JPH05335739A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To liberate and remove stress generated at the time of manufacturing a bonding sheet in order to prevent a size change inside a process at the time of manufacturing a multilayer printed wiring board. CONSTITUTION:Prepreg 2a obtained by performing coating of epoxy resin in an epoxy resin tank 3 and drying thereof in a drying tower 6 on a running glass cloth 2 is supported and fixed by means of two pieces of pinch rollers 9, 10 in its horizontally running part, and heat treatment is performed on the slack part 2a1 formed between them by a far infrared ray furnace 11 so as to liberate and remove stress generated on the prepreg 2a during coating and drying in the molten and semisolidified state of the prepreg 2a in order to perform secondary molding having this prepreg as a bonding sheet.

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.

[0002]

2. Description of the Related Art With increasing speed of electronic equipment, wiring lengths and through-hole intervals are becoming finer. Then, in the production of a multilayer printed wiring board, in order to bond the inner layer circuit boards to each other and the outer conductive layer, a prepreg is interposed between the both to perform secondary molding. The circuit board may expand or contract. This expansion and contraction causes a deviation between the circuit patterns of both the bonding and the deviation, which is a serious problem in the present circumstances where the patterns are becoming finer and the density is higher.

The cause of expansion and contraction of the inner layer circuit board (hereinafter referred to as dimensional change in process) at the time of the secondary molding is that the prepreg is applied and dried because tension is applied to the prepreg. May be under stress. That is, it is considered that the stress exerts an influence on the inner layer circuit board which is in a molten state when pressure is applied during the secondary molding. The inner layer circuit board shrinks in the direction in which the tension is applied during the prepreg coating, and does not shrink much in the other directions.

In order to prevent the dimensional change in the process as described above, the fibers of the glass cloth, which is the base material of the prepreg, are made dense in the direction in which the tension acts during the coating, or the tension acting during the coating is reduced. Therefore, measures such as lowering the coating speed have been adopted.

[0005]

However, even if the above-mentioned preventive means is adopted, not only there is a problem in terms of productivity, suitability for specification of glass cloth, etc., but also the stress is not completely eliminated. It is not a complete solution for in-process dimensional change.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a multilayer printed wiring board which does not cause a dimensional change in the process regardless of the structure of the glass cloth and the method of manufacturing the prepreg. ..

[0007]

A method for manufacturing a multilayer printed wiring board according to the present invention is a multilayer printed wiring board in which an inner layer circuit board having a circuit pattern, a prepreg as a bonding sheet, and an outer conductive layer are integrated. At the time of manufacturing, a step of once melting the prepreg in a state where no tension is applied is characterized.

[0008]

In the method for manufacturing a multilayer printed wiring board of the present invention having the above-mentioned structure, the stress generated in the prepreg during coating and drying of the prepreg is released and removed in the step of once melting the prepreg. In-process dimensional change during molding is prevented.

[0009]

EXAMPLES The present invention is based on the knowledge that, before the interposition between the two to be bonded, the stress in the prepreg can be removed to prevent the dimensional change in the process during the secondary molding. That is, if the prepreg in a semi-cured state is once melted in the state where no external force is acting, the stress generated at the time of prepreg production is released and removed, and this is interposed between the bonding both to perform secondary molding, It is possible to completely prevent the dimensional change in the process.

A normal prepreg has a tension of 20 kgf / m to 60 kgf / m during coating and drying, and if the prepreg manufactured in such a state is used as a bonding sheet for secondary molding, Due to the heating and melting due to the temperature at the time of the subsequent molding, a force for returning to the original acts on the prepreg, causing a dimensional change in the process. Therefore, in the present invention, the above prepreg is melted in a tension of 10 kgf / m or less, preferably 0 to 2 kgf / m, and semi-cured to release and remove the stress generated during the prepreg production. This allows
In-process dimensional changes are minimized.

The inner layer circuit board used in the present invention may be a commonly used inner layer circuit board, and does not require any special one. That is, a double-sided copper clad laminate such as a conventional glass cloth base material epoxy or glass cloth base material polyimide is used.

Any appropriate prepreg can be used as long as it is used for a multilayer printed wiring board, and it is not necessary to prepare a special prepreg.

Further, a metal foil such as a copper foil may be used as the outer conductive layer, but may be formed by an additive method or the like after laminating and molding.

An embodiment of the present invention will be described below with reference to specific examples.

(1) A circuit was formed on a glass cloth base material epoxy resin copper clad laminate (thickness: 0.2 mm), and the surface was subjected to an oxidation treatment to form an inner layer circuit board.

(2) A thermosetting epoxy resin was applied to a 2116 type glass cloth having a thickness of 100 μm. At this time, the tension acting on the prepreg in a semi-cured state was 30 kgf / m.

(3) The prepreg obtained as described above is irradiated with far infrared rays in a state where no tension is applied,
The melting point of 70 ° C. was heated to 90 ° C. to melt. (4) Using the prepreg subjected to the above treatment as a bonding sheet, the inner layer circuit board and the thickness of 18 μm shown in (1) are used.
Combined with the outer layer copper foil, sandwiched between SUS plates, 30kg
Secondary molding is performed under the conditions of f / cm ² and 170 ° C. × 2 hr.
A multilayer copper clad laminate was obtained. The structure is a four-layer plate with two prepregs on each side.

In order to compare with the above embodiment, the above (1)-
The multilayer copper clad laminate was constructed by omitting the step (3) in the step (4). This is Comparative Example 1.

Further, the coating conditions in the step (2) of the steps (1) to (4) are changed so that the tension is 10 kgf / m, and the step (3) is omitted. A multilayer copper clad laminate was constructed. This is Comparative Example 2.

The following table shows a comparison of the pattern shrinkage rates in the secondary molding of the above-mentioned examples of the present invention and the above-mentioned respective comparative examples.

[0021]

[Table 1] From the above table, it can be seen that the manufacturing method of the present invention can minimize the dimensional change in the process.

FIG. 1 shows an example of a manufacturing apparatus for carrying out the above embodiment of the present invention. In this figure, the glass cloth 2 drawn out from the glass cloth roll 1 passes through a guide roll 4 in the upper front side of the epoxy resin tank 3 and a guide roll 5 in the epoxy resin tank 3, and after the epoxy resin is coated. The prepreg 2a advances into the drying tower 6, is folded back by the upper guide roll 7, passes through the drying tower 6, and the epoxy resin is dried during this time. Then, the prepreg 2a is guided by a guide roll 8 provided below the drying tower 6 to turn its traveling direction to a horizontal direction.

Two pinch rollers 9 and 10 are provided in the horizontal running portion of the prepreg 2a with a certain space therebetween, and the prepreg 2a has a slack portion between the pinch rollers 9 and 10. 2a1 is formed, and the slack portion 2a1 is heat-treated by the far-infrared furnace 11. The prepreg 2 a that has passed through the far-infrared furnace 11 is wound around the prepreg roll 12.

In the manufacturing apparatus having the above construction, the prepreg 2a is held by the pinch rollers 9 and 10 before and after the far-infrared furnace 11, and the slack portion 2a1 is formed between these pinch rollers, so that the prepreg 2a1 is formed. The tension associated with the feeding of 2a is blocked between the pinch rollers 9 and 10. That is, the epoxy resin is applied in the epoxy resin tank 3 and the drying tower 6
Since the prepreg 2a obtained by drying the prepreg 2a is once heated and melted and semi-cured by the far-infrared furnace 11 in a state where no tension acts, the prepreg 2a is coated and dried under the action of tension.
The stress that had been generated in is released and removed. This manufacturing apparatus carries out the step (3).

The manufacturing apparatus shown in FIG. 1 carries out coating, drying and stress removal as a series of continuous operations. When the drying tower 6 is exited, the prepreg 2a is cut into a required size. , If this cut product is properly supported on a gantry and subjected to the same heat treatment as in the above device, melting and semi-curing can be realized in the state where no tension acts, and stress generated in the previous step Can be opened and removed.

[0026]

As is apparent from the above, in the method for manufacturing a multilayer printed wiring board according to the present invention, the stress generated during the coating and drying of the prepreg which serves as the bonding sheet during the secondary molding is released and removed. Therefore, it is possible to minimize the deviation of the circuit pattern at the time of the secondary molding, and it is possible to manufacture the miniaturized and high-density multilayer printed wiring board with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing apparatus for carrying out a manufacturing method of the present invention.

[Explanation of symbols]

1 ... Glass cloth roll, 2 ... Glass cloth, 2a
... prepreg, 3 ... epoxy resin tank, 4, 5, 7,
8 ... Guide roll, 6 ... Drying tower, 11 ... Far infrared furnace, 9, 10 ... Pinch roller, 12 ... Prepreg roll.

Claims (1)

[Claims] 1. An inner layer circuit board on which a circuit pattern is formed,
When manufacturing a multilayer printed wiring board by integrating a prepreg as a bonding sheet and an outer conductive layer,
A method for manufacturing a multilayer printed wiring board, characterized in that a step of temporarily melting the prepreg in a state where no tension is applied is performed.