JPH08264951A - Multilayer printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE: To easily fill a plated through-hole in an additive adhesive layer with paste by a method wherein a photo viahole larger than the plated through- hole is made to serve as the one of two openings of the through-holes. CONSTITUTION: A multilayer printed wiring board 1 is equipped with an inner board 2 where an inner conductor circuit is provided, additive adhesive layers 5 and 6 formed on the inner board 2, and a plated through-hole 13 through the inner board 2. A photo viahole 15 larger in diameter than the plated through-hole 13 is made in the additive adhesive agent layers 5 and 6 at prescribed spots and made to serve as an opening 13a of the through-hole 13. By this setup, as the opening 13a of the through-hole 13 is larger in diameter, paste is easily fed into the plated though-hole 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as a manufacturing technique of a multilayer printed wiring board, a full additive process for forming a conductor circuit by only electroless plating is known. Here, the flow of a general full additive process will be briefly described with reference to FIG.

First, an inner layer substrate 22 having an inner layer conductor circuit 21 is produced, and then an additive adhesive layer 23 is formed by applying and curing a resin varnish. Next, a recess for forming a photo via hole is formed in the additive adhesive layer 23 by photolithography. Next, after roughening the additive adhesive layer 23, a through hole forming hole is transparently formed by using a drill or the like (drilling step). Next, after performing desmearing treatment and providing catalyst nuclei, a plating resist 24 is formed on the additive adhesive layer 23. Next, electroless copper plating is performed to deposit the copper plating 25 on the inner wall surface of the recess for forming the photo via hole, the inner wall surface of the hole for forming the through hole, and the like. After that, an inspection step is performed to obtain a multilayer printed wiring board 28 including the outer layer conductor circuit 26, the plated through holes 27, and the photo via holes (not shown).

[0004]

By the way, in the full additive process, when a surface polishing step by a polishing machine is carried out after the electroless plating step in order to remove the copper plating 25 and the like abnormally deposited on the plating resist 24. There is.

However, as shown in FIG. 9, when the above-described drilling process is carried out, the cutting chips of the drill, which come out from the upper opening of the through-hole forming hole, are scattered and welded to the periphery thereof, Raised part 3 on the part
There was a problem that 0 was possible. This is also because, in the case of a full-additive substrate, unlike the subtractive substrate using a copper clad laminate as a starting material, heat generated during cutting is difficult to dissipate from the surface. Therefore, when the surface polishing step is performed, the copper plating 25 on the upper surface of the raised portion 30 is scraped off, which often causes disconnection. Therefore, in the past, it was necessary to remove cuttings using a soft brush or the like. However, this method cannot completely remove the cutting waste, and the work itself is troublesome.

Further, as another failure mode due to the drilling process, it is known that, as shown in FIG. 10, a chip 31 or a crack 32 is generated at the opening of the through hole forming hole by the impact of a drill or the like. It was being done. For this reason, not only does the appearance of the plated through hole 27 deteriorate, but also the reliability of the plated through hole 27 is likely to deteriorate.

The present invention has been made to solve the above problems, and an object thereof is to prevent a disconnection in a plated through hole portion and to improve reliability, and a manufacturing method thereof. To provide.

[0008]

In order to solve the above problems, according to the invention of claim 1, an inner layer substrate on which an inner layer conductor circuit is formed, and an additive adhesive layer formed on the inner layer substrate. And a multilayer printed wiring board having a plated through hole penetrating the inner layer substrate, a photo via hole having a diameter larger than that of the plated through hole is provided at a predetermined position of the additive adhesive layer, and the photo via hole is formed. The gist is a multilayer printed wiring board having one opening in the plated through hole.

According to a second aspect of the invention, in the first aspect, a part of the inner layer conductor circuit is routed to the bottom of the photovia hole, and the upper surface of the routed inner layer conductor circuit and The two side surfaces are assumed to be joined to the plating in the photo via hole.

According to a third aspect of the present invention, a step of forming an additive adhesive layer made of a photosensitive resin on both the front and back surfaces of the inner layer substrate on which the inner layer conductor circuit is formed, and a photo process at a predetermined position of the additive adhesive layer. A step of forming a recess for forming a photo via hole by lithography, and a step of forming a through hole forming hole that opens at the bottom of the recess by punching the inner layer substrate from the surface side where the recess is formed; The gist is a method for manufacturing a multilayer printed wiring board, which comprises a step of depositing plating in the through-hole forming holes.

[0011]

According to the third aspect of the present invention, since the tip of the drilling tool does not directly contact the additive adhesive layer during the drilling process, the amount of cutting chips that cause swelling is extremely small. Become. Further, since the additive adhesive layer is less likely to be impacted, cracks and cracks are less likely to occur around the openings of the through-hole forming holes.

According to the first and second aspects of the present invention, since the opening on one side of the plated through hole has a large diameter, it is easy to fill the paste into the plated through hole. According to the second aspect of the present invention, the joint area between the conductors is increased, so that the connection reliability inside the plated through hole is improved.

[0013]

【Example】

[Embodiment 1] Hereinafter, an embodiment in which the present invention is embodied in a method for manufacturing a multilayer printed wiring board by an additive process will be described in detail with reference to FIGS.

FIG. 7 shows a multilayer printed wiring board 1 according to this embodiment. This multilayer printed wiring board 1
Is a so-called four-layer plate having four conductor layers. Inner layer conductor circuits 3 and 4 are formed on both the front surface S1 and the back surface S2 of the inner layer substrate 2 that constitutes the multilayer printed wiring board 1. Additive adhesive layers 5 and 6 having a thickness of several tens of μm are formed on both front and back surfaces of the inner layer substrate 2 so as to cover the inner layer conductor circuits 3 and 4. On the upper surfaces of these additive adhesive layers 5 and 6, a permanent resist 7 as a plating resist and outer layer conductor circuits 8 and 9 are formed. Interstitial via holes 10 as photo via holes are formed in the additive adhesive layers 5 and 6 on the front surface S1 and the back surface S2. The interstitial via hole 10 is formed by copper plating 12 on the inner wall surface of the recess 11 for forming the photo via hole.
Is formed by precipitating. The interstitial via hole 10 on the front surface S1 side electrically connects the inner layer conductor circuit 3 and the outer layer conductor circuit 8 existing outside thereof. Similarly, the interstitial via hole 10 on the back surface S2 side electrically connects the inner layer conductor circuit 4 and the outer layer conductor circuit 9 existing outside thereof.

Further, this multilayer printed wiring board 1 has plated through holes (in this embodiment, inner diameter D2 = about 0.3 m).
m) 13 is provided. Plated through hole 13
Is copper plated 12 on the inner wall surface of the through hole forming hole 14.
Is formed by precipitating. The plated through holes 13 are formed by the outer conductor circuit 8 on the front surface S1 side and the back surface S1.
The outer layer conductor circuit 9 on the second side is electrically connected.

Another interstitial via hole 15 having a different role from that of the above-mentioned interstitial via hole 10 is formed at a predetermined position in the additive adhesive layer 5 on the surface S1 side. The interstitial via hole 15 is formed by depositing the copper plating 12 on the inner wall surface of the recess 16 for forming the photo via hole. The plated through hole 13 is
It is provided coaxially so as to pass through the bottom of the interstitial via hole 15. Therefore, the interstitial via hole 15 serves as the front surface side opening 13 a of the plated through hole 13.

The inner diameter D1 of the interstitial via hole 15 is set to be equal to or larger than the inner diameter D2 of the plated through hole 13, more preferably about 0.1 mm to about 0.2 mm larger than the inner diameter D2. It The range that the inner diameter D1 can take, of course, changes according to the value of the inner diameter D2. If the value of the inner diameter D1 is too small, the additive adhesive layer 5 is likely to be impacted during drilling, and it may not be possible to sufficiently prevent cracks and cracks.
On the other hand, if the inner diameter D1 is too large, problems such as chipping and cracks will not occur, but there is a risk of hindering fineness. In consideration of such circumstances, in the case of this embodiment in which the inner diameter D2 is set to about 0.3 mm, the inner diameter D1 is set to about 0.
It is set to 5 mm.

On the other hand, in the case of this multilayer printed wiring board 1,
The above-mentioned interstitial via hole 15 is not provided at all in the additive adhesive layer 6 on the back surface S2 side. That is, in the multilayer printed wiring board 1 of this embodiment, it can be understood that only one end of the plated through hole 13 (that is, only the end on the surface S1 side) has a large diameter. Hereinafter, the interstitial via hole 10 mentioned above will be referred to as "first IVH 10",
The interstitial via hole 15 to be described later is referred to as "second
They are distinguished by calling them IVH15 ”.

Next, the procedure for manufacturing the multilayer printed wiring board 1 will be described with reference to FIGS. First, a copper clad laminate (FR-4 in this embodiment, thickness 0.6 mm) is used as a starting material, and copper foil is etched according to a normal subtractive process. As a result, the inner layer conductor circuits 3, 4
The inner layer substrate 2 having the above is manufactured.

Next, a resin varnish for forming an additive adhesive layer is applied to the front surface S1 and the back surface S2 of the inner layer substrate 2 by a coating device such as a roll coater. The resin varnish is a photosensitive resin matrix that is poorly soluble in a roughening agent such as chromic acid, in which a resin filler that is easily soluble in the roughening agent is dispersed. Further, the applied resin varnish is cured by heating and drying the inner layer substrate 2. As a result, as shown in FIG. 2, the additive adhesive layers 5 and 6 having a thickness of 40 μm to 80 μm are formed on the inner layer substrate 2. In this embodiment, the adhesive varnishes 5 and 6 having a thickness of 50 μm are formed by applying and curing a resin varnish made of a photosensitive epoxy acrylate and a thermosetting epoxy.

Next, by performing exposure and development using a photomask, the first portions are formed on the predetermined portions of the additive adhesive layers 5 and 6, that is, the portions corresponding to the inner layer conductor circuits 3 and 4 which require conduction. Recess 1 for forming IVH 10
1 (see FIG. 3). In this process, the surface S
A circular recess 16 for forming the second IVH 15 is formed at a predetermined portion of the additive adhesive layer 5 on the first side, that is, a portion P1 where a plated through hole is to be formed. The inner diameter of the recess 16 in this embodiment (specifically, the inner diameter of the bottom portion) D
1 is 0.5 mm. Here, the recess 16 is formed by an optical method such as photolithography. Therefore, unlike the case of a mechanical method using the drill 17 or the like, problems such as scattering and welding of cutting waste do not occur.

Next, as shown in FIG. 4, the inner layer substrate 2 in which the recesses 16 are formed is treated with a roughening agent such as chromic acid to select the resin filler in the additive adhesive layers 5 and 6. To dissolve it. As a result of such a roughening treatment, the roughened surface 5a,
6a is formed.

Next, using a drilling tool such as a drill 17 or the like, the planned plating through hole formation portion P1 of the inner layer substrate 2 which has been subjected to the roughening treatment is replaced with the surface S1 on which the concave portion 16 is formed.
Perforate only from the side (see Figure 5). In this case, drill 1
The central axis of 7 is aligned so as to penetrate substantially the center point of the recess 16. Then, as a result of the drilling step, as shown in FIG. 6, a through hole forming hole 14 penetrating the front surface S1 and the back surface S2 of the inner layer substrate 2 is transparently provided. The upper end of the through-hole forming hole 14 is open at the bottom of the recess 16. In this embodiment, a drill 17 having a blade diameter of 0.3 mm is used. Further, when performing the drilling step, the inner layer substrate 2 is fixed to a jig (not shown) such that the back surface S2 is in close contact.

Next, after performing desmear treatment and catalyst nucleation according to a conventionally known procedure, as shown in FIG.
A permanent resist 7 is formed on a predetermined region on the additive adhesive layers 5 and 6 by photolithography.

Then, electroless copper plating is performed using a conventionally known electroless copper plating bath to obtain a permanent resist 7
A copper plating 12 having a thickness of about 20 μm is deposited on other portions. Further, the surface is polished by a wet belt sander (# 600) to remove the copper plating 12 which is abnormally deposited on the surface layer. After this, if the inspection process is performed, the outer conductor circuit 8,
1, the plated through hole 13, the first and second IVH holes 10, 15 and the like, and the multilayer printed wiring board 1 of FIG.
Is obtained.

The method of manufacturing the multilayer printed wiring board 1 of the present embodiment is characterized in that the recess 16 is formed by photolithography in advance at the planned plated through-hole forming portion P1 before the drilling step. Further, the recess 16 formed in this case is larger than the diameter of the drill 17. Therefore, the tip of the rotating drill 17 does not come into direct contact with the additive adhesive layer 5, but comes into contact with the inner layer substrate 2 located therebelow. Therefore, the additive adhesive layer 5 is not scraped off by the drill 17, and the amount of cutting chips that cause swelling is extremely small.
Therefore, it is possible to reliably prevent the occurrence of disconnection when the surface polishing step is performed. Further, since the troublesome work of removing the cutting waste using a soft brush or the like is not necessary, the simplification of the entire process is achieved.

Furthermore, according to the manufacturing method of this embodiment, the tip of the drill 17 does not directly contact the additive adhesive layer 5, so that the impact applied to the additive adhesive layer 5 during the drilling process is extremely small. Therefore, chipping or cracking is less likely to occur around the opening of the through hole forming hole 14. Therefore, it is possible to improve the appearance and reliability of the plated through hole 13.

Also, the second I which is essential in this embodiment is
The VH15 is the first I which is a normal photo via hole.
It can be formed at the same time when the VH 10 is formed. Therefore, no special equipment or process is specifically required, which is extremely advantageous for implementation.

Further, according to the manufacturing method of this embodiment,
Second which constitutes one opening of the plated through hole 13
IVH15 has an additive adhesive layer 5 on both sides.
There is a feature that it is formed on only one of the six (that is, only the additive adhesive layer 5 on the surface S1 side).
In addition, the second adhesive layer 5 on the surface S1 side has a second I
It is of course possible to mix the plated through hole 13 having VH15 and the plated through hole 13 having the second IVH15 in the additive adhesive layer 6 on the back surface S2 side in a single multilayer printed wiring board ( (Not shown). However, when manufacturing such a multilayer printed wiring board, it is necessary to perforate the inner layer substrate 2 from two directions in the perforation step, and therefore the inner layer substrate 2 needs to be turned over. Considering the above, the structure of the present embodiment requires less labor and time for the drilling process, and is more convenient for facilitating the manufacturing.

Then, the multilayer printed wiring board 1 of this embodiment
In this case, since the second IVH 15 is provided, the surface side opening 13a of the plated through hole 13 has a large diameter. Such a configuration is advantageous when, for example, the inner space of the plated through hole 13 is desired to be filled with a conductive paste or the like. That is, if the paste is filled from the side of the second IVH 15 having a large diameter, the paste can be relatively smoothly and surely introduced into the internal space. Therefore, the paste filling work is facilitated.

When the surface mount component is soldered to the surface side opening 13a without being filled with the paste, the solder may get caught in the recessed second IVH 15 to some extent, resulting in a strong joint strength. There is an advantage of improving. [Embodiment 2] Next, the multilayer printed wiring board 19 of Embodiment 2 will be described.
Also, the manufacturing method thereof will be described with reference to FIG. Here, the difference from the first embodiment will be mainly described, and common parts will be denoted by the same member numbers.

As shown in FIG. 8, in this multilayer printed wiring board 19, a part of the inner layer conductor circuit 3 on the front surface S1 side is routed to the bottom of the second IVH 15. Then, the upper surface 3a and the side surface 3b of the routed inner layer conductor circuit 3 are in a state of being joined to the copper plating 12 deposited in the second IVH 15 (that is, a two-point connection state). Therefore, in the case of this multilayer printed wiring board 19,
Electrical connection between the inner layer conductor circuit 3 and the plated through hole 13 is achieved.

When manufacturing the multilayer printed wiring board 19, it is necessary to first manufacture the inner layer substrate 2 according to the first embodiment. At that time, the inner layer conductor circuit 3 is also routed to the portion P1 where the through hole is to be formed. In this embodiment, the inner-layer conductor circuit 3 has a circular pattern and has a diameter at least larger than the inner diameter D2 of the through-hole forming hole 13. Further, the center of the circular inner layer conductor circuit 3 is formed in the recess 1 for forming the second IVH 15 which will be formed later.
It is almost in line with the center of 6. Then, according to Example 1, the steps from the formation of the additive adhesive layers 5 and 6 to the roughening step are performed. Next, using the drill 17 or the like, the plating through-hole forming planned portion P1 of the inner layer substrate 2 which has been subjected to the roughening treatment is perforated from only the surface S1 side. After the drilling step, the through hole forming holes 14 penetrating the front surface S1 and the back surface S2 of the inner layer substrate 2 are formed. At this time, the routed inner layer conductor circuit 3 is punched into a donut shape by the drill 17.

Then, according to the first embodiment, the steps of desmearing, providing catalyst nuclei, forming the permanent resist 7 and electroless copper plating are performed again. As a result, the copper plating 12 having a thickness of about 20 μm is deposited on the through-hole forming hole 14 and the inner wall surface of the recess 16. At this time, the copper plating 12 is
Not only the resin surface described above but also the upper surface 3a and the side surface 3b of the inner layer conductor circuit 3 exposed in the recess 16 are similarly deposited. After that, the outer layer conductor circuits 8 and 9 and the plated through holes 13 are subjected to a surface polishing step and an inspection step.
And the multilayer printed wiring board 19 of FIG. 8 including the first and second IVH holes 10 and 15 is obtained.

Needless to say, the manufacturing method of the multilayer printed wiring board 19 of the second embodiment as described above has the same effects as the first embodiment. Especially this multilayer printed wiring board 1
In No. 9, the copper plating 12 is deposited not only on the side surface 3b of the inner layer conductor circuit 3 routed to the recess 16 but also on the upper surface 3a thereof. Therefore, the joint area between the conductors is secured by the area of the upper surface 3a of the inner layer conductor circuit 3, and as a result, the connection reliability inside the plated through hole 13 is also surely improved. Therefore, it is possible to obtain the electrically more excellent multilayer printed wiring board 19.

Further, according to the structure of the present embodiment, it is possible to secure a suitable connection between the conductors in the inner layer, so that it is not necessary to perform a three-point connection state by performing etch back unlike the prior art. That is, the processing conditions can be relaxed as compared with the conventional case where the desmear processing needs to be performed under strong conditions. This surely contributes to the reduction of manufacturing time and cost.

The present invention can be modified as follows, for example. (1) The inner layer conductor circuit 3 routed in Example 2 is
It does not necessarily have to be a circular pattern, and may have any shape such as a linear pattern. However,
The pattern having the shape as in Example 2 has an advantage that the bonding area becomes relatively large.

(2) Since the shape of the second IVH 15 does not have to be circular, it may of course be elliptical, rectangular, polygonal or the like. However, the opening area of the second IVH 15 is preferably at least larger than the opening area of the front surface side opening 13a of the plated through hole 13.

(3) The electroless plating on the portion where the permanent resist 7 is not formed is not limited to the electroless copper plating as in Examples 1 and 2, but may be electroless nickel plating or the like. Further, electroless copper plating and other plating may be used together.

(4) Instead of the method of Examples 1 and 2 in which the additive adhesive layers 5 and 6 are formed by applying and curing a resin varnish, for example, a method of laminating an additive adhesive forming sheet is adopted. Is also possible.

(5) The present invention is the same as the first and second embodiments.
It is of course possible to apply not only to the layered plate but also to a three-layered plate or a multi-layered plate of five or more layers (in this case, the adhesive adhesive layers 5 and 6 on one side include a plurality of layers).

Here, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-mentioned embodiments and other examples will be listed below together with their effects. (1) A photo via hole having a diameter larger than that of the plated through hole is provided at a predetermined position of the additive adhesive layer formed on the inner layer substrate having the inner layer conductor circuit, and the photo via hole is provided on one side of the plated through hole. It is an opening, and a part of the inner layer conductor circuit is routed to the bottom of the photovia hole, and two surfaces, that is, the upper surface and the side surface of the routed inner layer conductor circuit, are formed in the photovia hole hole. Plating through-hole structure joined with plating. With this configuration, improvement in reliability and the like can be achieved.

(2) In claim 3, the inner diameter of the recess is larger than the diameter of the punching tool used when punching the inner layer substrate (that is, the inner diameter of the through-hole forming hole to be formed). The manufacturing method of a multilayer printed wiring board. With this method, it is possible to reliably prevent swelling, chipping, and cracks in the opening.

(3) In Claims 1 to 3, the photo via hole forming one opening of the plated through hole is formed only on one of the additive adhesive layers on both sides. This facilitates manufacturing.

The technical terms used in this specification are defined as follows. "Plating through-holes: Those in which metal plating such as copper plating is deposited on the inner wall surface of the holes formed in the base material."

[0046]

As described above in detail, according to the invention described in claim 3, there is provided a method for manufacturing a multilayer printed wiring board capable of preventing disconnection in a plated through hole portion and improving reliability. You can Further, according to the invention described in claim 1, it is possible to provide a multilayer printed wiring board which is not only excellent in reliability in a plated through hole portion but also relatively easy for paste filling work and the like. Further, according to the invention described in claim 2, the reliability can be further improved.

[Brief description of drawings]

FIG. 1 is a partial schematic cross-sectional view showing a multilayer printed wiring board of Example 1.

FIG. 2 is a partial schematic cross-sectional view for similarly explaining the manufacturing procedure thereof.

FIG. 3 is a partial schematic cross-sectional view for similarly explaining the manufacturing procedure.

FIG. 4 is a partial schematic cross-sectional view for similarly explaining the manufacturing procedure thereof.

FIG. 5 is a partial schematic cross-sectional view for similarly explaining the manufacturing procedure.

FIG. 6 is a partial schematic cross-sectional view for explaining the same manufacturing procedure.

FIG. 7 is a partial schematic cross-sectional view for similarly explaining the manufacturing procedure thereof.

FIG. 8 is a partial schematic cross-sectional view showing a multilayer printed wiring board of Example 2.

FIG. 9A is a partial plan view for explaining the problems of the conventional multilayer printed wiring board, and FIG. 9B is a sectional view taken along line AA.

FIG. 10 is a partial schematic sectional view for explaining a conventional problem.

[Explanation of symbols]

1, 19 ... Multilayer printed wiring board, 2 ... Inner layer substrate, 3, 4
... Inner layer conductor circuit, 3a ... Upper surface of inner layer conductor circuit, 5, 6 ...
Additive adhesive layer, 12 ... Copper plating, 13 ... Plating through hole, 13a ... (Front side) opening, 14 ... Through hole forming hole, 15 ... Second IVH as photo via hole, 16 ... Photo via hole Recess for formation.

Claims (3)

[Claims] 1. A multilayer printed wiring board comprising an inner layer substrate on which an inner layer conductor circuit is formed, an additive adhesive layer formed on the inner layer substrate, and a plated through hole penetrating the inner layer substrate, A multilayer printed wiring board, wherein a photo via hole having a diameter larger than that of the plated through hole is provided at a predetermined position of the additive adhesive layer, and the photo via hole is one opening of the plated through hole. 2. A part of the inner layer conductor circuit is routed to the bottom of the photovia hole, and two surfaces of the routed inner layer conductor circuit, the upper surface and the side surface, are in the photovia hole hole. The multilayer printed wiring board according to claim 1, which is joined to the plating of. 3. A step of forming an additive adhesive layer made of a photosensitive resin on both front and back surfaces of an inner layer substrate on which an inner layer conductor circuit is formed, and for forming a photo via hole by photolithography at a predetermined portion of the additive adhesive layer. Forming a recessed portion, forming a through hole forming hole that opens at the bottom of the recessed portion by punching the inner layer substrate from the side where the recessed portion is formed, and the through hole forming hole. A method for manufacturing a multilayer printed wiring board, which comprises a step of depositing plating inside.