JPH11251746A - Manufacture of thin-type multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the space of each via hole in the most outer layer and thereby increase the density of via holes by using through hole lands of a shield board as pads for connecting the via holes which are formed on the surfaces of the most outer layers have a circular shape concentrical with a through hole and have a taper angle. SOLUTION: This shield board of two or more layers has through hole lands 14, 15, 16, 17, a conduction connection hole 12, inner layer conductors 4, 5, hole filling insulating resin 9 and the like. On the front and the rear face of the shield board, an epoxy resin-made interlayer adhesive 19A, 19B is applied for multilayer bonding. The through hole lands 14, 15, 16, 17 are used as pads for connecting via holes 31, 32 on the surfaces of the most outer layers, and via holes 31, 32 having a taper angle of 9-19 deg. and a circular shape concentrical with the conduction connection hole 12 are formed. By this method, a thin-type multilayer printed wiring board which is suitable for reduction in thickness and high-density mounting and has an excellent connection reliability can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board having two or more layers, and more particularly to a thin multilayer printed wiring board having a taper angle by using a through hole land of an inner shield plate as a connection pad for forming a via hole in an outermost layer. It relates to a manufacturing method.

[0002]

2. Description of the Related Art With the rapid spread of multimedia terminals and multifunctional, high-precision information communication devices which can be regarded as typical of light, thin, small and high-performance devices in recent years, printed wiring boards for mounting electronic components used in these devices have been developed. The demand for high-density packaging and thinning is accelerating. Also, as a method of manufacturing a printed wiring board, it is rapidly progressing to achieve high-density mounting, thinning, and cost reduction by a manufacturing method of sequentially stacking circuits by electrically connecting a large number of via holes. It is the present situation. 6 (a) to 6 (c) and FIG.
The manufacturing process will be described with reference to FIG.

First, as shown in FIG. 6A, a glass cloth epoxy copper having a thickness of about 0.8 to 1.2 mm including front and back copper foils 41 and 42, inner layer conductors 44 and 45, and an insulating substrate 43. After selectively drilling a through hole 46 in the laminated laminate 43A using a 0.4 mmφ drill, a chemical plating and an electrolytic copper plating are used together, and a first hole is formed on the inner wall of the through hole 46 and the entire front and back surfaces of the insulating substrate 43A. The copper plating layers 47 and 48 are deposited and formed.

[0006] Next, as shown in FIG. 6 (b), a hole is filled by a screen printing method using a metal mask in a hole of the conductive connection hole 52 in which first copper plating layers 47 and 48 are formed on the inner wall of the through hole 46. After applying and drying the insulating resin 49 in an arc shape, a mechanical method (brush buff)
After polishing, a through-etching method and a peeling step are performed, and throughhole lands 54, 55, 56, 57 and wiring layer 50
51 are formed.

Next, as shown in FIG. 6 (c), the front and back surfaces formed in FIG. 6 (b) are subjected to oxidation-reduction treatment, and a prepreg 58A having a single-sided copper foil and an adhesive adhered to the front and back surfaces.
-Arrange 58B and make a multilayer adhesive 59. Thereafter, using a drill or end mill having a diameter larger than the diameter of the through hole 46 of the inner layer plate, the via non-through holes 60 and 61 are drilled to a depth reaching the through hole lands 54, 55, 56 and 57 layers. Is an essential step.

[0007] Next, as shown in FIG. 7 (d), potassium permanganate treatment or the like is performed to remove carbides 46 A adhering to the inner walls of the via non-through holes 60 and 61 at the time of drilling. The second copper plating layers 47A and 48B are applied by using both chemical plating and electrolytic copper plating. Thereafter, the via holes 62 and 63 in the outermost layer are subjected to photoetching and peeling steps.
And the wiring layers 50 and 51 can be formed, and then the permanent thermosetting resists 64 and 65 are photo-coated and dried to obtain a thin multilayer printed wiring board manufacturing method 67 according to the prior art having a large occupied area. Things.

Next, as shown in FIG. 8, when the via non-through holes 60 and 61 are formed,
61 The taper angles 60A and 61A with respect to the axis of the hole in the wall are 0
In this corner portion, a turning defect portion 66 with second copper plating 47A / 48B occurs at this corner portion,
FIG. 4 is a schematic cross-sectional view of a main part according to a related art, in which a crack phenomenon may occur in a reflow process and electrical connection reliability is lacking.

[0008]

However, in the above-described method 67 for manufacturing a thin multilayer printed wiring board according to the prior art, first, the via non-through holes 60 and 6 are first used.
One diameter (φ) is larger than the diameter of the through hole 46 (φ) (φ)
Because of the essential processing conditions, it may be difficult to reduce the space and increase the density of the outermost via holes 62 and 63.

Further, by using an end mill drill for drilling the via non-through holes 60 and 61, the through hole land 5 is formed.
It is necessary to make the thickness of 4.55.56.57 as thick as about 50 to 60 μm, and there is a possibility that it is difficult to reduce the thickness and cost.

Next, as the second, a via non-through hole 6 is formed.
Since the end mill and the drill are used for drilling of 0.61 and 0.61, the taper angle 6 with respect to the axis of the hole of the wall of the non-via hole 60 and 61 is used.
Since 0A and 61A are drilled at 0 degrees, poor cornering portions 66 of the second copper platings 47A and 48B occur at these corners, causing a problem in electrical connection reliability under a reflow environment. There is fear.

Accordingly, the present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to solve the above-described problems and to provide a more excellent method 35 of manufacturing a thin multilayer printed wiring board. Is to do.

[0012]

According to the present invention, wiring layers 10 and 11 and conductive connection holes 1 are formed by two or more shield plates 18.
2 and throughhole lands 14, 15, 16 and 17, and an interlayer adhesive 19 A
19B is formed as a multilayer adhesive 20A / 20B, and the outermost via hole 31 electrically connected to the shield plate 18 is formed.
32. A method for manufacturing a thin multilayer printed wiring board formed by forming the through holes 32, 15.16, 17 of the shield plate 18 on the front and back surfaces of the outermost layer on the same axis as the through holes 12. 27.2 taper angle with core circle shape
This is intended to provide a manufacturing process used for connecting pads of the via holes 31 and 32 having 8.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A shield plate 1 having two or more layers according to the present invention.
At 8, Surholeland 14, 15, 16, 17,
It has a conductive connection hole 12, inner layer conductors 4 and 5, filling insulating resin 9, etc., and an interlayer adhesive 19 made of epoxy resin on the front and back.
A, 19B are provided, and multi-layer adhesives 20A, 20B are formed, and the through hole lands 14, 15, 16, 17 layers are used as connection pads for forming via holes 31, 32 on the front and back surfaces of the outermost layer. The via holes 31 and 32 have a taper angle of 9 to 19 degrees and are formed in concentric circular shapes on the same axis of the conductive connection holes 12 so as to reduce the thickness, increase the mounting density, increase the electrical density, It is intended to realize a method 35 for producing a thin multilayer printed wiring board having excellent connection reliability.

[0014]

2 (a) to 2 (b), 3 (c) to 3 (d), 4 (e) and 4 (e) show the manufacturing steps of an embodiment of the present invention.
This will be specifically described with reference to FIGS.

(Embodiment 1) First, as shown in FIG. 2A, front and back copper foils 1.2, thickness 18 μm, inner layer conductors 44.4
5, a glass epoxy copper clad laminate (thickness 0.4 to 0.6 mm) consisting of an insulating substrate 3 and a thickness of 35 μm (18 μm)
Automatic numerical control drilling machine (MARK-10, manufactured by Hitachi Seiko) using micro-drill diameter 0.2mmφ selectively for FR-4)
0), the first copper plating layers 7 and 8 are formed by performing chemical plating and electrolytic copper plating together to a thickness of 20 to 25 μm on the inner wall and the entire front and back surfaces of the through hole 6 after forming the through hole 6; A conductive connection hole (through hole) 12 is obtained.

Next, as shown in FIG. 2 (b), a hole filling insulating resin 9 (epoxy modified resin or the like) is permanently filled in the conductive connection hole 12 by a screen printing method using a metal mask selectively. Drying (temperature 150-160 ° C
・ Time 40 to 50 minutes) After curing and closing, the front and back conductive connection holes 1
Permanent hole filling insulating resin 9 formed in the shape of an arc projection on 2
The upper side is polished using a mechanical method (brush buff) so as to be lower than the first copper plating layers 7.8 by less than 5 μm. Thereafter, the wiring layer 10 is subjected to a photo-etching method and a stripping process.
11 and the shield plate 18 including the throughhole lands 14, 15, 16, 17.

The through hole land 14 and the through hole land 1 serving as connection pads for the via holes 31 and 32 are provided.
6 and the distance between the throughhole land 15 and the throughhole land 17 are preferably in the range of 110 to 300 μm, more preferably in the range of 200 to 250 μm.

First, the distance between the throughhole lands 14 and 16, and between the throughhole lands 15 and 17 is 110 μm.
If it is less than 1, the through hole 6 is not suitable for mass production due to the minute hole diameter (less than 0.15 mmφ) when it is drilled, and if it exceeds 300 μm, the through hole land 14. The spacing between 15, 16, and 17 becomes large, which is not suitable for reducing the space and increasing the density.

Second, the through hole land 1
The thickness of 4.15.16.17 is preferably in the range of 30 to 60 μm, more preferably in the range of 40 to 50 μm.

In addition, the above-mentioned throughhole lands 14, 15,.
When the thickness of 16.17 is less than 30 μm, when performing transverse excitation type atmospheric pressure type CO ₂ laser processing, dent deformation and voids occur due to the thickness of the thin land, which is not suitable. If it exceeds 60 μm, it is suitable for laser processing but not suitable for thinning, and neither is suitable.

Next, as shown in FIG. 3 (c), firstly, the entire surface of the shield plate 18 containing the insulating resin 9 filled with holes is chemically hydrophilicized and roughened (for example, alkalinized manganate). In the case of performing an anchor effect by using a solution, the surface roughness Ra on the throughhole lands 14, 15, 16, 17 is preferably in the range of 3 to 30 μm, more preferably 10 to 15 μm. .

Further, the above-mentioned throughhole lands 14.15.
If the surface roughness Ra on the surfaces 16 and 17 is less than 3 μm, the diameters of the bottom surfaces of the via holes 31 and 32 are too smooth, and the adhesion strength of the second copper plating layers 7A and 8B may be insufficient. When the thickness exceeds 30 μm, the second copper plating layers 7A and 8B are deposited to a thickness of about 3 to 5 μm thinly on the bubbling portion, which may cause poor electrical connectivity due to the solder reflow process. Absent.

The permanganate is preferably an oxidizing agent such as sodium permanganate or potassium permanganate, and sodium hydroxide, potassium hydroxide, potassium carbonate or sodium carbonate as an alkaline agent. Frequently, one or more of the above permanganates and alkali agents are arbitrarily combined and mixed for use. The liquid temperature may be, for example, about 45 to 65 ° C., and the immersion time may be, for example, 3
It takes about 15 minutes.

Next, after the interlayer adhesives 19A and 19B made of an epoxy adhesive film (Hitachi Chemical Co., Ltd., AS3000) having a thickness of about 50 μm are provided on the front and back surfaces of the shield plate 18, they are formed by the multilayer adhesives 20A and 20B. Then, when the via holes 31 and 32 are formed concentrically on the same axis as the conductive connection holes 12 of the shield plate 18 and a masking method is used to process the transversely excited atmospheric pressure type CO ₂ laser, The taper angle 27/28 with respect to the axis of the hole of the via non-through hole 21/23 is preferably in the range of 9 to 19 degrees, more preferably 13 to 16 degrees.

When the taper angles 27 and 28 are less than 9 degrees, the taper angles 27 and 28 with respect to the axis of the hole on the wall surface of the non-via holes 21 and 23 become acute angles (approaching 0 degrees). Since drilling is performed, there is a possibility that a turning failure portion 66 with copper plating may occur at the bottom corner portion, and there is a problem in electrical connection reliability. If it exceeds 19 degrees, the via non-through hole 21 -The upper diameter of 23 is large, so that it is difficult to realize high-density mounting without reducing the space, and neither is suitable.

Next, when the via non-through holes 21 and 23 are formed by the lateral excitation type atmospheric pressure type CO ₂ laser processing method, the through hole lands 14, 15, 16.
Carbide 24 adheres as a residue to the surface 17 and the insulating resin 9 to fill the hole with a thickness of less than about 1 μm. In order to remove the carbides 24, for example, an alkaline potassium permanganate solution, C
The temperature is preferably about 1 to 2 minutes at a liquid temperature of 40 to 50 ° C. using an rO ₃ -alkali solution or the like.

Next, as shown in FIG. 3 (d), on the front and back of the outermost layer, a photosensitive film (resist) of Photek, negative type (trade name, manufactured by Hitachi Chemical Co., Ltd., aqueous developing type SR-30)
00), and after forming the permanent resist layers 29 and 30,
Electroless copper plating (manufactured by Hitachi AIC) is applied at about 5 μm / Hr for about 20 hours to form a via hole 31 having a taper angle.
Form 32.

Next, as shown in FIG. 4E, a solder mask 3 is formed by screen printing using a metal mask as the outermost layer.
After applying a thickness of about 3.3 μm and a thickness of about 70 μm, a fusing step at a temperature of 340 ° C. for a time of about 0.5 minute is performed to obtain a method 35 for manufacturing a thin multilayer printed wiring board of the present invention, which realizes high-density mounting and thinning. .

As shown in FIG. 1, the shield plate 18
Are used as connection pads, via non-through holes 21 and 23 having a taper angle of about 9 to 19 degrees are formed, and via holes 31 and 32 having an upper diameter of about 100 μm are formed. 4-5% than before
It is a schematic cross section which shows the Example of the manufacturing method 35 of the thin multi-layer printed wiring board of this invention which was able to achieve small space, high-density mounting, and thinning.

Next, as shown in FIG. 5, when the non-via holes 21 and 23 are provided by the CO ₂ laser processing, the via holes 12 and 23 are formed in a concentric circle shape substantially coaxial with the through hole 12 of the shield plate 18. FIG. 9 is a schematic cross-sectional view of a main part in which taper angles 27 and 28 with respect to the axis of the hole of the wall surfaces of the via non-through holes 21 and 23 are formed in the range of 9 to 19 degrees.

Next, the via holes 31.
Table 1 shows test results of connection reliability by thermal shock (MIL-107) of 32 connection parts. From the above results, when the through-hole lands 14, 15, 16, 17 are used as the connection pads, the taper angle with respect to the axis of the hole of the wall of the via non-through holes 21, 23 is about 13 to 16 degrees. Optimum conditions could be obtained (35). Margin below.

[0032]

[Table 1] (1) Connection reliability (hot oil) Cycle 5 from 260 ° C, 5 seconds (oil) → 20 ° C (water) 5 (2) JIS, passed 10 cycles or more. (3) Sample via hole (hole): 100 hole pattern. (4) Via hole upper diameter 100 μm (lateral excitation type atmospheric pressure type C
O ₂ laser processing) (5) prior art ... end mills, drill

[0033]

(1) According to the method 35 for manufacturing a thin multilayer printed wiring board of the present invention, the through-hole lands 14, 15, 16 and 17 of the shield plate 18 are connected to the via holes 3 of the outermost layer.
Used for connection pads for forming 1.32, taper angle 27.2
The formation of the micro via holes 31 and 32 having the thickness 8 eliminates the copper plating thickness at the corners, improves the reliability, reduces the area occupied by the through holes by 4 to 5%, increases the mounting density, and shortens the wiring length. It is feasible to increase the speed of signal transmission, and the effect of contributing to industry is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIGS. 2A and 2B are cross-sectional views showing an embodiment of the present invention.

3 (c) to 3 (d) are cross-sectional views showing an embodiment of the present invention.

FIG. 4E is a sectional view showing an embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a main part, illustrating the processing of holes 21 and 23 by the laser of the present invention.

FIGS. 6A to 6C are cross-sectional views showing a conventional manufacturing method.

FIG. 7D is a cross-sectional view showing a conventional manufacturing method.

FIG. 8 is a schematic cross-sectional view of a main part illustrating a defective portion 66 with copper plating around corners of via holes 62 and 63 according to a conventional technique.

[Explanation of symbols]

1.2 Copper foil 3 Insulating substrate 4.5 Inner layer conductor 6
Through hole 7.8 First copper plating layer 7A / 8B Second copper plating layer 9 Filling insulating resin 10.11 Wiring layer 12 Conductive connection hole (through hole) 13 Surface roughness Ra on through hole 14. 15.16.17 ... Surhole land 18 ... Shield plate (glass cloth epoxy copper clad laminate with inner layer circuit) 19A / 19B ... Interlayer adhesive 20A / 20B ... Multilayer bonding 21.23 ... Via non-through hole 24 ... Carbide 27・ 28
... Taper angle (.theta.) 29/30 Permanent photosensitive resist 31/32 Via hole 33/34 Solder 35 ... Method of manufacturing thin multilayer printed wiring board of the present invention 41/42 Copper foil 43 ... Insulating substrate 43A ... Glass cloth Epoxy copper-clad laminates 44/45 ... Inner layer conductor 46 ... Through hole 46A ... Carbide 47/48 ... First copper plating layer 47A / 48B ... Second copper plating layer 49 ... Filling insulating resin 50/51 ... Wiring layer 52 ... Conduction Connection hole (Sur hole) 54, 55, 56, 57: Sur hole land 58A, 58B: Single-sided copper foil, prepreg with adhesive 5
9 Multi-layer bonding 60 ・ 61 ・ ・ ・ Via non-through hole 60A ・ 61A ・ ・ ・ Taper angle (θ) 62 ・ 63 ・ ・ ・ Via hole 64 ・ 65 ・ ・ ・ Heat-hardening resist 66 ・ ・ ・ Poor turning defect with copper plating 67 ・ ・ ・ Conventional technology Method for manufacturing such a thin multilayer printed wiring board

Claims (3)

[Claims] In a shield plate (18) having two or more inner layers, wiring layers (10) and (11) and conductive connection holes (1) are provided.
2) and Sur Hall Land (14) ・ (15) ・ (1)
6) and (17), wherein the inner shield plate (1)
8) Interlayer adhesives (19A) and (19B) are formed on the front and back surfaces by multi-layer bonding (20A) and (20B), and the outermost via holes (31) are electrically connected to the shield plate (18). A method of manufacturing a thin multilayer printed wiring board formed by forming (32) by CO ₂ laser processing, wherein the through hole land (1) of the inner layer shield plate (18) is provided;
4) A via hole (31) in which (15), (16), and (17) are formed on the front and back surfaces of the outermost layer in a concentric circular shape on the same axis as the through hole (12) and provided with taper angles (27) and (28). )
-The method (35) for manufacturing a thin multilayer printed wiring board according to the present invention, wherein the method is used for the connection pad of (32), and high-density mounting and high-speed operation can be performed. 2. The distance between the front through hole land (14) and the front through hole land (16) used for the connection pads for the via holes (31) and (32) formed in the outermost layer and the back through hole land according to claim 1. The distance between (15) and the back throughhole land (17) is 110 μm to 30 μm.
A via hole (31) having a diameter of 0 μm or a concentric circle on the same axis as the through hole (12) of the shield plate (18).
· Forming (32) to form non-via holes (21) and (23)
The taper angles (27) and (28) with respect to the axis of the hole in the wall surface are 9
A method for manufacturing a thin multilayer printed wiring board (35), wherein the thin-film multilayer printed wiring board is formed at a temperature in the range of about to 19 degrees. 3. The connection pad according to claim 1, wherein the surface roughness Ra (13) on the throughhole lands (14), (15), (16) and (17) is in a range of 3 to 30 μm or the connection pad. Surholeland used (14) ・ (15)
(16) A method for producing a thin multilayer printed wiring board (35), wherein the thickness of (16) or (17) is formed in the range of 30 to 60 μm.