hole can be surely removed.

The present invention is a method for producing a printed wiring board which is suitable for forming a through hole by irradiating laser light onto a multilayer laminated plate formed by laminating a resin layer and a copper layer. The laser processing method is not particularly limited, and for example, a well-known processing method such as a conformal reticle method or a direct laser method can be used. Further, the through hole to be formed is not particularly limited. For example, it can be applied to a case where a known through hole such as a blind via hole or a through hole is formed. However, the blind via hole easily remains at the bottom of the through hole due to the stain. For the sake of this, the effect of the present invention is more effectively exerted.

Hereinafter, the case where the blind via hole is formed by the direct laser method to which the present invention is applied will be exemplified as an example of the present invention, and the application example will be described with reference to the drawings. Referring to the first drawings A and B and the second diagrams A to C, there are shown cross-sectional views for explaining the method of manufacturing a printed wiring board according to an example of the present invention. It is to be noted that the same components as those in the above-mentioned third drawings A to C are denoted by the same reference numerals, and their description will be omitted.

First, a multi-layer laminate (the first drawing A) of the same as the above-mentioned third drawing A is prepared. Then, a portion of the copper foil 3 on the surface side 3 in which the through holes are formed is irradiated with a laser to form a blind via BV (Fig. B). At this time, the stain S of the residue of the resin layer 2 is generated on the bottom (the bottom of the through hole) of the blind via hole BV. In addition, in order to reduce the reflection of the laser light before the laser irradiation, the deuteration treatment or the copper surface treatment described in Japanese Laid-Open Patent Publication No. 2007-129193 may be performed.

The laser used in the step of the first drawing B is not particularly limited, but from the viewpoint of processing efficiency and cost, a carbon dioxide gas laser is applied. The carbon dioxide gas laser uses a wavelength of 9.3 μm to 10.6 μm belonging to the infrared wavelength region. The processing energy can be appropriately selected depending on the thickness of the copper foil 3 on the surface layer side, etc. However, for example, one shot irradiation of 8 to 27 mJ may be performed to perform perforation. More preferably, it is possible to illuminate the second hair to a low processing energy of 2 to 5 mJ, thereby cleaning the copper surface of the bottom of the through hole. In this paper, the processing energy (J) of a carbon dioxide gas laser is calculated by dividing the power (W) required for processing by the number of frequencies (Hz). In addition, it is not necessary to perform two shots. Further, if necessary, three or more irradiations can be performed.

After the step of the first FIG. B, in order to improve the removability of the stain S, a swelling treatment step of immersing the multi-layer laminate in a non-oxidizing swell (not shown) is performed to make the stain S as the second Swelling as shown in Figure A. The non-oxidizing swelling agent is not particularly limited as long as it is non-oxidizing and can penetrate the resin to swell the resin. For example, an organic solvent obtained by combining N-methyl-2-pyrrolidone, butyl cellosolve, N,N-dimethylformamide, glycol, methyl ethyl ketone, acetone, or the like, alone or in combination, may be used. Dissolved in an alkaline solution. As the alkaline solution, an aqueous sodium hydroxide solution, an aqueous calcium hydroxide solution, an aqueous potassium hydroxide solution or the like can be used. Further, the aqueous sodium hydroxide solution may be used alone as a non-oxidative swelling agent. From the viewpoint of the swelling effect, it is preferred to dissolve the above-exemplified organic solvent in an aqueous solution of sodium hydroxide. Further, the pH of the non-oxidative swelling agent is, for example, about 8 to 14.

The treatment temperature in the aforementioned swelling treatment step is preferably from 35 ° C to 70 ° C, more preferably from 40 ° C to 50 ° C. If the treatment temperature is 35 ° C or higher, the swelling effect becomes high. On the other hand, if the treatment temperature is 70 ° C or lower, it is advantageous in terms of cost. The treatment time in the swelling treatment step is preferably from 10 seconds to 300 seconds, more preferably from 15 seconds to 60 seconds, from the viewpoint of the swelling effect. Further, it is preferred to provide a water washing step after the swelling treatment step and before the microetching treatment step described below.

After the swelling treatment step, a microetching treatment step of bringing the multilayer laminated sheet into contact with a microetching agent (not shown) is performed. Thereby, as shown in the second drawing B, only a small etching (microetching) is performed on the copper surface of the via hole bottom, so that the stain S remaining in the bottom of the via hole is in a free state. The microetching agent is not particularly limited as long as it can microetch the copper surface. However, when a microetching agent obtained by dissolving hydrogen peroxide and sulfuric acid in a solvent such as water is used, it is uniform. Micro-etching the bottom of the hole, so it is ideal. The method of contacting the multi-layer laminate with the microetching agent may be performed by dipping or spraying. However, if the microetching agent is sprayed on the surface of the multi-layered laminate having the through holes formed (the case of the second drawing B is the surface side). In the method of the copper foil 3), since the stain S can be sufficiently freed without excessively etching the through-hole bottom, it is preferable.

The amount of etching at the bottom of the via hole in the microetching treatment step is preferably 1 to 7 μm, more preferably 2 to 5 μm, in order to suppress excessive etching of the via hole bottom and to make the stain S free. The amount of etching of the bottom of the through hole is controlled within the above-mentioned appropriate range. For example, in the case of spraying treatment, the temperature of the microetching agent can be set to 20 ° C to 35 ° C, and the spraying pressure is set to 0.05 MPa to 0.3. MPa, the treatment time was set to 10 seconds to 120 seconds for spraying treatment. Further, the amount of etching described above can be obtained by observing the cross section of the through hole before and after the treatment.

In the case of the direct laser method, at the time of laser processing, there may be a protrusion formed by copper scattering on the surface of the copper foil 3 around the opening of the through hole, or a periphery of the opening of the through hole. There is a case where the burrs of copper are formed. When the copper plating treatment of the next step is performed without removing such scattered particles or burrs of copper, there is a possibility that a problem such as abnormal precipitation of the metal may occur. In this case, when a microetching agent containing hydrogen peroxide and sulfuric acid (hereinafter, simply referred to as "microetching agent") is used as the microetching agent, the microetching process of the via hole bottom can be performed simultaneously. Remove the scattered particles and burrs of copper. Hereinafter, a microetching agent suitable for the removal of scattered particles and burrs of copper will be described.

In the case of performing the spray micro-etching treatment step, the surface of the copper foil 3 in which the scattered particles and burrs of copper are present is often in contact with the microetching agent from the sprinkler, so that the microetching agent is often replaced. The state is also often in a state of being supplied with a fresh microetching agent.

On the other hand, since the inside of the through hole is a very narrow portion, the replacement of the microetching agent is small, so that it is expected to be in a state of being nearly immersed by the microetching agent.

Therefore, in order to prevent excessive etching of the copper layer 1b located in the inner layer of the via hole, a microetching agent having a slow etching rate of immersion can be used.

Preferably, the microetching agent that satisfies the above requirements is a microetching agent having a etching rate of 3 to 5 times that of the etching process, and more preferably 3.5 to 4 times of a microetching agent. By such a microetching agent, it is possible to suppress excessive etching of the via hole and to make the stain S free, and to improve the removal property of the scattered matter and the burr of the copper.

The etching rate in the spraying process is such that the pressure is set to a suitable pressure within the range of the spray pressure (0.05 to 0.3 MPa) which is normally set by the spraying treatment, and the microetching agent is maintained at a suitable temperature in the range of 20 to 35 ° C. Next, the speed at which etching is performed at a specified time (for example, 1 minute) is measured. On the other hand, the etching rate in the immersion treatment is immersed in a microetching agent having the same temperature as that of the spraying treatment, and the speed at which etching is performed at the same time as the measurement and comparison processing. Then, the etching rate of the spray treatment and the etching speed of the immersion treatment are compared. Further, the etching rate can be obtained by dividing the amount of reduction in copper weight before and after etching in the micro-etching of the electrolytic copper foil by the etching time.

In order to make the etching rate in the spraying process 3 to 5 times the etching rate in the immersion treatment, for example, various additives such as a surfactant may be blended in the microetching agent. Specifically, an aliphatic or alicyclic amine, an alcohol, a tetrazole compound, a methyl ester compound, a nonionic surfactant, or the like can be blended.

The above aliphatic amine is preferably an aliphatic amine having 1 to 12 carbon atoms, and specific examples thereof include, for example, tri-n-butylamine, ethylenediamine, 2-ethylhexylamine, and the like.

Specific examples of the above alicyclic amine are, for example, cyclohexylamine, dicyclohexylamine, and the like.

Specific examples of the above alcohols include, for example, glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and tripropylene glycol.

Specific examples of the above tetrazole compound are, for example, 1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-mercapto-1H-tetrazole, and 1 -Methyl-5-ethyl-1H-tetrazole, and the like.

Specific examples of the methyl ester compound described above include, for example, ethyl acetate, isopropyl acetate, and butyl acetate.

Specific examples of the above nonionic surfactant are, for example, propylene glycol anhydride, polyethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and diethylene glycol single Ethyl ether and the like.

The above-exemplified additives may be appropriately selected from one type or two types or more. For example, in terms of the etching rate in the accelerated spraying treatment, one or more kinds selected from the group consisting of aliphatic amines, alicyclic amines, alcohols, methyl ester compounds, and nonionic surfactants may be blended. On the other hand, in terms of slowing the etching rate in the immersion treatment, a tetrazole compound can be blended. In particular, when the tetrazole compound and the alicyclic amine are used together, the over-etching of the via hole bottom can be effectively suppressed, and the removal of the scattered matter and the burr of the copper can be further improved, and the micro-etching can be more uniformly performed. The bottom of the hole is so ideal. The amount of these additives to be used is not particularly limited, but is preferably 0.001 to 2% by weight, and more preferably 0.01 to 0.5% by weight based on the total amount of the microetching agent.

In the case of a microetching agent having a relatively high removal property of copper and a burr, it is preferred that the concentration of hydrogen peroxide in the microetching agent be 1 to 15% by weight, more preferably 2 to 10% by weight. More preferably, it is 2 to 5% by weight.

Further, in the case of a microetching agent having a relatively high removal property of copper and a burr, it is preferable that the sulfuric acid concentration in the microetching agent is 3 to 25% by weight, more preferably 5 to 20% by weight. More preferably, it is 6 to 10% by weight.

After the micro-etching treatment step, the multi-layered laminate is immersed in a liquid (not shown), and an ultrasonic wave treatment step of applying ultrasonic waves is performed, thereby removing the stain S which is free from the bottom of the through-hole ( Figure II). The liquid used in such an ultrasonic treatment step can be suitably used as long as it is an acid-soluble liquid, an alkaline solution, or a liquid such as water. However, in the case of using water, it is safe and easy to manage. So it is especially ideal.

The condition for applying ultrasonic waves, for example, when water (temperature: 10 to 70 ° C) is used, is preferably applied at 28 kHz to 45 kHz for 10 seconds to 300 seconds, more preferably at 28 kHz to 45 kHz for 20 seconds to 300 seconds. . If the number of frequencies is within the above range, the removal of the stain S can be increased without damaging the substrate. Further, if the application time is within the above range, not only the stain S can be surely removed, but also the production efficiency can be increased.

Although the step of arranging the steps of the multi-layer laminated board after the ultrasonic treatment is omitted, for example, by plating copper on the inner wall of the through hole, the upper and lower copper foils 3 can be further patterned to form copper wiring. Multi-layer printed wiring board.

[Examples]

Hereinafter, the present invention will be further illustrated by exemplifying the embodiments and comparative examples in order to facilitate the understanding of the present invention. However, the present invention is not limited to the embodiments.

R-1766 manufactured by Matsushita Electric Works was used as a core material in which a copper layer was formed on both surfaces of an insulating substrate, and a prepreg (R1661ED manufactured by Matsushita Electric Works) having a thickness of 60 μm was laminated on both surfaces of the core material. On the opposite side to the core material of each prepreg, a copper foil (3EC-III manufactured by Mitsui Mining and Mining Co., Ltd.) having a thickness of 12 μm was laminated to form a multilayered laminate as shown in Fig. A. However, since it was a test substrate, neither of the outer layer and the inner layer was patterned (the wiring was not formed), but the treatment as shown below was performed.

First, the copper foil on the surface side of the test substrate was etched by a sulfuric acid/hydrogen peroxide-based laser processing pretreatment agent (MEC V bon d manufactured by MEC Co., Ltd.) to make the thickness of the copper foil on the surface layer side. It becomes 9.6 μm. By performing such laser processing pre-processing, laser processing can be performed with low energy.

Next, a through hole was formed under the following processing conditions using a carbon dioxide gas laser (LC-2G212/2C manufactured by Hitachi, Ltd.) so that the diameter of the laser irradiation side (surface side) was 100 μm, and the bottom surface side was The diameter is from 80 μm to 100 μm. In addition, before and after "/" in the conditions described below, the conditions of the first shot and the second shot in the case of performing two shots of laser irradiation are respectively shown.

(laser processing conditions)

Number of hair: 2 rounds

Frequency number: 1000Hz

Processing energy: 17.75mJ/3.60mJ

Pulse amplitude: 36μs/10μs

Next, the laser-treated test substrate was processed in the order of the swelling treatment step, the micro etching treatment step, and the ultrasonic treatment step in accordance with the conditions shown in Tables 1 and 2. Any of the swelling treatment steps are treated by dipping; any of the microetching treatment steps is performed by spraying. However, in the microetching process of Comparative Example 4, an etchant for circuit formation was used instead of the microetching agent, and the film was processed by spraying. Further, a water washing step is provided between the swelling treatment step and the micro etching treatment step. In addition, in the ultrasonic processing step, the ULTRASONIC CLEANER VS-100III manufactured by Sakae Shillai was used as the ultrasonic cleaner, and the test substrate was immersed in ion exchange water at a temperature of 25 ° C, according to Table 1 and Table 2. Ultrasonic waves are applied to the conditions shown.

Next, in order to facilitate the confirmation of the stain, the bottom of the through hole of the treated test substrate was subjected to platinum vapor deposition. Then, the cut surface of the through hole bottom was observed by a field emission scanning electron microscope FE-SEM (JSM-7000F manufactured by JEOL Ltd.) at a magnification of 3500 times, and the stain remaining in the bottom of the through hole was measured. The maximum value of the length L (refer to the third figure C). At this time, in each of the examples and the comparative examples, the maximum value was measured for each of the five through holes, and the average value of the maximum values was calculated. With respect to the above average value obtained, the stain removal property was evaluated in accordance with the following criteria.

(Evaluation criteria for stain removal)

The aforementioned average value is less than 2 μm: ◎

The aforementioned average value is 2 μm or more but less than 15 μm: ○

The aforementioned average value is 15 μm or more but less than 30 μm: △

The aforementioned average value is 30 μm or more: ╳

Table 1

Table 2

As shown in Tables 1 and 2, the stain removal properties of any of Examples 1 to 15 were higher than those of Comparative Examples 1 to 4.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and the equivalent technical changes of the present invention and the contents of the drawings are included in the scope of protection of the present invention. Within, combined with Chen Ming.

1. . . Core

1a. . . Insulating substrate

1b. . . Copper layer

2. . . Resin layer

3. . . Copper foil

3a. . . a portion forming a through hole

BV. . . Blind through hole

S. . . Stains

First, FIGS. A and B are cross-sectional views showing respective steps for explaining an example of a method of manufacturing a printed wiring board of the present invention.

FIGS. 2A to 4C are cross-sectional views showing respective steps for explaining an example of a method of manufacturing a printed wiring board of the present invention.

3A to C are cross-sectional views showing the steps of the conformal mask method.

1. . . Core

1a. . . Insulating substrate

1b. . . Copper layer

2. . . Resin layer

3. . . Copper foil

BV. . . Blind through hole

S. . . Stains

Claims (6)

A method of producing a printed wiring board, which is a method of manufacturing a printed wiring board in which a laser beam is formed by irradiating laser light to a multilayer laminated board formed by laminating a resin layer and a copper layer, wherein the method includes irradiating a swelling treatment step of immersing the multilayer laminated plate after laser light in a non-oxidizing swell; a micro-etching step of contacting the multilayer laminated plate after the swelling treatment step with a micro etchant; after the step of micro-etching An ultrasonic treatment step of applying ultrasonic waves in a state where the multilayer laminated plate is immersed in a liquid; and an oxidizing resin dissolving agent is not used, but the swelling treatment step, the micro etching processing step, and the ultrasonic processing step described above are used. To remove stains. The method of manufacturing a printed wiring board according to claim 1, wherein the microetching agent comprises a microetching agent of hydrogen peroxide and sulfuric acid. The method for producing a printed wiring board according to claim 2, wherein the microetching agent further contains a tetrazole compound and an alicyclic amine. The method of manufacturing a printed wiring board according to claim 1, wherein the micro-etching step is a step of spraying a micro-etching agent on a surface of the multi-layered laminate on which the through holes have been formed. The method for producing a printed wiring board according to the first aspect of the invention, wherein the non-oxidizing swelling agent is an alkaline solution containing an organic solvent or an aqueous sodium hydroxide solution. The method of manufacturing a printed wiring board according to any one of claims 1 to 5, wherein the ultrasonic processing step is a step of applying an ultrasonic wave in a state where the multilayer laminated plate is immersed in water.