JPS6250076B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for simply and economically manufacturing a multilayer printed wiring board with excellent heat resistance reliability and wiring accommodation capacity. Conventionally, in order to increase the number of wires that can be accommodated in printed wiring boards, multilayering using a plated through-hole method has been widely applied. A multilayer printed wiring board using this technology is produced by heat-pressing a plurality of printed wiring boards on which printed circuits are formed via prepreg to create a laminate having inner layer circuits and surface layer circuits, and then attaching the laminate to a predetermined position on the laminate. It is manufactured by forming through-hole holes with a drill and plating the holes to electrically connect circuits between both layers. The multilayer printed wiring board manufactured by the above method is
As the degree of integration of integrated devices improves, there is a need for a significant increase in the number of wires that can be accommodated, and the number of layers tends to increase year by year. However, as the number of layers increases, the number of through holes for interlayer connections increases, and the wiring area of the flat plate decreases, so even if the number of layers increases, the number of wires accommodated cannot be improved much. Therefore, it is necessary to reduce the diameter of the through-hole, but as the number of layers increases, the substrate becomes thicker, resulting in disadvantages such as poor hole machinability and poor blinding ability. Therefore, as the number of wires accommodated increases, the manufacturing yield is extremely reduced, which is a major problem. In addition, when an integrated element is changed, the pattern of the printed wiring board on which it is mounted may be required to be changed, but this pattern change is difficult with drilling-based manufacturing technology for multilayer wiring boards, so it is difficult to change the pattern from the beginning. It is very uneconomical because it has to be remade. On the other hand, various heat-resistant energy-sensitive resin compositions have been developed, but they only dissolve in high-boiling point solvents, but their molecular weight is low before curing.
Cannot be made into dry film. Therefore, it is dissolved in a suitable solvent, applied to a printed circuit by spinner coating, dipping, etc., and dried. For this reason, the workability is significantly reduced, such as the danger in handling the organic solvent and the time required for drying. Moreover, various dry films such as solder masks have a low glass transition temperature and a large coefficient of linear expansion even after curing. Therefore, when used as an insulating material for printed wiring boards, it has the disadvantage that it expands due to the heat generated from the mounted elements and breaks the circuit conductor. The present invention has been made in view of the above circumstances, and its purpose is to provide a method for easily and economically manufacturing a multilayer printed wiring board with excellent wiring accommodation capacity and high heat resistance and reliability. . That is, to summarize the present invention, the present invention provides the following general formula: [In the formula, R ₁ is the same or different, and

【formula】

【formula】

[Formula] or

[Formula] (Y and Z are the same or different and represent a hydrogen atom, a lower alkyl group, or a phenyl group)
, R ₂ are the same or different, and the formula: (However, U and V are the same or different and represent a hydrogen atom or a methyl group), X is the same or different and represents a hydrogen atom, a chlorine atom, or a bromine atom, and n represents a positive integer] A step of providing an energy ray-sensitive polymer layer containing a polymer represented by A step of heat-treating or irradiating the combined layer with energy rays to make it highly insulating, forming a conductor circuit by plating on this highly insulating polymer layer, and passing the conductor circuit through the through hole to connect the printed wiring. The present invention relates to a method for manufacturing a multilayer printed wiring board, which includes the steps of electrically connecting a printed circuit on a substrate. Hereinafter, the present invention will be explained in detail with reference to the drawings. 1A to 1F are schematic cross-sectional views showing the manufacturing process of the multilayer printed wiring board of the present invention, and FIG. 2 is a schematic cross-sectional view showing the process of directly irradiating the energy ray-sensitive polymer layer with energy rays. be. In the figure, 1 is an insulating substrate, 2 is a printed circuit, 3 is a printed wiring board, 4 is an energy-sensitive polymer layer, 5 is a photomask, 6 is an energy ray source, 7 is a hole for a through hole, and 8 is an active 9 indicates a conductor circuit, and 10 indicates a conductor layer. First, as shown in FIG. 1a, a printed circuit board 3 is fabricated by forming a printed circuit 2 on an insulating substrate 1 made of a glass cloth base material, polyimide resin, etc. in accordance with a conventional method. The printed wiring board used here may be a multilayer printed wiring board. Next, an energy ray-sensitive polymer layer 4 mainly composed of a polymer represented by the above general formula is formed on the entire surface of the printed wiring board 3 on the printed circuit 2 side.
Figure b]. A typical method for producing a polymer represented by the above general formula is as follows: (However, in the formula, R ₁ and X are as in the above formula)
and epichlorohydrin, and the resulting polymer has the general formula: (However, U and V in the formula are as in the above formula)
can be obtained by reacting in the presence of a catalyst. In addition, when using light such as ultraviolet rays as energy rays in the energy ray irradiation described later, it is desirable to further sensitize the photoreaction by adding a sensitizer. As such sensitizers, carbonyl compounds such as acetophenone, benzophenone, dimethylaminobenzophenone, and benzoin isopropyl ether are effective, and furthermore, as spectral sensitizers, 5-nitroacenaphthene and 1-
Compounds such as nitropyrene are also effective. The amount of these compounds added is suitably 0.1 to 10% by weight based on the polymer. It is also effective to add a crosslinking agent such as an aromatic tetrazo compound, an aromatic bisazide compound, or a polyfunctional vinyl compound in order to increase the crosslinking density, but in order not to increase the linear expansion coefficient of the insulating film, the above 1 to 20% by weight of the polymer is preferred. In forming the energy ray-sensitive polymer layer 4, for example, the polymer or the sensitizer and crosslinking agent added as necessary are dissolved in an appropriate solvent,
This liquid is applied onto a flexible support film, such as a polyester film, and dried, and a polyethylene cover sheet is provided thereon to prepare a dry film with a sandwich structure in advance.
The polyethylene cover sheet of this dry film is peeled off, a support film is placed on the printed wiring board so that the energy ray-sensitive polymer layer made of the above polymer is in contact with the printed wiring board, and the support film is laminated with a hot roll laminator. The polyester film may be left as is or may be peeled off during the energy ray irradiation described later. The thickness of the energy ray-sensitive polymer layer 4 thus formed is desirably 50 μm or more in view of the characteristic impedance of the printed wiring board. Other methods of coating the substrate include screen printing. Next, as shown in FIG. 1c, the energy ray-sensitive polymer layer 4 is selectively irradiated with energy rays through the mask 5. In this case, energy rays may be selectively and directly irradiated from an energy ray source to the energy ray sensitive polymer layer 4 as shown in FIG. By selectively irradiating the energy rays, the polymer layer 4
The irradiated part becomes insoluble in the solvent, and the unirradiated part remains soluble in the solvent. Examples of such energy rays include visible light, ultraviolet rays, X-rays, laser light, and electron beams. Next, by developing the energy ray-sensitive polymer layer 4, the unirradiated portions of the polymer layer 4 are eluted into a solvent to form through-hole holes 7 (FIG. 1d). Examples of the developer used here include organic solvents such as 1,1,1-trichloroethane. Next, the polymer layer 4 provided with the through-hole holes 7 is subjected to heat treatment or the entire surface is exposed to energy rays to achieve high insulation. Next, the highly insulating polymer layer 4 is subjected to liquid honing or plasma etching to roughen the surface of the polymer layer 4 and improve the wettability of the through holes, and then organic acid silver or the like is applied. and photomask etc. (not shown)
The plating active layer 8 is formed by exposing the area where the conductor circuit is to be formed and developing it.
Figure e]. Next, electroless plating is applied to form a plating active layer 8.
A conductor circuit 9 is formed on the top, a conductor layer 10 is formed in the through-hole hole 7, and a part of the conductor circuit 9 is connected to a part of the printed circuit 2 of the printed wiring board 3 to form a two-layer printed wiring board. Fabricate [Fig. 1 f]. Thereafter, a multilayer printed wiring board having three or more layers is manufactured by repeating the same operation. According to the method of the present invention, an energy ray-sensitive polymer layer containing a polymer represented by the general formula as a main component is provided on a printed wiring board with a printed circuit formed on the surface of an insulating substrate, and this layer is coated with a photomask. Fine holes for through-holes can be easily formed by irradiating energy rays through or directly with energy rays and developing. Subsequently, the energy ray-sensitive polymer layer after the hole formation is subjected to heat treatment or energy ray irradiation treatment to increase the insulation of the layer.
It is possible to form a highly insulating polymer layer that corresponds to a conventional prepreg layer and has characteristics such as excellent adhesion to an insulating substrate and heat resistance, and a small coefficient of linear expansion. Next, the surface of the layer is roughened by liquid honing or plasma etching, etc., and the wettability of the layer surface and the inside of the through hole is improved. Then, an activation treatment is performed using an organic acid silver salt, etc., to form an electroless layer. A two-layer printed wiring board can be created by forming a conductive circuit by perforating the conductive circuit and electrically connecting it to a printed circuit on the board through the through-hole. By further forming the energy ray-sensitive polymer layer thereon and repeating the same operations as above, a printed wiring board having a multilayer structure of three or more layers can be efficiently manufactured. In the multilayer printed wiring board produced in this manner, the diameter of the through-hole is smaller than in the case of conventional drilling, so the number of wires that can be accommodated can be greatly increased. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. Example Phenoxy resin synthesized from bisphenol A and epichlorohydrin [Scientific
Scientific Polymer Products
Products) (weight average molecular weight 3.2×10 ⁴ )] 56g
was heated and dissolved in 260 g of glycidyl methacrylate at 75 to 95°C, and 0.85 g of triethylbenzylammonium chloride was added as a catalyst to this for 4 hours.
The mixture was stirred and reacted at ~95°C. This reaction solution was poured into methanol 20 to obtain a phenoxy resin into which a glycidyl methacrylate residue was introduced. 100 g of this phenoxy resin, 0.2 g of dimethylaminobenzophenone, and 6 g of benzoin isopropyl ether were dissolved in 1 part of tetrahydrofuran, coated on a 1 m x 1 m polyester film, dried, and covered with a polyethylene film.
A dry film of 80 μm was obtained by forming a sandwich structure. The dry film obtained by the above method is heat-pressed using a hot roll laminator onto a printed wiring board obtained by photoetching the surface copper foil of a copper-clad laminate (glass cloth base polyimide resin) by a conventional method. Evenly coated. Next, a photomask with a 0.10mmφ black circle formed on a 1.25mm grid was attached closely to this and exposed using a 3K.W. ultra-high pressure mercury lamp.
Exposure was made for 20 seconds. This was developed with 1.1.1-trichloroethane for 1 minute using ultrasonic waves to obtain the above polymer layer in which holes with a diameter of 0.10 mm were formed in a 1.25 mm grid on a printed wiring board. Next, this substrate was heat-treated at 200° C. for 30 minutes in vacuum to make the layer highly insulating. Next, the surface of the layer and the inside of the holes were roughened by liquid honing (2 Kg/cm ² ). Next, a 10% silver glutamate aqueous solution was applied to this, and after drying, it was exposed to an ultra-high pressure mercury lamp through a photomask to deposit silver, which will become the nucleus of copper plating, only on the parts that will become the circuit, and then a 10% ammonia aqueous solution was applied. The unexposed silver glutamate was eluted. Next, it was immersed in an electroless plating solution (CP-78 manufactured by Shippray Co., Ltd.) to deposit copper plating to a thickness of 25 μm on the silver pattern to obtain a two-layer printed wiring board. Furthermore, using the dry film above, perform the same operation as above 3 times.
A five-layer printed wiring board was created by repeating the process several times.
In addition, for comparison, printed wiring boards with through-holes formed using conventional drilling techniques were created, and various circuit characteristics of both were investigated. The results are shown in Table 1 below.

[Table] As is clear from the above table, in the present invention, the diameter of the through hole formed is smaller than that in the case of conventional drilling, so according to the present invention, the number of patterns accommodated is significantly increased. A multilayer printed wiring board can be obtained. Furthermore, the linear expansion coefficient of the dry film used in the present invention after heat treatment is 7×
The multilayer printed wiring board produced by the present invention has an extremely low temperature of 10 ^-5 /℃ and therefore has good dimensional stability.
Even after heating at ℃ for 2 hours and then rapidly cooling to 0℃, no abnormalities such as circuit breakage or insulation layer breakdown were observed. In addition, in the results using conventional technology, for example, an acrylic photocrosslinkable polymer film (SR-1000 manufactured by Hitachi Chemical, thickness 0.075 mm), the coefficient of linear expansion after crosslinking was as high as 5 × 10 ^-4 /°C; Therefore 200℃30
When it was rapidly cooled to 0° C. after heating for 30 minutes, the through hole broke. Furthermore, in place of the phenoxy resin used as a raw material in the above example, a phenoxy resin synthesized from tetrabromobisphenol A and epichlorohydrin was used, and almost the same results were obtained. As explained in detail above, the method for manufacturing a multilayer printed wiring board according to the present invention has excellent pattern accommodation capacity, so that the total pattern wiring amount of the multilayer printed wiring board by drilling can be reduced to 1/3 to 1/5 of the number of layers. It is possible to accommodate a large amount of fuel, and together with the reduction of manufacturing steps and the improvement of yield, it is possible to significantly reduce manufacturing costs. In addition, the multilayer printed wiring board obtained by the present invention has high heat resistance and excellent dimensional stability, so even when elements that generate a lot of heat are mounted, circuit patterns etc. will not break due to expansion of the insulating layer. This makes it extremely reliable. Furthermore, it is also possible to apply the manufacturing method of the present invention only to parts of printed wiring boards that require high-density wiring (for example, parts where highly integrated elements such as ultra-LSI are mounted), and it is possible to change the integrated elements. It is extremely economical because it can easily handle circuit changes due to

[Brief explanation of the drawing]

1A to 1F are schematic cross-sectional views showing the manufacturing process of the multilayer printed wiring board of the present invention, and FIG. 2 is a schematic cross-sectional view showing the process of directly irradiating the energy ray-sensitive polymer layer with energy rays. 1: Insulating substrate, 2: Printed circuit, 3: Printed wiring board, 4: Energy ray sensitive polymer layer, 5: Photomask, 6: Energy ray source, 7: Hole for through hole, 8: Active layer, 9: Conductor Circuit, 10: conductor layer.

Claims (1)

[Claims] 1. On a printed wiring board on which a printed circuit is formed, the following general formula: [In the formula, R ₁ is the same or different, and [Formula] [Formula] [Formula] or [Formula] (However, Y and Z are the same or different and represent a hydrogen atom, a lower alkyl group, or a phenyl group)
, R ₂ are the same or different, and the formula: (However, U and V are the same or different and represent a hydrogen atom or a methyl group), X is the same or different and represents a hydrogen atom, a chlorine atom, or a bromine atom, and n represents a positive integer] A step of providing an energy ray-sensitive polymer layer containing a polymer represented by A step of heat-treating or irradiating the combined layer with energy rays to make it highly insulating, forming a conductor circuit by plating on this highly insulating polymer layer, and passing the conductor circuit through the through hole to connect the printed wiring. 1. A method for manufacturing a multilayer printed wiring board, comprising the steps of electrically connecting a printed circuit on a substrate.