JP6261104B1 - Method for manufacturing printed circuit board - Google Patents

Abstract

Provided is a printed circuit board manufacturing method capable of forming a through hole having an extremely small diameter with high processing accuracy, without deterioration in quality, and with low production cost and high production efficiency. SOLUTION: On both sides of a printed circuit board material 1 having a copper layer 1b on both sides of an insulating substrate 1a, the copper layer has a first opening 2a for forming an opening including an opening having a very small diameter. A step of forming the first resist mask 2, a step of etching the copper layer exposed from the first opening to expose the insulating base, a step of removing the first resist mask, a printed circuit board Forming a second resist mask 3 having a second opening 3a slightly larger than the first opening on both surfaces of the material, copper exposed from the second resist mask and the second opening; Forming a through hole 1a-2 by blasting the insulating base material exposed from the opening 1b-1 of the copper layer using the layer as a blasting mask, and removing the second resist mask Including. [Selection] Figure 1

Description

  The present invention relates to a method of manufacturing a printed circuit board having a through hole with a very small diameter.

As electronic devices become more advanced, smaller, and thinner, there is a need for smaller semiconductor packages, higher pin counts, and finer pitches for external terminals, and the demand for high-density wiring boards is increasing. It has become. For this reason, LSI (large scale integration) is directly mounted on a printed circuit board, or CSP (Chip Size Package) and BGA (Ball Grid Array) are mounted on a printed circuit board. .
Further, in order to cope with the higher density of printed circuit boards, there are increasing demands for finer wiring pitches and minimization of through-hole diameters for interlayer connections and the like.
Conventionally, the formation of a through hole with a very small diameter in a printed circuit board is usually performed by etching a copper layer on one side of the copper layer provided on both sides of the insulating base material in the printed circuit board material to provide a small diameter opening, The insulating base material exposed from the opening of the copper layer is formed by forming through holes one by one by laser processing (see, for example, Patent Document 1 below).

JP 2012-235176 A

  However, if through holes are formed one by one by laser processing, processing time is required when manufacturing printed circuit boards arranged in multiple rows, or when it is necessary to make a large number of through holes on one printed circuit board. It takes a long time, resulting in poor productivity and high cost. In addition, when a through hole having an extremely small diameter is formed by laser processing, the processed end surface may be carbonized and have conductivity.

Conventionally, as other methods for forming a through hole in a printed circuit board, a drilling method, a router processing method, a press processing method, and the like are known.
However, the method using drilling or router processing, like the laser processing method, forms through holes one by one, so that productivity is poor. In addition, in order to form a through hole having a very small diameter, it is necessary to use a drill or router having a minimized diameter. However, if the diameter of the drill or the router is small, the possibility of breakage or breakage increases. In addition, in drilling or router processing, the rotating drill or router is likely to be shaken by vibration, so it is difficult to process a through hole with a very small diameter with high accuracy. In the present application, the “minimum diameter” is generally about 50 μm or less and mainly refers to the size of the diameter of the through hole of φ20 to φ40 μm.

  In addition, the precision mold used for press working is expensive, and a separate precision mold corresponding to each different size and position of the through hole is required. For this reason, if a through hole having a very small diameter is formed by pressing, enormous manufacturing costs are required. In addition, there is a high possibility that the mold part for forming the extremely small diameter through hole is broken or damaged.

  The present invention has been made in view of the above problems, and provides a printed circuit board manufacturing method capable of forming a through hole having a very small diameter with high processing accuracy, without deterioration in quality, and with low production costs. The purpose is to do.

In order to achieve the above object, a printed circuit board manufacturing method according to the present invention includes a step of preparing a printed circuit board material having a copper layer on both surfaces of an insulating base material, and a first resist layer is formed on both surfaces of the printed circuit board material. Then, a first resist mask having a first opening for forming an opening having a predetermined diameter is formed in the copper layer on both sides of the printed circuit board material at a predetermined position. Process,
Etching and removing the copper layer at a portion exposed from the first opening of the first resist mask to expose the insulating substrate; and A step of removing, a second resist layer is formed on both sides of the printed circuit board material, and the first opening of the first resist mask has a diameter larger than that of the first opening. A step of forming a second resist mask having a slightly larger second opening, and the second resist mask and the portion of the second resist mask exposed from the second opening. Using the copper layer as a blasting mask, the step of blasting the insulating base material in the portion exposed from the opening of the copper layer to form a through hole; and removing the second resist mask It is characterized by comprising to step.

  In the printed circuit board manufacturing method of the present invention, the second resist layer used for forming the second resist mask is thicker than the first resist layer used for forming the first resist mask. Is preferably used.

  In the printed circuit board manufacturing method of the present invention, the etching substrate used for the etching process for exposing the insulating base material between the step of exposing the insulating base material and the step of removing the first resist mask. The first resist mask is further used as a blasting mask, and blasting is performed on the insulating base material at a portion exposed from the first opening and the copper layer opening of the first resist mask. It is preferable to include the process of forming a recessed part by giving.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the printed circuit board which can form a through-hole of a very small diameter with sufficient processing accuracy, without deterioration of quality, suppressing cost, and producing efficiency is obtained.

It is explanatory drawing which shows an example of the manufacturing process of the printed circuit board concerning 1st Embodiment of this invention. It is explanatory drawing which shows an example of the manufacturing process of the printed circuit board concerning 2nd Embodiment of this invention. It is explanatory drawing which shows an example of the manufacturing process of the printed circuit board concerning a comparative example.

Prior to the description of the embodiments, the process of deriving the printed circuit board manufacturing method of the present invention and the effects thereof will be described.
As described above, conventionally, there is a method for forming a through hole with a minimum diameter in a printed circuit board by etching a copper layer to provide a minimum diameter opening and laser processing the exposed insulating base material. There is a problem that it takes a long time, the productivity is poor and the cost is high, and the processed end face is carbonized to have conductivity. Other methods for forming through holes include drilling and router processing, and press processing. In addition to poor productivity, drilling and router processing methods include drilling and router processing. There are problems with router bending, breakage, and processing accuracy, and the press method has problems such as the cost of the mold and the risk of bending or breakage of the mold part for forming a through hole with a very small diameter. .

Here, the present inventor conceived, studied and studied the idea of using blasting for forming a through hole having a very small diameter with respect to an insulating base material.
Blasting is a processing method in which only the processing target portion in the printed circuit board material is covered with a resist mask so that the substrate is removed at high speed by spraying fine abrasive grains with compressed air.
When the present inventor compared with other processing methods, the blast processing has no carbonization of the processed surface unlike the laser processing, and unlike the drill processing, the through hole with a very small diameter can be processed with high accuracy. It has been found that a plurality of through-holes can be formed simultaneously, and, unlike press processing, the degree of freedom in design is wide and the manufacturing cost can be reduced.
More specifically, if the formation of an extremely small diameter through hole in the insulating base material is performed by blasting, the processed end face in the case of forming an extremely small diameter through hole by laser processing has carbonization and becomes conductive. There is no fear of it. In addition, since a plurality of through holes can be formed at the same time, productivity is high and costs can be reduced.
In addition, when forming a through hole with a very small diameter by drilling or router processing, there is no risk of the drill or router being broken or damaged, and the rotating drill or router will not be eccentric due to vibration. It is easy to process holes with high accuracy.
In addition, there is no risk of bending or breakage of the mold part when forming a through hole having a very small diameter by press working, and a separate precision mold corresponding to each different size and position of the through hole is not required.

Further, as a result of further studies by the present inventor, it has also been found that there are the following problems when blasting is used to form a through hole having a very small diameter.
In the blasting process, fine abrasive grains are ejected at high speed with compressed air to the printed circuit board material on which a resist mask is formed in a part other than the processing target, and the printed circuit board material in the processing target part is removed. As a result of the collision with the resist mask, the resist mask is scraped off together with the printed circuit board material on the exposed surface. For this reason, if the spraying time of the fine abrasive grains is extended for a long time, the printed circuit board material covered with the resist mask is exposed and scraped off by the collision of the fine abrasive grains, resulting in a product as a printed circuit board. There is a risk that the quality of the.
In blasting, as a measure for forming a through hole with a very small diameter without exposing the part covered with the resist mask, the layer thickness of the resist layer used for the resist mask to be formed in a part other than the processing target is It is possible to increase the thickness.
However, increasing the thickness of the resist layer decreases the processing accuracy of the mask shape formed on the resist layer through exposure and development and the reliability of mask formation, and as a result, the extremely small diameter penetration formed by blast processing. Hole machining accuracy and yield are reduced.

  In view of such problems in each processing method, the present inventors have manufactured a printed circuit board for forming a through hole having a very small diameter with respect to a printed circuit board material having copper layers on both sides of an insulating base material. As a result of repeated trial and error regarding the method, the present invention has been derived.

The method for producing a printed board according to the present invention includes a step of preparing a printed board material having a copper layer on both sides of an insulating base, a first resist layer is formed on both sides of the printed board material, and a predetermined position of the printed board material Forming a first resist mask having a first opening for forming an opening having a predetermined diameter, including an opening having an extremely small diameter in the copper layers on both sides of the first and second layers; The copper layer in the portion exposed from the opening of 1 is etched and removed by etching to expose the insulating base, the step of removing the first resist mask, and the both sides of the printed circuit board material. A second resist mask having a second opening having a diameter slightly larger than the first opening at a position where the second resist layer is formed and the first opening of the first resist mask is formed Forming the step and Using the second resist mask and the copper layer in the portion exposed from the second opening of the second resist mask as a blasting mask, the insulating substrate in the portion exposed from the opening in the copper layer And blasting to form a through hole, and removing the second resist mask.
If the through hole is formed on the insulating base material by blasting as in the printed circuit board manufacturing method of the present invention, the machining end face is carbonized when forming a through hole with an extremely small diameter by laser processing. There is no risk of having conductivity. In addition, since a plurality of through holes can be formed at the same time, productivity is high and costs can be reduced.
In addition, when forming a through hole with a very small diameter by drilling or router processing, there is no risk of the drill or router being broken or damaged, and the rotating drill or router will not be eccentric due to vibration. It is easy to process holes with high accuracy.
In addition, there is no risk of bending or breakage of the mold part when forming a through hole having a very small diameter by press working, and a separate precision mold corresponding to each different size and position of the through hole is not required.

Further, as in the method of manufacturing a printed circuit board according to the present invention, the first resist mask having the first opening is formed, and the copper in the portion exposed from the first opening of the first resist mask is formed. If the layer is etched and removed to expose the insulating substrate, an opening having a very small diameter is formed in the copper layer in the first resist layer used for forming the first resist mask. Therefore, the minimum necessary thickness can be used. The thinner the thickness of the first resist layer used for forming the first resist mask, the higher the processing accuracy of the first opening of the first resist mask formed through exposure and development. However, the first resist layer used for forming the first resist mask has a layer thickness that is the minimum necessary for forming an opening having a very small diameter in the copper layer. The processing accuracy of the first opening of the first resist mask formed through the process is remarkably increased. As a result, the processing accuracy of the opening portion of the copper layer formed by etching and removing the copper layer in the portion exposed from the first opening portion with high processing accuracy is remarkably increased.
And like the manufacturing method of the printed circuit board of this invention, it has a 2nd opening part with a diameter slightly larger than a 1st opening part in the position which formed the 1st opening part of the 1st resist mask. Forming a second resist mask, and using the copper layer in the portion exposed from the second opening of the second resist mask and the second resist mask as a blasting mask, the opening of the copper layer If the insulating base in the exposed part is subjected to blasting, the through hole is formed in the insulating base through the opening of the copper layer processed with high precision, and the copper layer Since it is thin, the processing accuracy of the through hole of the insulating base formed by blast processing is remarkably increased. Further, the portion around the opening in the copper layer used as a blasting mask at the time of blasting is slightly smaller in diameter than the first opening at the position where the first opening of the first resist mask is formed. It is protected by a second resist mask having a large second opening. As a result, the portion around the opening in the copper layer does not have to be scraped into fine abrasive grains during blasting, and the processing accuracy of the through-hole formed in the insulating base material is kept high.

In the method for manufacturing a printed circuit board according to the present invention, preferably, the second resist layer used for forming the second resist mask has a layer thickness larger than that of the first resist layer used for forming the first resist mask. Use a thicker one.
As described above, the processing accuracy of the first opening of the first resist mask formed through exposure and development improves as the thickness of the first resist layer used for forming the first resist mask decreases. And the processing precision of the opening part of the copper layer formed by performing an etching process to the copper layer in the site | part exposed from the 1st opening part and melt | dissolving and removing improves.
On the other hand, the second resist mask is used to protect a copper layer used as a blasting mask during blasting. For this reason, the layer thickness of the second resist layer used for forming the second resist mask is made thick so that the portion covered with the second resist mask is removed by blasting and the copper layer is not exposed. It is desirable to do.
However, if the second resist layer used for forming the second resist mask is thicker than the first resist layer used for forming the first resist mask, the first resist is used. It becomes easy to improve the processing accuracy of the opening of the copper layer through the mask, and the portion covered with the second resist mask is scraped off at the time of blasting through the second resist mask. It becomes easy to protect the copper layer without exposing.

In the printed circuit board manufacturing method of the present invention, it is preferable that the first etching process used to expose the insulating base material between the step of exposing the insulating base material and the step of removing the first resist mask. 1 is further used as a blasting mask, and the insulating substrate in the part exposed from the first opening of the first resist mask and the opening of the copper layer is subjected to blasting to form a recess. A step of forming is included.
In this manner, the first resist mask is further used as a blasting mask, and the recess is formed by blasting the insulating substrate in the portion exposed from the first opening and the opening of the copper layer. Then, the insulating substrate at the site to be removed in the blasting process using the second resist mask and the copper layer in the site exposed from the second opening of the second resist mask as a blasting mask Can reduce the thickness. As a result, a thin resist layer can be used as the second resist layer used for forming the second resist mask, and the cost can be reduced accordingly. Further, it is possible to reduce the collision amount of fine abrasive grains at the time of blasting to the portion around the opening in the copper layer slightly exposed from the second opening of the second resist mask, and to achieve higher accuracy. A through hole can be formed.

  In the printed circuit board manufacturing method of the present invention, preferably, if blasting is performed simultaneously from both sides of the printed circuit board material, the blasting time can be greatly shortened.

  Therefore, according to the present invention, it is possible to obtain a printed circuit board manufacturing method capable of forming a through hole having an extremely small diameter with high processing accuracy, without deterioration in quality, and with low production cost and high production efficiency.

Next, an embodiment of the present invention will be described.
First Embodiment FIG. 1 is an explanatory view showing an example of a manufacturing process of a printed circuit board according to a first embodiment of the present invention.
In the manufacturing method of the present embodiment, a printed circuit board having a through hole with a very small diameter is manufactured by the following steps.
Note that description of pre-processing and post-processing including chemical solution cleaning, water cleaning, and the like, which are performed in the following manufacturing steps, is omitted for convenience.
First, a printed circuit board material 1 having a copper layer 1b on both surfaces of an insulating base 1a is prepared (see FIG. 1 (a)).
As the insulating base material 1a, an epoxy resin, a phenol resin, a polyimide resin, a fluorine-containing resin, a polyester resin, a polyphenylene oxide resin, or the like, or a mixture of a plurality of resins can be used. Moreover, what further mix | blended various additives and softening agents, and what used organic fibers, such as inorganic fibers, such as glass, a polyester resin, a polyimide resin, and various natural fibers, can also be used as a reinforcing material.

  Next, the first dry film resist 2 'having a predetermined thickness determined by the thickness of the copper layer 1b to be processed and the minimum opening diameter (here, the diameter of the extremely small through hole) is formed on both surfaces of the printed board material 1. Laminate (see Fig. 1 (b)). The type of the first dry film resist 2 ′ is not particularly limited, but usually a negative type that cures the photosensitive portion is used. In addition, a positive type dry film resist may be used. Alternatively, a liquid photoresist may be applied.

Next, an opening pattern having a predetermined diameter including at least one opening pattern having a minimum diameter of, for example, φ30 μm is exposed at a predetermined portion of the first dry film resist 2 ′ on both sides.
Next, it develops and the 1st resist mask 2 which has each 1st opening part 2a on both surfaces of the printed circuit board material 1 is formed (refer FIG.1 (c)).

  Next, the copper layer 1b in the part exposed from the first opening 2a of the first resist mask 2 on both sides is etched to remove the copper layer 1b, and the insulating base 1a is exposed in the removed part. (See FIG. 1 (d)). At this time, an opening 1b-1 is formed in the copper layer 1b.

  Next, the first resist mask 2 is peeled off (see FIG. 1 (e)).

  Next, a predetermined thickness determined by an opening diameter that is slightly larger than the thickness of the insulating base material 1a to be processed and the minimum opening diameter (here, the diameter of a through hole having a minimum diameter of 30 μm) is provided on both surfaces of the printed circuit board material 1. A second resist layer 3 ′ is formed (see FIG. 1 (f)). The insulating base material 1a has a larger thickness than the copper layer 1b. For this reason, the second resist layer 3 ′ is thicker than the first dry film resist 2 ′.

  Next, an opening pattern having a diameter slightly larger than that of the first opening is exposed at a position where the first opening 2a of the first resist mask 2 is formed in the second resist layer 3 ′ on both sides. .

  Next, development is performed and second diameters slightly larger than the first openings 2a are formed at positions where the first openings 2a of the respective first resist masks 2 are formed on both surfaces of the printed circuit board material 1. The second resist mask 3 having the opening 3a is formed (see FIG. 1G).

  Next, the thickness of the insulating substrate 1a to be processed using the second resist mask 3 and the copper layer 1b in the portion exposed from the second opening 3 of the second resist mask 3 as a blasting mask. The slit nozzle is appropriately moved with a predetermined pressure and a predetermined injection amount, using blasting abrasive grains having a predetermined abrasive grain size determined by the thickness and the minimum opening diameter (here, the diameter of the through-hole having a very small diameter). While blasting abrasive grains are sprayed, blasting is performed from one side of the printed circuit board material 1, and the insulating base 1a in the portion exposed from the opening 1b-1 of the copper layer 1b is approximately half the thickness. The pit is dug to form a recess 1a-1 (see FIG. 1 (h)).

  Next, blasting is performed from the other side of the printed circuit board material 1 in the same manner as one side, and the insulating base 1a is dug to penetrate the bottom surface of the recess 1a-1 (see FIG. 1 (i)). Thereby, the through-hole 1a-2 of a predetermined diameter including the through-hole of the minimum diameter is formed in the insulating base material 1a.

  Next, the second resist mask 3 is peeled off (see FIG. 1 (j)). Thereby, the printed circuit board material 1 in which the through-hole 1-1 of the predetermined diameter including the through-hole of the minimum diameter which penetrates the insulating base material 1a and the copper images 1a on both sides is formed is obtained.

Next, a wiring pattern is formed. Specifically, first, a conductor is formed by performing through-hole plating or via fill plating on the through-hole 1-1 formed in the printed circuit board material 1 to perform interlayer connection (not shown). Next, a third dry film resist is laminated on both surfaces of the printed circuit board material 1, and a third pattern for forming a wiring pattern by the copper layer 1 b is formed using the same formation method as the first resist mask 2. A resist mask is formed (not shown). Next, the copper layer 1b exposed from the third resist mask is etched to form a predetermined wiring pattern (not shown). Thereafter, the third resist mask is removed (not shown).
Thereby, the through hole is conducted, and the printed board on which the wiring is formed is completed.

According to the printed circuit board manufacturing method of the present embodiment, the first resist mask 2 having the first opening 2 a is formed and exposed from the first opening 2 a of the first resist mask 2. Since the insulating layer 1a is exposed by etching the copper layer 1b at the site so as to be dissolved and removed, the dry film resist 2 ′ used for forming the first resist mask 2 is used. The thing of minimum thickness required in order to form the very small diameter opening part in the copper layer 1b can be used. The thinner the film thickness of the dry film resist 2 ′ used for forming the first resist mask 2, the higher the processing accuracy of the first opening 2 a of the first resist mask 2 formed through exposure and development. However, the dry film resist 2 ′ used for forming the first resist mask 2 has a layer thickness that is the minimum necessary for forming a very small diameter opening in the copper layer 1b, thereby allowing exposure and development. The processing accuracy of the first opening 2a of the first resist mask 2 formed after that is remarkably increased. As a result, the processing accuracy of the opening of the copper layer 1b formed by etching and removing the copper layer 1b in the portion exposed from the first opening 2a with high processing accuracy is remarkably high. Become.
Then, according to the printed circuit board manufacturing method of the present embodiment, the second resist film 2 is slightly larger in diameter than the first opening 2a at the position where the first opening 2a of the first resist mask 2 is formed. A second resist mask 3 having an opening 3a is formed, and the second resist mask 3 and the copper layer 1b exposed from the second opening 3a of the second resist mask 3 are for blasting. Since it used as a mask and blasted to the insulating base material 1a in the site | part exposed from the opening part 1b-1 of the copper layer 1b, formation of the through-hole 1a-2 with respect to the insulating base material 1a is high. Since the copper layer 1b is thin through the opening 1b-1 of the copper layer 1b processed with high accuracy, the processing accuracy of the through hole 1a-2 of the insulating base 1a formed by blasting is high. It will be much higher. Further, a portion around the opening 1b-1 in the copper layer 1b used as a blasting mask at the time of blasting has a first diameter at a position where the first opening 2a of the first resist mask 2 is formed. It is protected by a second resist mask 3 having a second opening 3a that is slightly larger than the opening 2a. As a result, the portion around the opening 1b-1 in the copper layer 1b does not have to be scraped into fine abrasive grains during blasting, and the processing accuracy of the through hole 1a-2 formed in the insulating base 1a is kept high. Be drunk.

  Further, according to the method of manufacturing a printed circuit board of the present embodiment, the dry resist resist 2 ′ used for forming the first resist mask 2 is formed on the second resist layer 3 ′ used for forming the second resist mask 3. As a result, the processing accuracy of the opening 1b-1 of the copper layer 1b can be easily improved through the first resist mask 2, and the second resist mask 3 is used. During the blasting process, the portion covered with the second resist mask 3 is scraped off, and the copper layer 1b is easily protected without exposing the copper layer 1b.

  In the printed circuit board manufacturing method of the present embodiment, if blasting is performed simultaneously from both sides of the printed circuit board material 1, the blasting time can be greatly shortened.

Second Embodiment FIG. 2 is an explanatory view showing an example of a manufacturing process of a printed circuit board according to a second embodiment of the present invention.
In the manufacturing method of the present embodiment, as in the first embodiment, the preparation of the printed circuit board material 1 (see FIG. 2A), the laminate of the first dry film resist 2 ′ (see FIG. 2B), After forming the first resist mask 2 (see FIG. 2 (c)) and exposing the insulating base 1a (see FIG. 2 (d1)) by forming the opening 1b-1 of the copper layer 1b, the insulating group is formed. Using the first resist mask 2 used for the etching process that exposes the material 1a as a blasting mask, the thickness of the insulating substrate 1a to be processed is within a range where the first resist mask 2 is not removed. And using a blasting abrasive grain having a predetermined abrasive grain size determined by the minimum opening diameter (here, φ20 μm as the diameter of the extremely small through hole), the slit nozzle at a predetermined pressure and a predetermined injection amount. Abrasive grains for blasting while moving appropriately The insulating substrate 1a at the part exposed from the first opening 2a of the first resist mask 2 and the opening 1b-1 of the copper layer 1b. Are dug by approximately a quarter of the thickness from both sides to form the recesses 1a-1 ′ and 1a-2 ′ (see FIG. 2 (d2)). In addition, you may perform the blast process for forming recessed part 1a-1 ', 1a-2' for each one side of the printed circuit board material 1. FIG.
Thereafter, as in the first embodiment, the first resist mask 2 is stripped (see FIG. 2E), the second resist layer 3 ′ is formed (see FIG. 2F), and the diameter is the first. Formation of the second resist mask 3 having a second opening 3a slightly larger than the opening 2a (see FIG. 2G), and formation of the recess 1a-1 by blasting from one side ( 2 (h)), through hole 1a-2 is formed by blasting from the other side (see FIG. 2 (i)), and the second resist mask 3 is peeled off (see FIG. 2 (j)). . Thereby, the printed circuit board material 1 in which the through-hole 1-1 of the predetermined diameter including the through-hole of the minimum diameter which penetrates the insulating base material 1a and the copper images 1a on both sides is formed is obtained.
Furthermore, as in the first embodiment, a printed circuit board is completed by forming a wiring pattern.

According to the printed circuit board manufacturing method of the present embodiment, the first resist mask 2 used in forming the opening 1b-1 of the copper layer 1b by etching is further used as a blasting mask. The recesses 1a-1 ′ and 1a-2 ′ are formed by blasting the insulating base material 1a in the portion exposed from the opening 2a and the opening 1b-1 of the copper layer 1b. Of the second resist mask 3 and the portion of the second resist mask 3 exposed from the second opening 3a of the portion to be removed in blasting using the copper layer 1b as a blasting mask The thickness of 1a can be reduced. As a result, the second resist layer 3 ′ used for forming the second resist mask 3 can be thin, and the cost can be reduced accordingly. Further, the fine abrasive grains can reduce the amount of collision at the time of blasting to the portion around the opening 1b-1 in the copper layer 1b slightly exposed from the second opening 3a of the second resist mask 3. The through hole 1-1 with higher accuracy can be formed.
Other functions and effects are substantially the same as those of the first embodiment.

Example 1
In this example, a printed circuit board including a through hole with a minimum diameter having a minimum diameter of, for example, φ30 μm was manufactured.
First, as the printed circuit board material 1, a multilayer copper clad laminate having a 10 μm thick copper layer 1b on both sides of a 60 μm thick insulating substrate 1a was prepared (see FIG. 1 (a)).
Next, a first dry film resist 2 ′ having a thickness of 15 μm is laminated on both surfaces of the printed circuit board material 1 (see FIG. 1 (b)), and exposure and development are performed to form portions where through holes are to be formed. A first resist mask 2 having a first opening 2a was formed (see FIG. 1C).
Next, the printed circuit board material 1 on which the first resist mask 2 is formed is etched to dissolve and remove the copper layer 1b in the portion exposed from the first opening 2a of the first resist mask 2 for insulation. The base material 1a was exposed (refer FIG.1 (d)).
Next, the first resist mask 2 was peeled off (see FIG. 1 (e)).
Next, a second resist layer 3 ′ having a thickness of 50 μm thicker than the first resist mask is formed on both surfaces of the printed circuit board material from which the insulating substrate 1a is partially exposed (see FIG. 1 (f)). ), The second opening 3a having a diameter 10 to 40 μm larger than the first opening 2a is formed at the position where the first opening 2a of the first resist mask 2 is formed by performing exposure and development. A second resist mask 3 was formed (see FIG. 1 (g)).
Next, the thickness of the insulating substrate 1a to be processed using the second resist mask 3 and the copper layer 1b in the portion exposed from the second opening 3a of the second resist mask 3 as a blasting mask. A blasting abrasive using a blasting abrasive grain having a predetermined abrasive grain size determined by a thickness (60 μm) and a minimum opening diameter (φ30 μm) while appropriately moving a slit nozzle at a predetermined pressure and a predetermined injection amount Blasting from one side of the printed circuit board material 1 by jetting the grains, digging the insulating base material 1a in the portion exposed from the opening 1b-1 of the copper layer 1b to a thickness of approximately half, A recess 1a-1 was formed (see FIG. 1 (h)).
Next, blasting is performed from the other side of the printed circuit board material 1 in the same manner as one side, and the insulating base material 1a is dug to penetrate the bottom surface of the recess 1a-1 (see FIG. 1 (i)). A through hole 1a-2 having a predetermined diameter including a through hole having a minimum diameter of 30 μm was formed in the insulating substrate 1a.
Next, the second resist mask 3 is peeled off (see FIG. 1 (j)), and a through hole 1 having a predetermined diameter including a through hole having a minimum diameter of 30 μm that penetrates the insulating base 1a and the copper images 1a on both sides. A printed circuit board material 1 having -1 formed thereon was obtained.
Next, through holes 1-1 formed in the printed circuit board material 1 are subjected to through-hole plating or via fill plating to form conductors and perform interlayer connection (not shown). A third dry film resist is laminated on both surfaces, and a third resist mask for forming a wiring pattern by the copper layer 1b is formed using the same formation method as the first resist mask 2, and then Then, etching is performed on the copper layer 1b exposed from the third resist mask to form a predetermined wiring pattern, and then the third resist mask is removed, the through hole is conducted, and the printed board on which the wiring is formed is formed. Completed.

Example 2
In this example, as in Example 1, the preparation of the printed circuit board material 1 (see FIG. 2A), the laminate of the first dry film resist 2 ′ (see FIG. 2B), the first resist After forming the mask 2 (see FIG. 2 (c)) and exposing the insulating base 1a (see FIG. 2 (d1)) by forming the opening 1b-1 of the copper layer 1b, the insulating base 1a is exposed. The thickness (60 μm) of the insulating substrate 1a to be processed and the first resist mask 2 used for the etching process are further used as a blasting mask within a range where the first resist mask 2 is not removed. Using blasting abrasive grains having a predetermined abrasive grain diameter determined by the minimum opening diameter (φ20 μm), blasting abrasive grains are sprayed while moving the slit nozzle as appropriate at a predetermined pressure and a predetermined injection amount. Brass from both sides of printed circuit board material 1 The insulating base material 1a in the part exposed from the 1st opening part 2a of the 1st resist mask 2 and the opening part 1b-1 of the copper layer 1b is processed by thickness about about 1/4. The recesses 1a-1 ′ and 1a-2 ′ were formed by digging (see FIG. 2 (d2)).
Thereafter, as in Example 1, the first resist mask 2 is peeled off (see FIG. 2 (e)), the second dry film resist 3 ′ is laminated (see FIG. 2 (f)), and the diameter is the first. Formation of the second resist mask 3 having a second opening 3a slightly larger than the opening 2a (see FIG. 2G), and formation of the recess 1a-1 by blasting from one side ( 2 (h)), through hole 1a-2 is formed by blasting from the other side (see FIG. 2 (i)), and the second resist mask 3 is peeled off (see FIG. 2 (j)). A printed circuit board material 1 having a through hole 1-1 having a predetermined diameter including a through hole having a minimum diameter of 30 μm that penetrates the insulating base 1a and the copper images 1a on both sides was obtained.
Further, a wiring pattern was formed in the same manner as in Example 1 to complete a printed board.

Comparative Example FIG. 3 is an explanatory diagram showing an example of a printed circuit board manufacturing process according to a comparative example.
In the comparative example, similarly to Example 1, after preparing the printed board material 1 (see FIG. 3A), a resist layer 4 ′ having a thickness of 50 m was formed on both sides of the printed board material 1 (see FIG. 3). 3 (b)).
Next, in the same manner as in Example 1, exposure and development are performed to form a resist mask 4 having an opening 4a in a portion where a through hole is to be formed (see FIG. 3C). Etching was performed on the printed circuit board material 1 on which the mask 4 was formed, and the copper layer 1b in the portion exposed from the opening 4a of the resist mask 4 was dissolved and removed to expose the insulating base material 1a (FIG. 3D). reference).
Next, the resist mask 4 used for the etching process for exposing the insulating base material 1a is further used as a blasting mask, and the thickness (60 μm) and the minimum opening diameter (φ30 μm) of the insulating base material 1a to be processed are used. The blasting abrasive grains having a predetermined abrasive grain size determined by the above are sprayed with blasting abrasive grains while appropriately moving the slit nozzle at a predetermined pressure and a predetermined injection amount. Blasting was performed from one side, and the insulating base 1a in the portion exposed from the opening 1b-1 of the copper layer 1b was dug to a thickness of approximately half to form the recess 1a-1 (FIG. 3 ( e)).
Next, blasting is performed from the other side of the printed circuit board material 1 in the same manner as one side, and the insulating base material 1a is dug to penetrate the bottom surface of the recess 1a-1 (see FIG. 3 (f)). A through hole 1a-2 having a predetermined diameter including a through hole having a minimum diameter of 30 μm was formed in the insulating substrate 1a.
Next, the resist mask 4 is peeled off (see FIG. 3G), and a through hole 1-1 having a predetermined diameter including a through hole having a minimum diameter of φ30 μm that penetrates the insulating substrate 1a and the copper images 1a on both sides is formed. The formed printed circuit board material 1 was obtained.
Further, a wiring pattern was formed in the same manner as in Example 1 to complete a printed board.

Processing accuracy measurement test of through hole with extremely small diameter Compared with the through hole with extremely small diameter having a minimum diameter of φ30 μm and φ20 μm formed on each printed circuit board material 1 by the manufacturing method of Example 1 and Example 2. A through hole with a very small diameter having a minimum design diameter of 30 μm formed in the printed circuit board material 1 by the manufacturing method of Example 1 was measured. The number of through-hole samples was 100.
As a result, for the through-holes having a minimum diameter of φ30 μm and φ20 μm formed in each printed circuit board material 1 by the manufacturing method of Example 1 and Example 2, the minimum hole diameter is 27 μm. The penetration rate was 100% at 17 μm, which was a very stable processing result.
On the other hand, for a through hole with a minimum diameter of 30 μm in design value formed in each printed circuit board material 1 by the manufacturing method of the comparative example, the minimum hole diameter was 20 μm, but the penetration rate was 90 μm. %, Stable processing was difficult.

  The method for producing a printed circuit board of the present invention is useful in a field where a substrate having a through hole with a very small diameter is required as a printed circuit board on which an electronic component corresponding to the demand for reduction in size and thickness of various electronic devices is mounted. .

DESCRIPTION OF SYMBOLS 1 Printed circuit board material 1a Insulation base material 1-1 Through-hole 1a-1, 1a-1 ', 1a-2' Recess 1a-2 Through-hole 1b Copper layer 1b-1 Opening part 2 of copper layer 1st resist mask 2a 1st opening 2 '1st resist layer (1st dry film resist)
3 Second resist mask 3a Second opening 3 'Second resist layer 4 Resist mask 4a Opening 4' Resist layer

Claims (3)

Preparing a printed circuit board material having a copper layer on both sides of an insulating substrate;
A first opening for forming a resist layer on both sides of the printed circuit board material and forming an opening with a predetermined diameter on the copper layer on both sides at a predetermined position of the printed circuit board material; Forming a first resist mask having:
Etching and removing the copper layer in the portion exposed from the first opening of the first resist mask by etching, exposing the insulating base;
Removing the first resist mask;
A second opening having a diameter slightly larger than the first opening at a position where a resist layer is formed on both surfaces of the printed circuit board material and the first opening of the first resist mask is formed. Forming a second resist mask having:
The second resist mask and the copper layer in the portion exposed from the second opening of the second resist mask are used as a blasting mask, and are exposed from the opening of the copper layer. Forming a through hole by blasting the insulating base material at a site; and
Removing the second resist mask;
A printed circuit board manufacturing method comprising:   2. The printed circuit board according to claim 1, wherein a resist layer used for forming the second resist mask is thicker than a resist layer used for forming the first resist mask. 3. Production method.   Between the step of exposing the insulating base and the step of removing the first resist mask, the first resist mask used for the etching processing for exposing the insulating base is further used as a blast processing mask. And a step of forming a recess by blasting the insulating substrate in a portion exposed from the first opening of the first resist mask and the opening of the copper layer. The manufacturing method of the printed circuit board of Claim 1.

Images