JPH021392B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a method for manufacturing a multilayer printed wiring board, and particularly to a method for manufacturing an inner layer of a multilayer printed wiring board. (Prior Art) In recent years, as electronic components such as ICs and LSIs mounted on printed wiring boards have become faster and more dense, the supply of power consumed by these electronic components has become a problem. For this reason, there is a trend to gradually increase the thickness of copper foil used for the inner conductor layer of multilayer printed wiring boards to improve power supply. In other words, in general, thin copper foil with a thickness of 35 to 70 μm was used for the power supply layer and ground layer as inner conductor layers, but power supply was improved by using thicker copper foil with a thickness of 150 to 300 μm or more. I've come to do it. A method of manufacturing a multilayer printed wiring board using a thick inner conductor layer using a conventional method will be explained with reference to FIGS. 1A to 1M. First, in FIG. 1A, a thick metal foil 2 is placed on an insulating substrate 1.
FIG. 2 is a cross-sectional view of a double-sided metal foil-clad insulating board with parts a and 2b bonded together. Here, the metal foils 2a and 2b include, for example,
Use copper foil with a thickness of 150 μm or more. Next, as shown in FIG. 1B, the metal foils 2a, 2
Forming photoresist layers 3a and 3b on b,
It is exposed to light through photomasks 4a and 4b. Next, as shown in FIG. 1C, the unexposed portions are dissolved and removed using a solvent such as chlorocene to form etching resist films 3a and 3b. Next, as shown in FIG. 1D, the metal foils 2a, 2
The portions not covered by the etching resist films 3a and 3b in b are etched away using cupric chloride, etc., and as shown in FIG. The circuit pattern of the inner layer board 6 can be obtained by dissolving and removing the material. Next, as shown in FIG. 1F, outer conductor layers 8a and 8b are laminated on both upper and lower surfaces of the inner layer plate 6 via prepregs 7a, 7b, 7c, and 7d, and then, as shown in FIG. 1G, Bonded with heat using a hot press etc.
A multilayer substrate 9 is formed. Next, as shown in FIG. 1H, through holes 10 are made in the multilayer substrate 9. Next, as shown in FIG. 1I, through-hole plating 1 is formed for electrically connecting between the outer conductor layers 8a and 8b and the inner conductor layers 2a and 2b, each of which has a circuit pattern formed on metal foil.
Apply 2. Next, as shown in FIG. 1J, the outer conductor layer 8
Photosensitive resin layers 3c and 3d are formed on a and 8b and exposed to light through photomasks 4c and 4d. Next, as shown in FIG. 1K, the unexposed portions are dissolved and removed using a solvent such as chlorocene to form etching resist films 3c and 3d. Next, as shown in FIG. 1L, using the etching resist coatings 3c and 3d as masks, the etching resist coating 3 of the outer conductor layer is etched using a cupric chloride solution or the like.
A conventional multilayer printed wiring board 13 is obtained by etching away the portions not covered by layers c and 3d, and then dissolving and removing the etching resist films 3c and 3d with a solvent such as methylene chloride, as shown in FIG. 1M. It will be done. However, the conventional manufacturing method described above has the following major drawbacks when thick metal foil is used for the inner conductor layer. (1) Undercuts due to etching become larger, circuit formation accuracy deteriorates, and etching residue and over-etching are more likely to occur, resulting in insulation deterioration or power supply failure. (2) Because the level difference between the insulating base material of the inner layer plate and the inner conductor layer is large, the level difference portion is not filled with resin during lamination, resulting in lamination voids. (3) Since the inner layer plate has a large step difference, the flatness of the outer conductor layer deteriorates, resulting in poor adhesion of the etching resist film and exposure blur. (Objective of the Invention) The object of the present invention is to eliminate the drawbacks of the conventional multilayer printed wiring, which facilitates power supply, has high circuit formation accuracy, does not generate laminated voids, and has good flatness of the outer conductor layer. The object of the present invention is to provide a method for manufacturing a board. (Structure of the Invention) The method for manufacturing a multilayer printed wiring board of the present invention includes a step of depositing an etching resist film on a desired position of a conductor layer, and using the etching resist film as a mask, desired portions of the conductor layer are formed on the front and back sides. a step of etching from both sides; a step of arranging the etched conductor layers one above the other via a prepreg and bonding them under heat to form an inner layer plate; and applying an insulating resin to the surface of the inner layer plate to form an insulating layer. a step of arranging one or more inner layers on which the insulating layer is formed and an outer conductor layer bonded by thermocompression via a prepreg to form a multilayer board; and a step of forming a through hole in the multilayer board. , a step of applying through-hole plating to the multilayer substrate on which the through-holes have been formed, and forming an etching resist film on a desired position of the outer layer of the multilayer substrate on which the through-hole plating has been applied; The method includes a step of etching away uncovered portions to form an outer layer circuit. (Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIGS. 2A to 2U are cross-sectional views shown in order of steps to explain an embodiment of the present invention. First, as shown in FIG. 2A and B, the metal foil 2
Prepare 2, 22'. The metal foils 22, 22' are copper foils with a thickness of 150 μm or more. Next, as shown in FIG. 2C and D, the metal foil 2
Photoresist 23a, 23 on both sides of 2, 22'
b, 23a', 23b' are deposited and photomask 24 is applied.
a, 24b and 24a', 24b'. Next, as shown in FIG. 2E and F, the unexposed portions are dissolved and removed using a solvent such as chlorocene to form the etching resist coatings 23a, 23b and 23.
form a' and 23b'. Next, as shown in FIG. 2G and H, the metal foil 2
The portions not covered by the etching resist coatings 23a, 23b and 23a', 23b' are etched from both upper and lower surfaces of 2, 22' using cupric chloride solution or the like. Next, as shown in FIGS. 2I and 2J, etching resist coatings 23a, 23b and 23 are formed.
a' and 23b' are removed using a solvent such as methylene chloride. Next, as shown in FIG. 2K, the etched metals 22 and 22' are placed one above the other through the prepreg 27a, and as shown in FIG. Can be formed. Next, as shown in FIG. 2M, insulating resin layers 34a and 34b are formed on the front and back surfaces of the inner layer plate 26 by screen printing, roll coating, etc. to form an insulating resin coated inner layer plate 35. . Next, as shown in FIG. 2N, a second
As shown in Figure O, a multilayer substrate 29 is formed by thermocompression bonding using a hot press. Next, as shown in FIG. 2P, through holes 30 are formed in the multilayer substrate 29 using a conventional method. Next, as shown in FIG. 2Q, the outer conductor layers 28a, 2
Through-hole plating 32 is provided to electrically connect the conductor portions of the inner layer plate 8b and the insulating resin coated inner layer plate 35. Next, as shown in FIG. 2R, the outer conductor layer 28
After forming hot resists 23c and 23d on the surfaces of the through-hole plating formed on a and 28b, they are exposed to light through photomasks 24c and 24d, and as shown in FIG. The etching resist coatings 23c and 23d are formed by dissolving and removing the resists using a solvent such as the like. Next, as shown in FIG. 2T, an etching resist film 2 is formed on the through-hole plating 32.
The portions not covered by 3c and 23d are removed by etching with cupric chloride solution or the like. Next, the etching resist films 23c and 23d are dissolved and removed using a solvent such as methylene chloride to complete a multilayer printed wiring board 33 as shown in FIG. 2U. In order to clarify the effects of the present invention, Tables 1 and 2 show the accuracy measurement results of multilayer printed wiring boards manufactured by the conventional method and the method of the present invention. Table 1 is based on the conventional method, and Table 2 is based on the method of the present invention.

【table】

[Table] As is clear from Tables 1 and 2 above, the average finish value, maximum value, minimum value, and standard deviation values are all significantly improved by the method of the present invention. That is, since the method of the present invention etches both the upper and lower surfaces of a thick metal foil at once, the etching solution flows through the through holes formed by etching.
The inner wall of the through hole is also etched, creating an undercut.
Since the surface is flat with no etching residue or over-etching, the accuracy of circuit formation is improved. In addition, the etched part of the thick metal foil
Since it is filled with insulating resin, there is no level difference between the inner layer plates, and the occurrence of lamination voids can be prevented. Furthermore, the flatness of the multilayer conductor layer is also good, making it possible to form outer layer circuits with high precision. In this example, a four-layer multilayer printed wiring board using one insulating resin coated inner layer board was explained.
Of course, there is no problem in using two or more insulating resin-coated inner plates, or an inner plate formed by a conventional method. (Effects of the Invention) As explained above, according to the present invention, good power supply is possible, circuit formation accuracy is high, stacking voids do not occur, the flatness of the outer conductor layer is good, and patterns can be improved. A multilayer printed wiring board that can be formed with precision is obtained.

[Brief explanation of drawings]

1A to 1M are cross-sectional views shown in the order of steps to explain a conventional method for manufacturing a multilayer printed wiring board;
Figures A to U are cross-sectional views shown in order of steps to explain an embodiment of the present invention. 1...Insulating substrate, 2a, 2b, 22, 22'...
...Metal foil, 3a, 3b, 3c, 3d, 23a, 2
3b, 23a', 23b', 23c, 23d...Photoresist, 4a, 4b, 4c, 4d, 24a, 2
4b, 24a', 24b', 24c, 24d...Photomask, 6, 26...Inner layer plate, 7a, 7b, 7
c, 7d, 27a, 27b, 27c... prepreg, 8a, 8b, 28a, 28b... outer conductor layer, 9, 29... multilayer board, 10, 30... through hole, 12, 32... through hole Plating, 13, 33...Multilayer printed wiring board, 34a, 3
4b... Insulating resin layer, 35... Insulating resin coat inner layer plate.

Claims (1)

[Claims] 1 A step of depositing an etching resist film on a desired position of the conductor layer, a step of etching a desired portion of the conductor layer from both the front and back sides using the etching resist film as a mask, and a step of forming a prepreg on the etched conductor layer. a step of forming an inner layer plate by arranging the inner layer plate one above the other and thermally pressing the inner layer plate, a step of applying an insulating resin to the surface of the inner layer plate to form an insulating layer, and a step of forming the inner layer plate with the insulating layer formed thereon on one or more inner layers. a process of arranging and thermocompression-bonding the multilayer conductor layer via prepreg to form a multilayer board; a process of forming through holes in the multilayer board; and a process of through hole plating in the multilayer board with the through holes formed. a step of depositing an etching resist film at a desired position on the outer layer of the multilayered substrate to which the through-hole plating has been applied, and etching away the portions not covered with the etching resist film to form an outer layer circuit. A method for producing a multilayer printed wiring board, comprising: