JP2001185844A - Printed wiring board and producing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board with which layers are connected by using conductive paste, improved in density and reliability, and a method for efficiently producing such a printed wiring board. SOLUTION: Concerning the printed wiring board for connecting conductor layers by using the conductive paste, the land of an inner layer board corresponding to a via hole filled with the conductive paste is thicker than other circuit conductors more than 5 μm. The producing method for printed wiring board is composed of a process for thinning metal foil more than 5 μm except for the land scheduled part of the inner layer circuit board, process for forming a conductor pattern by working the metal foil, process or boring a hole from the side of an adhesive layer to the metal foil at a desired spot on the metal foil with adhesive layer and filling that hole with the conductive paste, process for piling the metal foil with adhesive layer filled with the conductive paste on the surface of the inner layer circuit with the metal foil outside, laminating and integrating them by pressing/heating, and process for forming the conductor pattern by working the outside metal foil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a printed wiring board and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the miniaturization, high performance, and multifunctionality of electronic devices, multilayer printed wiring boards have been required to have higher densities. In order to satisfy these requirements, thinning between layers, miniaturization of wiring, miniaturization of interlayer connection holes have been performed, and via holes for connecting only conductors between adjacent layers have been used. It is getting smaller. For multi-layer wiring,
A plurality of circuit layers and an interlayer insulating layer between them are collectively overlapped, pressurized, heated and laminated and integrated, and a multilayer wiring board for making holes and connecting at required locations, and forming an interlayer insulating layer on a circuit. Forming, forming a circuit on it, providing holes where needed,
There is a build-up multilayer wiring board in which a circuit layer and an insulating layer are sequentially formed.

As one method of manufacturing this build-up multilayer wiring board, a hole formed in an adhesive layer is filled with a conductive paste, and an inner layer circuit board is pressed and heated to form an outer layer circuit formed in the adhesive layer. There is a method of electrically connecting. Thereafter, if necessary, the same steps as described above are repeated to form a required multilayer circuit.

[0004] As disclosed in Japanese Patent No. 26001128, a conductive paste having a relatively small content of a conductive substance and excellent in printability is filled in a through hole of a compressible porous base material, The binder component in the conductive paste penetrates into the pores of the compressible porous substrate during the heating and pressurizing step, thereby increasing the composition ratio of the conductive material in the conductive paste, thereby providing highly reliable printing. A method capable of providing a wiring board has been proposed.

[0005]

However, Patent No. 260
In the method disclosed in Japanese Patent No. 1128, a special material called a compressible porous base material must be used, and the drilling conditions and handling are different from those of ordinary materials for printed wiring boards, so that the production is efficient. In addition, there is a problem that a special adhesive must be used because the adhesive is porous.

[0006] The present invention provides a printed wiring board having a high-density and high-reliability connection between layers using a conductive paste,
An object of the present invention is to provide a method for efficiently manufacturing such a printed wiring board.

[0007]

The present invention is characterized by the following. (1) In a printed wiring board in which connection between conductive layers is performed using a conductive paste, the land thickness of the inner layer plate corresponding to the via hole filled with the conductive paste is at least 5 μm thicker than other circuit conductors. Printed wiring board. (2) A method for manufacturing a printed wiring board, comprising the following steps. (A) 5 μm of metal foil other than the planned land portion of the inner layer circuit board
(B) Step of processing a metal foil to form a conductor pattern (c) Drilling a hole reaching the metal foil from the adhesive layer side at a desired location of the metal foil with an adhesive layer, Step of filling paste (d) Step of stacking a metal foil with an adhesive layer filled with a conductive paste on the surface of the inner circuit board so that the metal foil is on the outside, and pressing and heating to laminate and integrate ( e) a step of forming a conductor pattern by processing an outer metal foil (3) A method for manufacturing a printed wiring board, comprising the following steps. (A1) 5 μm of only the metal foil at the planned land portion of the inner layer circuit board
(b) Step of forming a conductive pattern by processing a metal foil (c) Drilling a hole reaching the metal foil from the adhesive layer side at a desired position of the metal foil with an adhesive layer, and conducting the conductive hole in the hole (D) a step of stacking a metal foil with an adhesive layer filled with a conductive paste on the surface of an inner circuit board so that the metal foil is on the outside, and pressing and heating to laminate and integrate (E) Processing the outer metal foil to form a conductor pattern (4) Using the printed wiring board produced in the step (d) as the inner layer circuit board in the step (a) or (a1) (2) The method for producing a printed wiring board according to (3).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the conductive paste of the present invention, a paste containing conductive particles and a resin as main components can be used. Silver or copper, copper whose surface is coated with silver, or the like can be used as the conductive particles of the conductive paste. As the resin, an epoxy resin, a phenol resin, a polyimide resin, a polyamideimide resin, or the like can be used.

As the adhesive layer, those containing epoxy or polyimide as a component can be used, and an epoxy adhesive film containing a high molecular weight epoxy polymer having a molecular weight of 100,000 or more as a main component, and an epoxy adhesive film containing a modified rubber. And polyimide-based adhesive films, and epoxy-based adhesive films in which a fibrous substance having a diameter of 1.0 μm to 6 μm and a length of 5 μm to 1 mm are dispersed in an epoxy resin.

(Step a) The metal foil used is preferably a copper foil in terms of efficiency and economy. In order to reduce the thickness of the metal foil other than the intended land portion of the inner layer circuit board by 5 μm or more, an etching resist is formed in the shape of the land, and a portion not covered with the etching resist is brought into contact with a chemical etching solution. Thin the metal foil. In this case, as a chemical etching solution that can be used, there is Permaetch (trade name, Ebara Densan Co., Ltd.) or SE-07 liquid (trade name, Mitsubishi Gas Chemical Co., Ltd.). The thickness of the metal foil after the etching is 5 points in view of electrical characteristics and formation of a fine circuit.
To 25 μm, more preferably 9 to 20 μm
Is good. Further, the thickness of the metal foil in the land portion is preferably 10 μm or more, more preferably 30 μm or more, from the viewpoint of connection reliability with the conductive paste in the via hole. By compressing the conductive paste in the via at the inner layer land during the laminating press, the compressibility of the conductive paste in the via is increased, thereby lowering the specific resistance of the conductive paste in each via and the connection reliability. Can be improved.

(Step a1) The metal foil used is preferably a copper foil from the viewpoint of efficiency and economy. In order to increase the thickness of only the metal foil of the intended land portion of the inner layer circuit board by 5 μm or more, a plating resist is formed in a portion other than the land portion, and a portion not covered with the resist is brought into contact with an electrolytic copper plating solution.
Thicken the metal foil. In this case, the copper electroplating solution that can be used includes a copper sulfate plating solution generally used for printed wiring boards. The thickness of the metal foil in the circuit portion is preferably from 5 to 25 μm, more preferably from 9 to 20 μm, from the viewpoint of electrical characteristics and formation of a fine circuit. Further, the thickness of the metal foil in the land portion is preferably 10 μm or more, more preferably 30 μm or more, from the viewpoint of connection reliability with the conductive paste in the via hole. Therefore, the difference between the thickness of the metal foil of the land portion and the thickness of the metal foil of the conductor circuit portion is 5 μm or more, preferably 1 μm or more.
0 μm or more is good.

(Step c) In order to form a hole reaching the metal foil, it is preferable to use a laser, and an excimer laser or a carbon dioxide laser can be used as the laser. Lasers are preferred.

(Step d) To laminate a metal foil with an adhesive layer filled with a conductive paste on the surface of the inner layer circuit board so that the metal foil is on the outside and press and heat to laminate and integrate The lamination technique used for ordinary multilayer printed wiring boards can be used as it is. Generally, the temperature is 160-18
The conditions are 5 ° C., a pressure of 1 to 5 MPa, and a time of about 30 to 120 minutes.

(Steps b and e) In order to form a conductive pattern by processing the outer metal foil, an etching resist is formed in the shape of a circuit, and a portion not covered with the etching resist is subjected to a chemical etching solution. , The metal foil can be selectively removed to form a circuit.

[0015]

EXAMPLES Example 1 (Steps a1 and b for Producing an Inner Circuit Board)
mm, a copper foil 18 μm thick glass cloth-epoxy resin impregnated double-sided copper-clad laminate MCL-679 (trade name, manufactured by Hitachi Chemical Co., Ltd.), and a dry film HK-
Using 450 (manufactured by Hitachi Chemical Co., Ltd., trade name), a resist pattern for plating was formed, and then electro-copper plating was performed so that the thickness of the copper layer was reduced to 35 μm only at the planned lands. Then, etching resist film HK-425
(Made by Hitachi Chemical Co., Ltd., trade name)
A photomask is overlaid, irradiated with ultraviolet light, developed to form an etching resist, and unnecessary portions of the copper foil are removed by etching. Minimum line / space = 70 μm / 70 μm
Was formed to produce an inner circuit board.

(Step c) A copper foil having a thickness of 18 μm
MCF-600 provided with a 0 μm epoxy adhesive layer
0E (trade name, manufactured by Hitachi Chemical Co., Ltd.), a carbon dioxide impact laser was applied from the side of the adhesive layer of the metal foil with the adhesive layer in which a 25 μm-thick polyethylene terephthalate film was adhered to the surface of the adhesive layer with a roll laminator. Laser light is irradiated by a drilling machine L-500 (trade name, manufactured by Sumitomo Heavy Industries, Ltd.) under the conditions of frequency = 150 Hz, voltage = 20 kV, pulse energy = 85 mJ, number of shots = 7 shots, and interlayer connection is performed. The resin was removed from the portion to be removed, and a hole having a diameter of 0.15 mm reaching the copper foil was formed. A conductive paste N is applied to the perforated metal foil with adhesive layer.
F2000 (trade name, manufactured by Tatsuta Electric Wire Co., Ltd.) was filled from above the surface of the polyethylene terephthalate film by a screen printing method. The metal foil with an adhesive layer filled with the conductive paste was heated at 110 ° C. for 15 minutes. further,
The polyethylene terephthalate film was peeled off.

(Step d) A metal foil with an adhesive layer was laminated on the inner circuit board, and laminated and integrated under the conditions of a pressure of 2.94 MPa, a temperature of 175 ° C. and 90 minutes to obtain a laminate.

(Step e) An etching resist film HK-425 (trade name, manufactured by Hitachi Chemical Co., Ltd.) is laminated on both sides of the laminate, a photomask is overlaid, ultraviolet rays are irradiated and developed, and the etching resist is developed. Forming
Unnecessary copper was removed by etching to form an outer layer circuit, and a printed wiring board was manufactured.

Example 2 (Steps a1 and b for Producing an Inner-Layer Circuit Board)
MCL-679 (trade name, manufactured by Hitachi Chemical Co., Ltd.), a glass cloth-epoxy resin impregnated double-sided copper-clad laminate with a thickness of 35 mm and a copper foil thickness of 35 μm, and then etching resist was applied only to the planned land portions Formed, using SE-07 liquid (Mitsubishi Gas Chemical Co., Ltd., trade name), copper thickness 15 ~ 2
The copper was etched to 0 μm. Subsequently, an etching resist film HK-425 (trade name, manufactured by Hitachi Chemical Co., Ltd.) is laminated, a photomask is superimposed, ultraviolet irradiation is performed, and development is performed to form an etching resist. By etching away, an inner layer circuit having a minimum line / space of 70 μm / 70 μm was formed, and an inner layer circuit board was manufactured. (Step c), (Step d),
(Step e) was performed in the same manner as in Example 1 to produce a printed wiring board.

Comparative Example 1 (Steps a and b for Producing an Inner-Layer Circuit Board)
m, MCL-679 (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is a double-sided copper-clad laminate impregnated with a glass cloth having a copper foil thickness of 35 μm. Minimum line / space = 70 μm by the same method as in Example 2 except that the copper is etched so as to reduce the thickness of the copper except for the planned land using SE-07 liquid (Mitsubishi Gas Chemical Co., Ltd., trade name).
An inner layer circuit of m / 70 μm was formed, and an inner layer circuit board was produced. (Step c), (Step d), and (Step e) were performed in the same manner as in Example 1 to produce a printed wiring board.

Comparative Example 2 (Steps a1 and b for Producing Inner Circuit Board)
MCL-679 (trade name, manufactured by Hitachi Chemical Co., Ltd.), a glass cloth-epoxy resin-impregnated double-sided copper-clad laminate having a thickness of 18 mm and a copper foil thickness of 18 μm, was used. An inner layer circuit having a minimum line / space = 70 μm / 70 μm was formed in the same manner as in Example 1 except that a resist pattern for plating was formed, electrolytic copper plating was performed, and the copper layer was thickened only at the planned land portion. An inner circuit board was produced. (Step c),
(Step d) and (Step e) were performed in the same manner as in Example 1 to produce a printed wiring board.

The appearance of the inner layer circuit boards of the printed wiring boards of these examples and comparative examples was inspected to determine the circuit failure rate (details of failure: short circuit, small circuit width, etc.). Further, the conduction resistance of these printed wiring boards is a state in which 400 vias are connected in series, and the initial value of these is measured.
The resistance value when immersed 200 times at 0 seconds was measured, and the rate of change of the resistance value after the test was determined. Table 2 shows the results.

[0023]

[Table 1]

As shown in the table, Examples 1 and 2
In both cases, the circuit failure rate was 0%, and the change rate of the resistance value was 5% or less, and the characteristics were good.

[0025]

As described above, according to the present invention, a printed wiring board having a high-density and excellent reliability, in which layers are connected by a conductive paste, and a method for efficiently manufacturing such a printed wiring board. Can be provided.

Continued on the front page F term (reference) 5E317 AA24 CC22 CC25 CC53 GG11 5E343 AA02 AA12 BB08 BB14 BB24 BB67 EE52 EE58 ER11 ER51 GG13 5E346 AA12 AA15 AA43 BB01 BB15 BB16 CC31 CC32 CC58 EE02 GG22 GG18 GG02 GG18

Claims (4)

[Claims] 1. A printed wiring board for connecting between conductive layers using a conductive paste, wherein a land thickness of an inner layer plate corresponding to a via hole filled with the conductive paste is at least 5 μm thicker than other circuit conductors. And printed wiring board. 2. A method for manufacturing a printed wiring board, comprising the following steps. (A) 5 μm of metal foil other than the planned land portion of the inner layer circuit board
(B) Step of processing a metal foil to form a conductor pattern (c) Drilling a hole reaching the metal foil from the adhesive layer side at a desired location of the metal foil with an adhesive layer, Step of filling paste (d) Step of stacking a metal foil with an adhesive layer filled with a conductive paste on the surface of the inner circuit board so that the metal foil is on the outside, and pressing and heating to laminate and integrate ( e) a step of processing the outer metal foil to form a conductor pattern 3. A method for manufacturing a printed wiring board, comprising the following steps. (A1) 5 μm of only the metal foil at the planned land portion of the inner layer circuit board
(b) Step of forming a conductive pattern by processing a metal foil (c) Drilling a hole reaching the metal foil from the adhesive layer side at a desired position of the metal foil with an adhesive layer, and conducting the conductive hole in the hole (D) a step of stacking a metal foil with an adhesive layer filled with a conductive paste on the surface of an inner circuit board so that the metal foil is on the outside, and pressing and heating to laminate and integrate (E) forming a conductor pattern by processing the outer metal foil; 4. The method for producing a printed wiring board according to claim 2, wherein the printed wiring board produced in the step (d) is used as an inner layer circuit board in the step (a) or (a1).