JP2002299819A - Method of manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer printed wiring board, restraining prepreg molten resin from flowing out from the periphery of the board in a lamination process, and making the board uniform in thickness. SOLUTION: Latticed or island-shaped resin patterns 4a and 4b of thermosetting resin or ultraviolet-curing resin are previously printed on the surfaces of inner circuits 2a and 2b of wiring boards 10 and 20 arranged on both the sides of a prepreg 5, getting gradually higher in pattern density from the centers to peripheries of the boards and then cured for the formation of a multilayer printed wiring board. The re-melted resin of the prepreg 5 is more restrained from flowing around the center than around the periphery of the board by the resin patterns 4a and 4b, so that an insulating layer 6 gets uniform in thickness from the center to periphery of the board, and the multilayer printed wiring board is improved in thickness uniformity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board capable of improving the uniformity of the interlayer thickness of an inner insulating layer in order to improve the accuracy of characteristic impedance. About.

[0002]

2. Description of the Related Art Generally, multilayer printed wiring boards are used in electronic devices such as computers that require high-speed signal processing. For a multilayer printed wiring board used in such an electronic device, the reliability of the circuit and its dimensional accuracy are particularly strictly required. Therefore, it is necessary to uniformly adjust the characteristic impedance, that is, the thickness of the insulating layer. There is.

[0003] A multilayer printed wiring board is generally manufactured by laminating an outer layer substrate by a heat and pressure press via a prepreg (adhesive sheet) on an inner layer substrate on which a circuit is formed, but the thickness varies. It was known. The first reason is that the resin contained in the prepreg between the substrates when heated by the press flows out due to the pressing force of the press (several tens of kg / cm ² ), and the resin between the substrates at the peripheral portion of the substrate decreases. It is. The second reason is that the pressing pressure is affected by the location depending on the circuit density of the substrate in the inner layer, and the amount of resin between the substrates varies.

[0004]

As a technique for suppressing a decrease in the amount of resin around a substrate and making the thickness uniform, Japanese Patent Application Laid-Open No.
No. 148737 discloses that a resin pattern is printed on a peripheral portion of a substrate outside a manufacturing area, or a metal pattern is formed to suppress the flow of resin to the outside of the substrate to make the thickness of the substrate uniform. There is disclosed a method for converting the data. Japanese Patent Application Laid-Open No. 5-121876 discloses that a temperature gradient is provided when heating and pressurizing treatment is performed by a press so that the amount of resin flow in the central portion of the substrate is the largest, and the resin gradually flows toward the peripheral portion. Techniques for reducing the amount of flow have been disclosed.

[0005] As a technique for improving the thickness variation due to the influence of the circuit pattern existing on the inner layer board, Japanese Patent Publication No. 3-65910 and the like disclose a technique between a circuit on the inner layer board surface and a step between the board surface. A technique of embedding a resin, performing a surface smoothing process, and laminating an outer layer substrate on the inner layer substrate via a prepreg is disclosed. Also, JP-A-11-233
No. 938 discloses that a resin is printed between conductive circuits on an inner layer substrate, a resin is also printed on the conductive circuits in a dot shape, and a film-like semi-cured resin is adhered thereon in an uncured state. A technique for reducing variations in plate thickness due to circuit density of a substrate has been disclosed.

Although these techniques have achieved a certain effect in making the thickness of the insulating layer of the multilayer printed wiring board uniform, special processing condition control is required, the process becomes complicated, and the manufacturing cost increases. Was causing it.

Accordingly, it is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a manufacturing method in which the thickness of an insulating layer of a multilayer printed wiring board can be easily controlled.

[0008]

A method of manufacturing a multilayer printed wiring board according to the present invention comprises a step of manufacturing a multilayer wiring board by superposing a prepreg and a conductor layer substrate on a wiring board and heating and pressing the prepreg. Before heating and pressurizing on at least one substrate surface on both sides of the substrate, a lattice-shaped or island-shaped resin pattern is printed in advance so that the pattern density increases from the center to the periphery of the substrate, and the resin pattern is formed. It is characterized by being cured.

The substrate surface areas defined by the resin pattern formed in the lattice pattern are connected by openings provided in the resin pattern. The width of the resin pattern in the length direction of the opening is formed so as to decrease from the center of the substrate to the periphery, and the flow of the re-melted resin of the prepreg during the heating and pressing is controlled to decrease toward the periphery of the substrate. Is done.

A thermosetting resin or an ultraviolet curable resin is used as the resin for forming the resin pattern. Preferably, the resin pattern is formed to be thicker from the center to the periphery of the substrate.

[0011] The substrate on both sides of the prepreg has a conductive circuit on the bonding surface of the prepreg, and an insulating layer is filled in advance and the surface of the substrate is flattened before the heating and pressing between the conductive circuits. You can also. In this case, since a thin prepreg can be used, the thickness of the multilayer printed wiring board can be reduced.

[0012]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a main part of a substrate for explaining steps of a method of manufacturing a multilayer printed wiring board according to a first embodiment of the present invention, and FIG. 2 is a continuation of FIG. It is sectional drawing of the principal part of a board | substrate for demonstrating a process. Here, a case in which a four-layer multilayer printed wiring board is manufactured will be described.

First, as shown in FIG. 1A, an inner layer circuit 2a is formed by patterning a copper foil on one side of an insulating substrate 1a having copper foils on both sides by photolithography, thereby manufacturing a wiring board 10. . Copper foil not etched is outer layer copper foil 3a
Becomes In addition, as the insulating substrate 1a, an epoxy resin substrate reinforced with glass fiber, a polyimide resin substrate, or a substrate of a polyimide resin modified with an epoxy resin can be used, but is not limited thereto.

Next, as shown in FIG. 1B, a resin pattern 4a is printed on the inner layer circuit 2a by a screen printing method and cured. As a material of the resin pattern 4a, a thermosetting or ultraviolet curable resin ink based on an epoxy resin can be used. The thickness and area of the resin pattern 4a are determined by the amount of resin in the prepreg (determining the thickness of the interlayer insulating layer after lamination with an adhesive sheet when the insulating substrate is laminated) and the thickness of the interlayer insulating layer of the multilayer printed wiring board. Determined by design values. The thickness of the resin pattern 4a is controlled by controlling the viscosity of the ink, the amount of the resin, the printing pressure, and the like.

It is important that the resin pattern 4 is adjusted so that the thickness at the periphery and the center of the substrate at the time of lamination is corrected.
That is, the resin pattern 4a is formed by printing such that the density of “a” becomes larger toward the periphery. The regions partitioned by the resin pattern 4a are connected so that the flow of the prepreg during lamination can be appropriately controlled.

FIG. 3 is a plan view showing an example of the resin pattern 4a. In FIG. 3, the resin pattern 4a has a pattern shape in which openings are formed in a lattice pattern and regions partitioned by the lattice pattern are connected, and the density of the pattern increases toward the periphery, and the width of the opening increases. Is characterized in that it becomes narrower toward the periphery. In addition, the resin pattern 4a may be formed in an island shape, and the density thereof may be increased toward the periphery. By forming the resin pattern 4a in such a shape, the flow of the prepreg during lamination can be controlled to be smaller toward the periphery.

It is desirable that the thickness of the resin pattern 4a be increased toward the periphery. By increasing the thickness of the resin pattern 4a toward the periphery, the difference in plate thickness between the central portion and the peripheral portion after lamination can be further reduced.

As a method of forming the resin pattern 4a to be thicker toward the periphery, the following method can be used. (1) A UV-curable resin is applied to the entire inner circuit layer, and the UV-curable resin is exposed to ultraviolet rays using a mask having a higher transmittance of ultraviolet rays toward the edge of the board, and is developed. The degree of curing of the resin is higher at the end of the substrate, and the thickness of the resin can be increased at the end of the substrate. (2) As shown in FIG. 6, a thermosetting resin is applied to the inner layer circuit 2c.
Print the entire surface in an island or grid pattern and semi-cur. Next, the height of the resin upper surface is formed on the concave surface by pressing and pressing the end plate 70 having a convex spherical surface on the resin of the substrate. Next, the resin is fully cured to form a resin pattern 4e that is thicker toward the plate edge. In FIG. 6, reference numeral 1c denotes an insulating substrate, and 3c denotes an outer copper foil.

Next, a wiring board 20 having an inner layer circuit 2b on an insulating substrate 1b is prepared by the same process as that for manufacturing the wiring board 10, and both boards are placed on both sides of the prepreg 5 as shown in FIG. After the disposition, as shown in FIG. 1D, the prepreg 5 is melted by heating and pressing with a lamination press, and the two substrates are adhered to each other with the prepreg 5, thereby manufacturing the shield plate 30.
In the drawing, reference numeral 6 denotes an insulating layer in which the resin in a semi-cured state in the prepreg 5 is re-melted and cured, and reference numeral 3b denotes an outer copper foil.

Next, as shown in FIG.
After forming the through hole 11 by drilling to 0, FIG.
As shown in (b), a copper plating film 12 is formed on the entire surface of the shield plate including the through holes by electroless copper plating and electrolytic copper plating.

Next, the copper plating film 12 is patterned by a photolithography method, as shown in FIG.
The multilayer printed wiring board 40 in which the through holes 13 and the outer layer circuits 14 are formed and the interlayer thickness is maintained uniform is manufactured.

In the method for manufacturing a multilayer printed wiring board according to the present embodiment, the resin patterns 4a and 4b suppress the flow of the molten resin of the prepreg toward the periphery of the substrate during lamination. This has the effect of reducing the difference in thickness between layers between the central part and the central part.

In the first embodiment of the present invention, the resin pattern is formed on both the inner layer circuits of the substrates to be laminated. However, the resin pattern may be formed only on the inner layer circuit surface of one of the substrates.

Next, a second embodiment of the method for manufacturing a multilayer printed wiring board according to the present invention will be described with reference to the drawings.

FIG. 4 is a sectional view of a main part of a substrate for explaining steps of a method of manufacturing a multilayer printed wiring board according to a second embodiment of the present invention, and FIG. 5 is continued from FIG. It is sectional drawing of the principal part of a board | substrate for demonstrating a process. Here, a case in which a four-layer multilayer printed wiring board is manufactured will be described.
In the drawings, the same reference numerals in FIGS. 1 and 2 denote the same components. In the present embodiment, the space between the inner layer circuits is filled with an insulating layer in advance, and the substrate surface is flattened. The present embodiment is effective when a thin multilayer printed wiring board is manufactured because a multilayer printed wiring board having a uniform thickness can be obtained using a thin prepreg.

First, as in the first embodiment,
An inner layer circuit 2a is formed by patterning the copper foil on one side of the insulating substrate 1a having copper foils on both sides by photolithography, and the wiring board 10 is manufactured (FIG. 4A). The copper foil that is not etched becomes the outer layer copper foil 3a. Next, the insulating layer 15 is screen-printed between the inner layer circuits 2a to flatten the substrate surface (FIG. 4B).

As the material of the insulating layer 15, an epoxy resin or a polyimide resin based ultraviolet curable resin or a thermosetting resin is usually used, but a thermoplastic resin can also be used. As the thermoplastic resin, resins such as polycarbonate, polyarylate, polyamide, polyamideimide, polyesterimide, polyphenylene ether, and polytetrafluoroethylene can be used. Solvents for dissolving these resins can be appropriately selected. Usually, as the material of the insulating layer 15, a material similar to the material type of the insulating substrates 1a and 1b is selected and used, but the material type of the insulating layer 15 is the material type of the insulating substrates 1a and 1b. And may be different. For example, when epoxy resin substrates are used as the insulating substrates 1a and 1b, an epoxy resin is usually used as a material of the insulating layer 15, but a resin having a smaller dielectric constant and / or a lower dielectric tangent than the epoxy resin is used instead of the epoxy resin. Can be used. Examples of this include resins such as the above-mentioned polyimide, bismaleimide triazine resin, polyphenylene ether, and polytetrafluoroethylene. These resins have a smaller dielectric constant and a lower dielectric loss tangent than epoxy resins, and the transmission of the inner layer circuits 2a and 2b. This has the effect of improving the characteristics and high frequency characteristics.

Next, as shown in FIG. 4C, a resin pattern 4c is printed on the inner circuit 2a by a screen printing method and cured. As the material of the resin pattern 4c, an epoxy resin-based thermosetting or ultraviolet curable resin ink can be used as in the first embodiment. The thickness and area of the resin pattern 4c are determined by the amount of resin in the prepreg and the design value of the thickness of the interlayer insulating layer of the multilayer printed wiring board as in the first embodiment. The thickness of the resin pattern 4c is controlled by controlling the viscosity of the ink, the amount of the resin, the printing pressure, and the like.

The resin pattern 4c is formed by printing so that the density of the resin pattern 4c increases toward the periphery so as to correct the thickness at the periphery and the center of the substrate at the time of lamination.

The resin pattern 4c is formed in the form of a lattice or dots, as in the first embodiment. When the resin pattern 4c is formed in a lattice shape, openings are provided in the resin pattern 4c as in FIG. 3 to connect the regions partitioned by the resin pattern 4c so that the flow of the prepreg during lamination can be appropriately controlled. I do.

It is desirable that the thickness of the resin pattern 4c be increased toward the periphery, and the same method as in the first embodiment can be used.

Next, a wiring board 20 having an inner layer circuit 2b on an insulating substrate 1b is prepared by a process similar to the above-described manufacturing process of the wiring board 10, and both sides of the prepreg 5 are provided as shown in FIG. After arranging the substrates, as shown in FIG. 4E, the prepreg 5 is melted by heating and pressing with a laminating press, and the two substrates are adhered to each other with the prepreg 5, and the shield plate 50 is manufactured. In the drawing, reference numeral 6a denotes an insulating layer in which the semi-cured resin in the prepreg 5 is re-melted and cured, and reference numeral 4d
Indicates a resin pattern.

Next, as shown in FIG.
After forming the through hole 11a by drilling to 0, FIG.
As shown in (b), a copper plating film 12a is formed on the entire surface of the shield plate including the through holes by electroless copper plating and electrolytic copper plating.

Next, the copper plating film 12a is patterned by photolithography to form a through hole 13a and an outer layer circuit 14a as shown in FIG. Is manufactured.

In the method of manufacturing a multilayer printed wiring board according to the present embodiment, the interlayer insulating layer of the multilayer printed wiring board is formed using a thin prepreg in order to fill the inner layer circuits in advance with the insulating layer 15 and flatten the surface of the substrate. Has the effect of reducing variations in thickness. In the above-described second embodiment of the present invention, the resin pattern is formed on both the inner layer circuits of the substrates to be laminated, but may be formed only on the inner layer circuit surface of one of the substrates.

In the above-described embodiment of the present invention, 4
Although the laminated plate has been described, it goes without saying that the present invention can be applied to a method for producing a multilayered plate having more than four layers. Also,
It goes without saying that the present invention is also applicable to a method for manufacturing a multilayer printed wiring board in which a single-sided or double-sided wiring board is laminated via prepregs on both sides of a wiring board having circuits formed on both sides.

[0038]

As described above, in the method of manufacturing a multilayer printed wiring board according to the present invention, a grid-like resin pattern having dots or openings in advance on the inner circuit surface of the adhesive surface of the prepreg is provided around the substrate. The following effect can be obtained by forming the pattern density as high as possible. (1) Since the flow of the remelted prepreg during lamination can be reduced toward the periphery of the substrate, the difference in the thickness of the insulating layer between the periphery of the substrate and the center of the substrate can be reduced, and the uniformity of the thickness of the multilayer printed wiring board can be reduced. Is improved. As a result, the accuracy of the characteristic impedance of the multilayer printed wiring board is improved. (2) In particular, by forming the resin pattern thicker toward the periphery of the substrate, the thickness uniformity of the multilayer printed wiring board can be further improved. (3) In order to improve the uniformity of the thickness by using a thin prepreg material in combination with the method of pre-coating and flattening the resin between the inner layer circuits (gap), a thin multi-layer with a small thickness variation is used. Manufacture of printed wiring boards.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a substrate for describing steps of a method for manufacturing a multilayer printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a substantial part of the substrate for explaining a step following the step shown in FIG. 1D of the method for manufacturing the multilayer printed wiring board according to the first embodiment of the present invention;

FIG. 3 is a plan view illustrating an example of a resin pattern in the method for manufacturing the multilayer printed wiring board according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main part of a substrate for describing steps of a method for manufacturing a multilayer printed wiring board according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a substantial part of the substrate for explaining a step following the step shown in FIG. 4E of the method for manufacturing the multilayer printed wiring board according to the second embodiment of the present invention;

FIG. 6 is a cross-sectional view of a main part of the substrate for describing a method of forming a resin pattern in the method of manufacturing a multilayer printed wiring board according to the present invention.

[Explanation of symbols]

 1a, 1b, 1c Insulating substrate 2a, 2b, 2c Inner layer circuit 3a, 3b, 3c Outer layer copper foil 4a, 4b, 4c, 4d, 4e Resin pattern 5 Prepreg 6, 6a, 15 Insulating layer 30, 50 Shield plate 10, 20 Wiring board 11, 11a Through hole 12, 12a Copper plating film 13, 13a Through hole 14, 14a Outer circuit 40, 60 Multilayer printed wiring board 70 End plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E346 AA12 AA38 CC08 CC09 CC10 CC32 DD02 DD03 DD12 EE09 FF15 GG15 HH02 HH24

Claims (11)

[Claims] 1. A step of manufacturing a multilayer wiring board by superposing a prepreg and a conductor layer substrate on a wiring board and heating and pressurizing the circuit board, wherein at least one substrate surface on both sides of the prepreg is heated and pressurized before the heating and pressurization. A method of manufacturing a multilayer printed wiring board, wherein a lattice-shaped or island-shaped resin pattern is printed in advance so that the pattern density increases from the center of the substrate toward the periphery, and the resin pattern is cured. 2. The resin pattern is formed such that the substrate surface region defined by the resin pattern formed in the lattice shape is connected by an opening provided in the resin pattern. The method for producing a multilayer printed wiring board according to claim 1. 3. The method for manufacturing a multilayer printed wiring board according to claim 2, wherein the width of the opening in the length direction of the resin pattern is reduced from the center of the substrate toward the periphery. 4. The method for producing a multilayer printed wiring board according to claim 1, wherein a thermosetting resin or an ultraviolet curable resin is used as a resin for forming the resin pattern. 5. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said resin pattern is formed to be thicker from a central portion to a periphery of said substrate. 6. In the step of printing the resin pattern, the resin pattern is printed such that the pitch between the shapes of the resin pattern is reduced, and the density of the resin pattern increases from the center to the periphery of the substrate. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the control is performed so as to be as follows. 7. After printing the resin pattern on the substrate using a thermosetting resin, the thermosetting resin is semi-cured, and then a mirror plate having a convex spherical surface is formed on the resin. 6. The method for manufacturing a multilayer printed wiring board according to claim 5, wherein the thickness of the resin pattern is increased from the center to the periphery of the substrate by pressing and pressing. 8. After applying an ultraviolet-curable resin on the substrate, the ultraviolet-curable resin is exposed using a mask having a higher transmittance of ultraviolet rays from the center of the substrate toward the periphery, and then developed. 6. The method for manufacturing a multilayer printed wiring board according to claim 5, wherein the resin pattern is formed to be thicker from the center to the periphery of the substrate. 9. The substrate on both sides of the prepreg has a conductive circuit on an adhesive surface of the prepreg, and the space between the conductive circuits is filled with an insulating layer before the heating and pressurizing, and the surface of the substrate is planarized. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein: 10. The method according to claim 9, wherein the insulating layer is formed of a thermosetting resin, an ultraviolet curable resin, or a thermosetting resin. 11. The method according to claim 9, wherein a value of a dielectric constant and / or a dielectric loss tangent of the insulating layer is smaller than that of the substrate.