JP2003060351A - Multilayer wiring board with coaxial via hole and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a via hole structure which restrains electromagnetic radiation during signal transmission and reduces reflection and attenuation of a signal at high-frequency drive, by means of a via hole shape of a hole part for connection upper and lower metal wiring layers in a multilayer wiring board, and to provide its manufacturing method. SOLUTION: A multilayer wiring board, which is formed by laminating an insulation layer consisting of a resin insulation film and a wiring layer consisting of a conductor film alternately, has a vial hole which is constructed to be formed independently, without having to be connected to a signal wiring layer, a power supply and to ground layer coaxially on a concentric circle spaced a regular interval apart by an insulation layer, in a via hole connected to a signal transmission wiring ad its periphery, and is embedded in an insulation resin layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency wiring board, and more particularly to a high-frequency multilayer wiring capable of transmitting a high-frequency signal to a signal line formed by connecting a via and a conductor line provided on an insulating substrate with little transmission loss. The present invention relates to a substrate and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, the performance of semiconductors has dramatically improved, and the semiconductors have become faster (high frequency drive) and have more terminals. However, since the printed wiring board (motherboard) in the hard disk of a computer and the printed wiring board in a mobile terminal and a mobile phone have a limited area, the size of a wiring board (semiconductor package) on which a semiconductor is mounted is limited.

Conventional wiring boards have responded by miniaturizing the wiring in order to mount semiconductors having high speed and multiple terminals. However, the driving frequency of semiconductors advancing at an accelerating rate has reached the region of several hundred MHz to GHz level, and high-frequency signals cannot be transmitted only by miniaturization of wiring, which is a conventional technique.

For speeding up, in terms of wiring technology, a structure such as a microstrip line (a), a strip line (b), a coplanar strip line (c) as shown in FIG. A wiring technique having electric characteristics in consideration of electromagnetic radiation has been proposed. All of these are wiring for signal transmission, power supply and ground wiring (or layer)
Is a structure surrounded by. Designing dimensions such as the insulating layer thickness, the wiring thickness, and the wiring width for impedance matching is also a technique for high-frequency driving, and has attracted attention in recent years.

Electromagnetic radiation near the signal transmission wiring during high frequency driving is radiated three-dimensionally. In Fig. 1 (a), by arranging the signal transmission wiring and the ground layer via an insulating layer, the electric lines of force have a vector in the ground layer to stabilize electromagnetic radiation (electrical characteristics) during signal transmission. (Microstrip line). In FIG. 1 (b), by arranging a ground layer above and below the signal transmission wiring, the electrical characteristics due to electromagnetic radiation are improved (strip line). In FIG. 1 (c), the ground wiring is arranged on the same plane as the signal transmission wiring (coplanarization) so that the top, bottom, left, and right are grounded (coplanar strip line). This is a wiring structure that absorbs three-dimensionally radiated electromagnetic waves and suppresses noise generation in the adjacent signal transmission wiring, and has the most improved electrical characteristics in the current structure.

The via hole has a land for processing position accuracy, which is a laser processing characteristic, and a tapered shape of the via hole itself. Since the via hole is formed in such a complicated shape, the signal transmission characteristic during high frequency driving is poor. That is, signal reflection and attenuation always occur in the via hole. This is especially noticeable for high frequency signals. Therefore, various structures having improved electrical characteristics have also been proposed for a via hole structure in which upper and lower wirings sandwiching an insulating layer are electrically connected. For example, a method has been proposed in which vias provided in the vertical direction of an insulating substrate are made to be pseudo-coaxial by a plurality of ground layers arranged side by side on the insulating substrate around the via. In addition, the applicant of the present application has proposed a multilayer laminated substrate having a structure in which coaxial via holes are formed around a via at a constant distance by laser processing and connected to a power supply and a ground layer in Japanese Patent Application No. 2001-23281. However, in these structures, there is a problem in that the manufacturing process becomes long and the cost increases because the structure is complicated or laser processing of multiple holes is required for forming the coaxial via.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a multilayer wiring board including a plurality of resin insulating layers and metal wiring layers,
The via hole shape of the hole for connecting the upper and lower metal wiring layers is arranged in a structure in which a via hole for signal transmission connecting to the signal transmission wiring is surrounded by a coaxial via hole to suppress electromagnetic radiation during signal transmission, An object of the present invention is to provide a via hole structure that reduces reflection and attenuation of signals during high frequency driving and a method for manufacturing the via hole structure.

[0008]

According to the invention of claim 1, in a multilayer wiring board in which insulating layers made of a resin insulating film and wiring layers made of a conductor film are alternately laminated, the wiring layers are connected to signal transmission wiring. The via hole is formed separately from the via hole and on the periphery of the via hole in a concentric circle separated by an insulating layer at regular intervals without being connected to the signal wiring layer, the power supply and the ground layer, and is embedded in the insulating resin layer. The multilayer wiring board with a coaxial via hole is characterized by having a coaxial via hole having the structure described above.

According to a second aspect of the present invention, there is provided the method of manufacturing a multilayer wiring board with coaxial via holes according to the first aspect, including the step (a) of forming a hole in the resin insulating film. (b) A step of forming a metal layer only on the side surface of the hole. (c) A process of filling holes with an adhesive, surface coating, and laminating metal foils on both sides. (d) A step of making a hole in the upper surface metal foil and the adhesive. (e) A step of forming a wiring pattern after performing via plating. (f) A step of attaching an insulating layer having a metal layer formed only on the side surface of the hole that can be produced in the steps (a) and (b) to the upper surface and the lower surface with an adhesive. The above steps (c) to (f) are repeated according to the number of stacked layers, and in the final stacking, the above (c) to (e) are carried out, and a method for manufacturing a multilayer wiring board with a coaxial via hole is provided. It is a thing.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a multilayer wiring board according to the present invention will be described below with reference to FIG. First, the insulating resin base material 11 is perforated (FIG. 2 (a)). By this drilling process, the hole 12 for forming the coaxial via is formed. A CO ₂ laser, an ultraviolet laser, an excimer laser, or the like can be used in the drilling process, but it is not limited to this. Next, a metal layer to be the coaxial via hole 13 is formed only on the side surface where the holes are formed (FIG. 2 (b)). As this method, it can be prepared by subjecting a perforated base material to electroless plating, electroplating, and then scraping off the metal layer of the surface layer using a technique such as physical polishing or chemical polishing.
Note that, depending on the shape of the metal layer inside the hole, it is also possible to control the shape by performing laser processing again with a diameter smaller than the diameter of the hole formed by the first laser. The metal layer formed on the side surface of the hole corresponds to the coaxial via hole 13.

Next, an adhesive is used to fill the holes and coat the surface (FIG. 2 (c)). As the adhesive 14, it is preferable to use a polyimide-based adhesive having excellent insulating properties and heat resistance, but this is not a limitation. The filling of the adhesive and the surface coating can be performed simultaneously by using a laminator. Next, using a laminator,
The metal foil 15 is attached to both upper and lower surfaces of the base material (FIG. 2 (d)).

Next, drilling is performed again (FIG. 2 (e)).
Process with a diameter smaller than the hole diameter drilled in Fig. 2 (a),
The signal transmission wiring hole 16 is formed. In the processing here,
Hole formation by blind hole processing (direct blind via processing) for metal penetration is required. In the case of direct blind via processing using copper as a metal, it is necessary for copper to absorb the energy of laser light, and a CO ₂ laser has to be subjected to blackening treatment or the like, which increases the production process. If the wavelength of the ultraviolet laser is equal to or higher than the third harmonic, the absorption wavelength of copper overlaps, and thus special treatment such as blackening can be omitted. A laser drilling machine that oscillates an ultraviolet laser wavelength of the third harmonic or higher is desirable. For example, the copper foil layer processing using an ultraviolet laser beam (third harmonic of a YAG crystal) is 10J / m ² or more, the resin layer processing 1~3J / m ²
It requires a certain amount of energy. Blind vias can be formed by utilizing this energy difference and irradiating the copper foil layer and the resin layer with the number of processable pulse shots.

Next, a filled via 17 (metal-filled via hole) is plated on the portion subjected to the direct blind via processing, and then a wiring layer 18 is formed on the upper and lower metal foils.
(Figure 2 (f)). Although filled vias are desirable from the viewpoint of high density, conformal vias (metal-coated via holes along the wall surface of the hole) may be used. A via hole can be formed by performing a desmearing treatment with permanganate after the drilling process and coating the inside of the hole with a metal substance such as a metal by an electrochemical method. At present, the subtractive method and the semi-additive method are considered as promising methods for forming the metal wiring layer. Also in the present invention, wiring can be formed by using either method. However, the forming method is not limited to these. Here, description will be given using a wiring forming method based on the subtractive method.
A resist is applied to a substrate, patterned by known photolithography, and etched with a chemical solution such as ferric chloride solution or cupric chloride using this resist as a mask. In order to increase production efficiency, it is desirable that exposure, development and etching be performed on both sides simultaneously.

Next, the base material 100 having a copper layer formed on the side surface of the hole for forming the coaxial via hole is attached to the upper and lower sides with an adhesive.
(Figure 2 (g)). After that, the above-described steps are repeated by the number of laminated layers to manufacture the multilayer wiring board with coaxial via holes according to the present invention. That is, the base material prepared in FIG. 2 (g) is filled with an adhesive and surface-coated, and then a metal foil is attached, a drilling process is performed, and then filled via plating and pattern formation are performed. 2 (h)
3 is an example of a four-layer structure of a coaxial multilayer wiring board according to the present invention.

Up to now, laser drilling has been used as a manufacturing method for forming the coaxial via hole hole and the via hole hole connected to the signal transmission wiring. However, the present invention is not limited to this, and the resin layer is used. When it has photosensitivity, the holes may be formed by known photolithography (photo via).

The method of manufacturing the multilayer wiring board with coaxial via holes according to the present invention is not limited to the above. The shape of the coaxial via hole and the method of manufacturing a multilayer wiring board using the same are the shape and the manufacturing method applicable to either a rigid or flexible wiring board.

[0017]

Example An evaluation substrate as shown in FIGS. 3 and 4 was prepared in order to measure the S parameter during high frequency transmission. FIG. 3 is a multilayer evaluation board with a coaxial via hole according to the present invention. The wiring length is 30 mm, and the coaxial via hole connecting the upper and lower wiring layers is
30 holes. Further, FIG. 4 shows an evaluation board having a single circular via hole, which was prepared for comparison with a coaxial via hole evaluation board. The wiring length is also 30 mm, and the via hole is 30
It's a hole. The insulating resin layer was polyimide having a thickness of 50 μm, and copper was used as the metal layer.

<Example> First, a method of manufacturing an evaluation substrate with a coaxial via hole (FIG. 3) according to the present invention will be described.
First, laser drilling was performed on the 30 μm thick polyimide tape substrate with the laser light of the third harmonic. The hole portion for forming the coaxial via hole had an arc diameter of φ100 μm. 3J / m ^{2 for} processing The hole for the coaxial via hole was formed by irradiating 30 pulses of the laser light.

After laser drilling, desmear treatment was performed for 5 minutes with an aqueous potassium permanganate solution. The desmearing treatment has the effect of removing the residue (smear) at the bottom of the hole and roughening the hole wall, increasing the plating adhesion strength in the next step. Then, through holes were plated on the side surfaces of the coaxial via hole portions to form the coaxial via holes. Chemical copper by self-catalytic electroless plating 0.2-0.5μ in the hole
m coating, copper sulfate 225g / L, sulfuric acid 55g / L, chloride ion 60mg / L
L, the additive was 20 mL, the bath temperature was 25 ° C., and the cathode current density was 1.0 A / dm ² for 15 minutes while stirring. The sample was dried at 90 ° C. for 10 minutes after electrolytic plating. The upper and lower copper layers were treated by physical polishing with buff roll. Through these steps, a copper layer having a thickness of 10 μm was formed.

Next, using a laminator, the polyimide adhesive was embedded in the holes and the upper and lower surfaces were simultaneously coated. The laminating conditions at this time are: laminating temperature 180 ° C., laminating pressure 0.2 MPa, laminator speed 1.0 m / min. And The thickness of the adhesive layer on the upper and lower surfaces was 10 μm. After embedding the adhesive in the holes and coating the surface, copper foil having a thickness of 12 μm was attached to the upper and lower surfaces using a laminator. The laminating conditions at this time are: laminating temperature 150 ° C., laminating pressure 0.1 MPa, laminator speed 1.0 m / min. And

After the copper foil was bonded, direct blind via processing was performed with a laser beam of the third harmonic. The hole for signal transmission has an arc diameter of φ50 μm. A hole for signal transmission was formed by irradiating 5 pulses of laser light with an energy density of 10 J / m ² for copper processing and 30 pulses of 3 J / m ² laser light for resin processing. After laser drilling, desmear treatment was performed with an aqueous potassium permanganate solution for 5 minutes.

Next, electrolytic copper plating was performed to perform filled via. The composition of the plating solution is copper sulfate 225g / L,
Sulfuric acid 55 g / L, chloride ion 60 mg / L, additive 20 mL, bath temperature 25 ° C, cathode current density 1.0 A / dm while stirring
50 minutes for ² minutes. The sample was dried at 90 ° C. for 10 minutes after electrolytic plating.

After that, a dry film resist (thickness 15
(μm) was thermocompression-bonded, patterned by photolithography (150 mJ / cm ² exposure, 1% sodium carbonate development), and etched with ferric chloride solution having a specific gravity of 1.35 and a liquid temperature of 45 ° C. Both patterning and etching of the dry film resist were performed on both sides simultaneously. Through the above steps, the wiring layers L1 and L2 in FIG. 3 were formed.

Next, a polyimide tape substrate with a copper foil on one side (copper foil thickness 12 μm, polyimide tape thickness 5
0 μm) was laminated with a thin film adhesive layer, and L3 was used as a ground layer. Through the above steps, an evaluation board of the multilayer wiring board with coaxial via holes according to the present invention shown in FIG. 3 was produced.

The S-parameter transmission (S21) at the time of high frequency signal transmission was measured on the manufactured evaluation board using an Agilent Technologies 8722ES Network Analyzer. The results are shown in Table 1. During high frequency signal transmission (30-40GH
It can be seen that even in the z band), a signal can be transmitted with about 10% attenuation.

<Comparative Example> A method of manufacturing an evaluation substrate (FIG. 4) having a single circular via hole will be described. First, direct blind via processing was performed on the polyimide tape with double-sided copper foil (copper foil thickness 12 μm, polyimide tape thickness 50 μm) by the third harmonic laser light. The hole for signal transmission has an arc diameter of φ50 μm. Energy density for copper processing
The signal transmission holes were formed by irradiating 5 pulses of 10 J / m ² laser light and 30 pulses of 3 J / m ² laser light for resin processing. After laser drilling, desmear treatment was performed with an aqueous potassium permanganate solution for 5 minutes.

Next, electrolytic copper plating was performed thereafter to perform filled via. The composition of the plating solution is copper sulfate 225g / L,
Sulfuric acid 55 g / L, chloride ion 60 mg / L, additive 20 mL, bath temperature 25 ° C, cathode current density 1.0 A / dm while stirring
50 minutes for ² minutes. The sample was dried at 90 ° C. for 10 minutes after electrolytic plating.

After that, a dry film resist (thickness 15
(μm) was thermocompression-bonded, patterned by photolithography (150 mJ / cm ² exposure, 1% sodium carbonate development), and etched with ferric chloride solution having a specific gravity of 1.35 and a liquid temperature of 45 ° C. Both patterning and etching of the dry film resist were performed on both sides simultaneously. Through the above steps, the wiring layers of L'1 and L'2 in FIGS. 3 and 4 were formed.

Next, a polyimide tape substrate (copper foil thickness 12 μm, polyimide tape thickness 5
0 μm) was laminated via a thin film adhesive layer, and L′ 3 was used as a ground layer. Through the above steps, an evaluation board of the multilayer wiring board with coaxial via holes according to the present invention shown in FIG. 3 was produced.

The S-parameter transmission (S21) at the time of high frequency signal transmission was measured on the produced evaluation board using an Agilent Technologies 8722ES Network Analyzer. The results are shown in Table 1. During high frequency signal transmission (30-40GH
It can be seen that there is a large attenuation of about 50% in the z band).

[0031]

【table 1】

[0032]

According to the multilayer wiring board with coaxial via holes of the present invention, a high-frequency signal, which has a very large attenuation in a single circular via hole, can be transmitted with 60 to 80% less attenuation. Further, when driving at a higher frequency, a difference appears in the attenuation of signal transmission between the coaxial via hole and the single circular via hole. The multilayer wiring board with a coaxial via hole according to the present invention,
This is a via-hole structure and a multilayer wiring board that will respond to the trend of higher frequency driving of semiconductors in the future. Further, according to the method of manufacturing a multilayer wiring board with a coaxial via hole according to the present invention, it is possible to provide a manufacturing method capable of reducing cost by reducing the number of manufacturing steps and processing time for forming the coaxial via hole.

[0033]

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a wiring structure having a signal transmission wiring, a power supply, and a ground wiring (layer).

FIG. 2 is an example of a method for manufacturing a multilayer wiring board with coaxial via holes according to the present invention.

3A and 3B are a top view and a cross-sectional view of an evaluation board of a coaxial via-hole multilayer wiring board according to the present invention.

FIG. 4 is a top view and a cross-sectional view of an evaluation board of a multilayer wiring board having via holes on a single circle.

[Explanation of symbols]

1 signal transmission wiring 2 insulating resin 3 lower surface power supply and ground layer 4 upper surface power supply and ground layer 5 power supply and ground wiring 11 insulating resin base material 12 coaxial via hole forming hole 13 coaxial via hole 14 adhesive 15 copper foil 16 for signal transmission wiring Hole 17 Filled via 18 Signal transmission wiring layer 100 Coaxial via hole forming base material with copper layer formed on the side surface

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05K 3/42 620 H05K 3/42 620A (72) Inventor Katsumi Makino 1-5-1 Taito, Taito-ku, Tokyo No. Toppan Printing Co., Ltd. (72) Inventor Kento Tsukamoto 1-5-1, Taito, Taito-ku, Tokyo F-Term within Toppan Printing Co., Ltd. (reference) 5E314 AA25 AA36 BB02 CC15 DD02 DD07 EE03 FF05 FF16 GG24 GG26 5E317 AA21 AA24 BB03 BB12 CC32 CC33 CD05 CD25 CD27 CD32 GG11 GG17 5E346 AA02 AA12 AA43 BB02 CC10 CC32 CC41 CC55 CC58 DD02 DD12 DD32 DD44 EE33 FF03 FF07 FF15 GG15 GG17 GG22 GG27 GG28 HH06 HH32

Claims (2)

[Claims] 1. In a multilayer wiring board in which an insulating layer made of a resin insulating film and a wiring layer made of a conductor film are alternately laminated, a via hole connected to a signal transmission wiring and a constant space around the via hole. Is coaxially separated by an insulating layer and is coaxially formed independently without being connected to the signal wiring layer, the power source, and the ground layer, and has a coaxial via hole having a structure embedded in the insulating resin layer. Multilayer wiring board with coaxial via holes. 2. The method of manufacturing a multilayer wiring board with a coaxial via hole according to claim 1, wherein (a) a step of forming a hole in the resin insulating film. (b) A step of forming a metal layer only on the side surface of the hole. (c) A process of filling holes with an adhesive, surface coating, and laminating metal foils on both sides. (d) A step of making a hole in the upper surface metal foil and the adhesive. (e) A step of forming a wiring pattern after performing via plating. (f) A step of attaching an insulating layer having a metal layer formed only on the side surface of the hole that can be produced in the steps (a) and (b) to the upper surface and the lower surface with an adhesive. A method for manufacturing a multilayer wiring board with a coaxial via hole, which comprises repeating the steps (c) to (f) according to the number of stacked layers and performing steps (c) to (e) in the final stacking.