JPH1013024A - Method for manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a multilayer printed wiring board for manufacturing a printed wiring board with a high board-thickness accuracy easily. SOLUTION: A mirror plate 8 used when manufacturing a printed wiring board is directly heated by high-frequency induction heating using a heating coil 16, and the prepreg of a lamination body 7 is heated and melted with the heat. In this case, since the mirror plate 8 is located extremely near the lamination body 7, generation of time delay due to heat conduction is small, an optimum temperature profile for melting and curing the prepreg can be obtained in all multilayer printed wiring boards, thus obtaining a multilayer printed wiring board with a high board-thickness accuracy.

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 printed wiring board, and more particularly to a method for manufacturing a printed wiring board for an inner layer and a multilayer printed wiring board, or a printed wiring board for an inner layer and a metal foil using a thermosetting resin or a thermoplastic resin. The present invention relates to a method for manufacturing a multilayer printed wiring board in which layers are formed via a prepreg formed and heated and pressed to form a multilayer.

[0002]

2. Description of the Related Art In recent years, the variety of electronic devices has been reduced, and with the advancement of functions, the external size of electronic components has been reduced, and the electronic components have been mounted and held to connect the components. The density of printed wiring boards is increasing. In particular, multilayer printed wiring boards have been increasingly used as a method for increasing the density of printed wiring boards. Among the general methods for manufacturing a multilayer printed wiring board, a method for forming a multilayer printed wiring board for an inner layer will be described with reference to FIGS. 6 (a) to 6 (f), FIG. 7 and FIG. As shown in FIGS. 6A and 6B, a double-sided copper-clad laminate 3 in which conductive foils 2 are formed on both sides of an insulating plate 1 made of, for example, a glass fiber reinforced epoxy plate is used. Unnecessary portions are removed with an etchant that corrodes and dissolves the substrate, thereby producing an inner-layer printed wiring board 5 on which the conductor circuits 4 are formed as shown in FIGS. 6C and 6D. As shown in FIG. 6 (e), for example, a prepreg 6 made by impregnating a glass cloth with an uncured epoxy resin which is a thermosetting resin, for example, between each layer of the copper foil 2 and the printed wiring board 5 for the inner layer. Are sandwiched to form a laminate 7. Next, FIG.
As shown in FIG. 8, a plurality of laminated bodies 7 are stacked, a head plate 8 is sandwiched between upper and lower parts and between them, and a laminating jig 9 is placed on the upper and lower sides to form a book 10 as shown in FIG. For example, the book 10 is inserted between a hot plate 11 controlled and heated by an electric heater, and is pressurized and controlled by a pressure transmitting plate 12 from above and below, and the prepreg 6 is heated and melted, and each inner layer printed wiring board is The copper foil is bonded to form a multilayer printed wiring board 13 as shown in FIG.

(1) Here, as a known example of a method for manufacturing a multilayer printed wiring board, an example described in Japanese Utility Model Laid-Open No. 58-178596 will be described. As shown in FIG. 10 (a), a method for manufacturing this multilayer printed board is such that a metal 14 to be welded to a prepreg 6 is sandwiched between two printed wiring boards 5 for inner layers having holes for alignment, and a positioning jig is used. When the metal 14 is heated and welded by induction heating with the heating coil 16 for generating high frequency being brought close to the welded portion after setting to 15, FIG.
A four-layer printed wiring board 17 in which two aligned printed wiring boards for inner layers are temporarily fixed as shown in FIG. Next, the temporarily fixed four-layer printed wiring board 17 is removed from the positioning jig 15, and the prepreg 6 and the copper foil 2 are vertically stacked and heated and pressed as shown in FIG. As a result, a multilayer printed wiring board 13 having six layers as shown in d) is obtained.

(2) As a known example of a heating method, an example described in JP-A-5-31808 will be described. The example described in this publication is a method for manufacturing a plastic bonded product, in which a conductive layer is integrally formed on a bonding surface, and this is applied to an electromagnetic induction heating type bonding apparatus having a high-frequency oscillator and a heating coil for generating a magnetic field. This is a method of heating and joining the conductive layers.

[0005]

However, in the prior art, as shown in FIGS. 7 and 8, a book 10 in which a plurality of laminated bodies 7 are superimposed on a head plate 8 and a laminating jig 9 is placed on a hot plate only from the vertical direction. The laminate 7 close to the hot plate 11 for heating by 11
9 is close to the heating profile of the hot plate as shown in FIG. 9, but in the laminated plate in the central portion of the superposition far from the hot plate, a time delay occurs in the heating profile and the curing condition of the prepreg changes, The processing conditions in the subsequent steps due to the worsening of the thickness variation of each multilayer printed wiring board, the worsening of the thickness variation within a single multilayer printed wiring board, and the worsening of the variation of the degree of curing of the prepreg (for example, Due to restrictions on drilling conditions), the characteristics of the printed wiring board are deteriorated, the yield is reduced, and the productivity is reduced. Further, in the conventional example (1), there is no description about a heating method for curing the prepreg in the above problem, and no improvement is made on this point. In the method of the known example (2), since the conductive layer is formed directly on the bonding surface, that is, on the prepreg, the conductive layer interferes with the circuit of another inner-layer printed wiring board, and functions as a multilayer printed wiring board. become unable.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the variation in the thickness of each multilayer printed wiring board, the variation in the thickness of a single multilayer printed wiring board, and the prepreg. To provide a method for manufacturing a printed wiring board that does not deteriorate the characteristics of the prepreg wiring board, reduce the yield, or reduce the productivity due to the restriction of the processing conditions in the subsequent steps due to the deterioration in the degree of curing. is there.

[0007]

According to the present invention, at least one printed circuit board for an inner layer having conductive circuits formed on both sides or a printed circuit board for an inner layer having a conductive circuit on one side is formed by two conductors. The foil or the printed wiring board for the inner layer is disposed outside, and a prepreg is interposed between each metal foil and the printed wiring board for the inner layer, sandwiched by a pair of end plates, one or more of which are stacked, and between the pressure transmitting plates. A method of manufacturing a multilayer printed wiring board having a manufacturing step of a multilayer printed wiring board having a step of forming a multilayer by sandwiching, heating and pressing, comprising a step of directly heating the head plate by high frequency induction heating to form a multilayer. I do.

Here, whether the end plate is made of metal,
A structure in which a plurality of metals are bonded, a structure in which one or more types of metal and one or more types of insulators are bonded, or a structure in which a plurality of metals are bonded by partially changing the arrangement ratio of metals in the thickness direction; It has a structure in which more than one kind of metal and one or more kinds of insulators are attached.

According to the present invention, end plates are provided on both sides of the laminate. The head plate is directly heated by eddy currents and hysteresis loss induced from high frequency, and the heat generated in the head plate is transmitted to the laminate by conduction, and the laminate is heated. As described above, since the heat generating portion is located very close to the laminate, a temperature rising profile with a very small time delay in heat conduction can be obtained. Further, since the magnetic flux penetrating the head plate is uniform at any position, when the thickness of the head plate is constant, the eddy current and the hysteresis loss generated in each head plate are the same, and the heat generation amount is equal for each head plate. For this reason, the same heating profile can be obtained regardless of the position above and below the book.
The curing conditions of the prepreg are the same, and the variation in the thickness of the multilayer printed wiring board and the variation in the degree of curing of the resin are reduced.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1 (a) to 1 (f) and 2 are sectional views showing steps of a method for manufacturing a multilayer printed wiring board according to first to third embodiments of the present invention, and FIGS. FIG. 3 (a) is a perspective view of a metal end plate used in the method of manufacturing the printed wiring board according to the first embodiment shown in FIG. 1, and FIG. 4 is a temperature profile of a laminate for explaining a printed wiring board according to the embodiment. First, the method for manufacturing a printed wiring board according to the first embodiment of the present invention has a size of 200 × 200 mm, a conductive foil thickness of 35 μm, and a base material thickness of 200 μm as shown in FIGS. 1 (a) and 1 (b).
After forming a circuit etching mask with a dry film etching resist on the double-sided copper-clad laminate 3 of m, etching was performed with an aqueous ferric chloride solution, and then the etching mask was peeled off. Thus, the printed wiring board 5 for the inner layer having the conductor circuit 4 as shown in FIGS. 1C and 1D was obtained. The printed wiring board 5 for the inner layer, the prepreg 6 and the copper foil 2 were stacked to obtain a laminate 7 as shown in FIG. As shown in FIG. 3 (a), fifty of the laminated bodies 7 and 51 of pure copper end plates 8 of 200 × 200 mm in size and 1.2 mm in thickness as shown in FIG. As shown in (1), it was set between the pressure transmitting plates 12 and set so that the magnetic flux generated by the coils inside the high-frequency induction heating coil 16 and the plane portion of the end plate 8 were perpendicular to each other. A high-frequency current having a frequency of 150 KHz was applied to the heating coil 16 under the following conditions: 0 to 25 minutes: 70 KW, 25 to 50 minutes: 35 KW, 50 to 110 minutes: 10 KW. At this time, the temperature rise profile of the internal laminated body 7 was obtained in the vicinity of the pressure transmitting plate 12 and at the center of the stack as shown in FIG. In this heating profile, a maximum temperature difference of 3 ° C. occurred at the same time. This was １ ／ of the temperature difference of 15 ° C. during lamination using the conventional hot plate. Then, a multilayer printed wiring board 13 as shown in FIG. 1 (f) was obtained. The thickness of the multilayer printed wiring board had a variation of 3% of the total thickness, but this was half of the variation of 6% of the thickness of the conventional multilayer printed wiring board.

FIG. 3B is a perspective view of a mirror plate used in a method for manufacturing a printed wiring board according to a second embodiment of the present invention. The method for manufacturing a printed wiring board according to the second embodiment of the present invention is performed using a mirror plate 8 shown in FIG. End plate 8
Has a size of 200 × 200 m as shown in FIG.
m, a thickness of 0.1 mm on both sides of a pure copper plate 18 having a thickness of 1.2 mm.
mm stainless steel SUS316L19 is attached. First, as shown in FIGS. 1A to 1E, a printed wiring board 5 for an inner layer was prepared, and a prepreg 6 and a copper foil 2 were stacked to form a laminate 7. As shown in FIG. 2, 50 of the laminates 7 and the head plates 8 and 51 of FIG. 3B are alternately stacked and placed between the pressure transmitting plates 12, and the coil is placed inside the high-frequency induction heating coil 16. The resulting magnetic flux was set to be perpendicular to the plane portion of the mirror plate 8. A high-frequency current having a frequency of 150 KHz was applied to the heating coil 16 under the following conditions: 0 to 25 minutes: 70 KW, 25 to 50 minutes: 35 KW, 50 to 110 minutes: 10 KW. Also at this time, as for the temperature rise profile of the internal laminated body 7, the temperature rise profile as shown in FIG. In this heating profile, a maximum temperature difference of 3 ° C. occurred at the same time. This was １ ／ of the temperature difference of 15 ° C. during lamination using the conventional hot plate. Then, a multilayer printed wiring board 13 as shown in FIG. 1 (f) was obtained. The thickness of the multilayer printed wiring board had a variation of 3% of the total thickness, but this was half of the variation of 6% of the thickness of the conventional multilayer printed wiring board. Since the surface hardness of the end plate 8 is two to three times that of pure copper, the end plate 8 is hardly damaged. When the pure copper end plate 8 of the first embodiment is used three times, it cannot be used due to scratches and deformation. On the other hand, there was no scratch or deformation even after use 1000 times. The amount of heat generated by the stainless steel portion was 0.4%, which was not different from that of the pure copper end plate 8, and that there was no difference in the temperature profile. The mirror plate 8 used in this embodiment was coated with a 0.04 mm-thick fluororesin, and the same result was obtained. By this fluororesin coating, the resin does not adhere to the prepreg, and it becomes unnecessary to perform polishing or the like for removing the resin.

FIG. 3C is a perspective view of a mirror plate used in a method of manufacturing a printed wiring board according to a third embodiment of the present invention. The method for manufacturing a printed wiring board according to the third embodiment of the present invention is performed using a mirror plate 8 shown in FIG. End plate 8
Has a size of 200 × 200 m as shown in FIG.
m, thickness of center 1.19 mm, thickness of periphery 1.24
mm, the ratio of the length of the central part to the peripheral part is 4: 1, and the pure copper plate 18 made to have the same sectional area as that of FIG.
A convex stainless steel SUS316L19 is attached to both sides of the substrate so that the total plate thickness becomes 1.4 mm. First, as shown in FIGS. 1A to 1E, a printed wiring board 5 for an inner layer was prepared, and a prepreg 6 and a copper foil 2 were stacked to form a laminate 7. As shown in FIG. 2, 50 laminated bodies 7 and the end plates 8 and 51 shown in FIG.
Was set so that the magnetic flux generated by the coil and the plane portion of the end plate 8 were perpendicular to each other. A high-frequency current having a frequency of 150 KHz was applied to the heating coil 16 under the following conditions: 0 to 25 minutes: 73 KW, 25 to 50 minutes: 40 KW, 50 to 110 minutes: 18 KW. At this time, the temperature rise profile of the internal laminated body 7 was obtained in the vicinity of the pressure transmitting plate 12 and at the center of the stack as shown in FIG. In this heating profile, a maximum temperature difference of 3 ° C. occurred at the same time. This was １ ／ of the temperature difference of 15 ° C. during lamination using the conventional hot plate. When the temperature distribution in the cross section direction of the head plate 8 was measured, as shown in FIG. 5, the temperature difference between the center part and the peripheral part of the head plate 8 was about 3 ° C. in the second embodiment. It was within ° C. This is to make the temperature distribution of the head plate 8 more uniform by compensating for the heat that escapes from the periphery of the head plate 8 to the outside by increasing the calorific value by increasing the thickness of the pure copper plate 8 of the head plate 8 at the periphery. It is because was made. Then, a multilayer printed wiring board 13 as shown in FIG. 1 (f) was obtained. The thickness of the multilayer printed wiring board 13 had a variation of 2% of the total thickness, which was ３ of the variation of 6% of the thickness of the conventional multilayer printed wiring board.

FIG. 5 is a profile showing the temperature distribution in the sectional direction of the head plate according to the second and third embodiments of the present invention. By locally changing the thickness of the heat generating portion of the end plate used in the second and third embodiments shown in FIGS. 3B and 3C, as shown in FIG. Can be made uniform, and the thickness accuracy can be further improved.

[0015]

The first effect is that the multilayer printed wiring board obtained by the present invention has twice the thickness accuracy as the conventional one. By improving the thickness accuracy, the variation in impedance of a printed circuit having the thickness accuracy as a parameter is improved, and a higher frequency signal can be passed with low noise. Further, since the thickness is uniform, it is possible to reduce malfunctions when mounting components on the printed wiring board. The reason is that in the manufacturing process where the multilayer printed wiring board is heated and pressurized and the prepreg is melted and bonded to form a multilayer, the heat conduction is delayed by directly heating the end plate that is in direct contact with the multilayer printed wiring board by the high-frequency induction heating method. Instead, an optimal temperature profile for melt-curing the prepreg is obtained in all multilayer printed wiring boards. In addition, by locally changing the thickness of the heat generating portion of the end plate, there is an effect that the temperature distribution in the end plate surface can be made uniform and the thickness accuracy can be further improved.

[Brief description of the drawings]

FIGS. 1A to 1F are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to first to third embodiments of the present invention in the order of steps.

FIG. 2 is a cross-sectional view illustrating the step of FIG.

FIGS. 3 (a) to 3 (c) are a perspective view and a sectional view of a head plate used in the first to third embodiments of the present invention, respectively.

FIG. 4 is a temperature profile of a laminate for explaining the printed wiring board according to the first embodiment of the present invention.

FIG. 5 is a profile showing a temperature distribution in a sectional direction of the head plate according to the second and third embodiments of the present invention.

6 (a) to 6 (f) are cross-sectional views shown in a process order illustrating an example of a conventional method for manufacturing a multilayer printed wiring board.

FIG. 7 is a cross-sectional view illustrating the step of FIG. 6 (f).

FIG. 8 is a cross-sectional view illustrating the step of FIG. 6 (f).

FIG. 9 is a temperature profile of the multilayer printed wiring board obtained by the manufacturing method of FIG. 6;

FIGS. 10A to 10D are cross-sectional views shown in the order of steps for explaining another example of a conventional method for manufacturing a multilayer printed wiring board.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 insulating plate 2 copper foil 3 double-sided copper-clad laminate 4 conductive circuit 5 printed wiring board for inner layer 6 prepreg 7 laminate 8 mirror plate 9 lamination jig 10 book 11 hot plate 12 pressure transmission plate 13 multilayer printed wiring board 14 metal 15 position Jig for alignment 16 Heating coil 17 4-layer printed wiring board 18 Pure steel plate 19 Stainless steel SUS316L

Claims (4)

[Claims] 1. An inner layer printed wiring board having conductive circuits formed on both sides or at least one inner layer printed wiring board having a conductive circuit formed on one side, comprising two conductive foils or the inner layer printed wiring board. Are arranged outside, and each metal foil and the printed wiring board for the inner layer are sandwiched by a pair of end plates via a prepreg, and one or more of these are stacked, sandwiched between pressure transmitting plates, and heated and pressed to form a multilayer. A method of manufacturing a multilayer printed wiring board having a process of manufacturing a multilayer printed wiring board having a process, comprising a step of directly heating the end plate by high-frequency induction heating to form a multilayer structure. Method. 2. The method according to claim 1, wherein said mirror plate is made of metal. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said end plate has a structure in which a plurality of metals or one or more types of metals and one or more types of insulators are bonded. 4. The method according to claim 3, wherein an arrangement ratio of the metal in the thickness direction of the end plate is partially changed.