JPH04360599A - Manufacturing apparatus for multilayer printed board - Google Patents

Abstract

PURPOSE:To make thickness of a board after adhesion uniform and to easily form a multilayer printed board having no interlayer deviation and no interlayer bubble by reducing in thickness a hot plate and eliminating generation of warpage of a hot plate due to insertion of a jig plate in steps of heating and pressurizing. CONSTITUTION:An apparatus for manufacturing a multilayer printed board, has two jig plates 2, 3 for holding a plurality of printed board 1 laminated through adhesive, a hot plate 14 for heating and pressuring a jig plate 4, and a support structure for holding the plate 14. The thickness of the plate 14 formed of an upper hot plate 12 and a lower hot plate 13. In this case, if a ratio of thickness to width of the plate 14 is 1/50 or less, it is sufficiently thin. Thus, a temperature distribution of the hot plate when the plate 4 for holding a laminate is inserted between the plates 14 becomes ignorably small, and no warpage of the plate 14 occurs inward. Even if warpage tends to occur, the hot plate is thin and low rigid, and hence it does not affect influence to the thickness of the board.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to an apparatus for molding a multilayer printed board for, for example, a large computer, and in particular,
The present invention relates to a multilayer printed board manufacturing device that can reduce interlayer misalignment and interlayer air bubbles in a multilayer printed board, and make the board thickness distribution uniform.

0002

2. Description of the Related Art Conventionally, multilayer printed circuit boards used in large-scale computers, etc., have been discussed, for example, in the June 1989 issue of Nichidai Microdevice magazine, pages 118 to 120. As shown in the figure, 20 to 40 layers of thin printed wiring boards of about 0.2 mm are laminated, and the size of the printed wiring boards reaches as much as 600 x 700 mm.

The printed wiring board used for such a multilayer printed board has a thickness of 0.1 mm, as shown in 1A of FIG.
0.05 mm thick on both sides of the insulating resin plate 1C of
It is constructed by bonding 1D conductors, and because it is thin as a whole, it has the property of being easily deformed by pressure and heat.

[0004] In this way, the multilayer printed board is made by bonding a thin printed wiring board 1A with an insulating adhesive 1B as shown in FIG.
It is formed by stacking many sheets together and applying heat and pressure.

First, in the conventional hot pressing method, there is a problem in that the pressure is concentrated at the periphery of the surface of the jig plate holding the laminate, and the pressure at the center is relatively low. The cause of this is thought to be a case of elastic body contact when there is friction between the jig plate and the hot plate. 59 pages
It is discussed in

In order to solve this problem, attempts have been made to make the pressure distribution uniform by making the central part of the hot plate convex, as described in, for example, Japanese Patent Application Laid-Open No. 59-191600.

The second problem occurs when the insulating adhesive 1B melts due to heating. That is, according to the inventors' study, and as reported in the University of Tokyo Mechanical Engineering Research Report Volume 23 (1988),
It has been revealed that the pressure distribution within the molten adhesive surface is high in the center and low in the periphery. This uneven pressure distribution causes warping, interlayer displacement, etc. in the multilayer printed board. The wiring density of each printed wiring board varies depending on the role of the wiring board, for example, whether it supplies power to a circuit or signals to wiring. of the board, e.g.
The coefficient of linear expansion and the temperature dependence of the rigidity of the base material are also different, and as a result, the degree of deformation in response to pressure is also different, resulting in a difference in the amount of deformation between each printed board, and a misalignment between the layers.

The third problem is the occurrence of voids (bubbles). Generally, printed circuit boards for large computers have a very high wiring density. Therefore, the gas trapped in the minute spaces created by the unevenness of the wiring conductor gets caught up in the insulating adhesive melted by heating and pressure, and remains as voids (bubbles) after the resin hardens.

[0009] The plating solution for through-hole plating, which is intended to pass through the same communication between layers, flows around the inner wall of such a bubble, causing a defect in which conductivity is lost in unnecessary locations.

A fourth problem is that the thickness distribution of the substrate after bonding is poor.

[0011] When the thickness of each printed board is thin and the number of layers of a multilayer printed board increases (as the number of printed boards to be laminated increases), the thickness between each layer is If the values vary, the capacitance between the layers will change, making it impossible to obtain the electrical characteristics set at the time of design. Furthermore, during drilling in the subsequent process, there is a risk that the drill may break due to the plate thickness gradient. Generally, the board thickness of a multilayer printed board after bonding is higher at the center within the plane of the board and thinner at the periphery. Therefore, the interlayer thickness has a distribution in which the in-plane central part is thicker and the peripheral part is thinner. In order to improve such thickness distribution, an attempt has been made to make the central part of the hot plate convex to make the thickness distribution uniform, as described in Japanese Patent Application Laid-Open No. 59-191600. When the agent material changes or the size of the substrate changes, it is necessary to change the convex state of the hot plate appropriately, but setting this condition has the disadvantage of requiring a large amount of time. was.

Conventionally, the following measures have been taken to deal with such problems of interlayer misalignment, residual bubbles, and plate thickness distribution.

For example, as described in Japanese Unexamined Patent Publication No. 59-87894, a cylinder for parallelism control between hot plates and a displacement detector are provided between each hot plate, and the displacement detector detects the The spacing between the hot plates was inputted into the controller, a parallelism correction value was obtained, and the pressure of the cylinder for controlling the parallelism between the hot plates was controlled to make the hot plates parallel to each other and suppress interlayer misalignment.

[0014] Furthermore, regarding air bubbles, Japanese Patent Application Laid-Open No. 57-118
As described in Japanese Patent No. 698, a vacuum device was used to evacuate the gas between the hot plates.

[0015] Furthermore, as another countermeasure,
As described in Publication No. 247, a method has been devised in which a printed wiring board laminate is placed inside a heat-resistant film, vacuum-suctioned, and then heated and pressurized with high-temperature, high-pressure gas in a high-pressure tank, without using a hot plate. There is.

Furthermore, as a method of reducing the thickness distribution of the substrate after adhesive molding, there is a method of improving the thickness distribution by changing the central part of the hot plate into a convex shape, as described in Japanese Patent Application Laid-open No. 191600/1983. be.

[0017]

Problems to be Solved by the Invention The above-mentioned prior art lacks consideration of the following matters, and has the problem of not being able to sufficiently suppress interlayer deviations, interlayer bubbles, and plate thickness distribution of the substrate.

1) In order to uniformly pressurize the laminate, the measure of making the central part of the hot plate convex requires a lot of experimentation and trial and error even in adjusting the pressure distribution at room temperature, and also The pressure distribution is different before and during melting of the adhesive, which makes pressure distribution adjustment performed at room temperature even more difficult, and as a result, interlayer displacement, interlayer bubbles, and plate thickness distribution cannot be sufficiently suppressed.

2) Even if the pressure distribution is adjusted to be uniform at room temperature, the pressure distribution will be different when the insulating adhesive is melted at high temperatures, which will have a negative effect on the thickness distribution of the substrate after adhesive molding.

In particular, the inventor's research has revealed that immediately after heating the laminate, the following warping of the hot plate occurs, resulting in poor plate thickness distribution. In other words, when a jig plate holding the laminate is inserted into a preheated hot plate, the temperature of the jig plate is low before insertion, so the jig plate and The surface temperature of the hot plate on the contacting surfaces decreases. Therefore, a temperature distribution occurs in the thickness direction of the hot plate, and warpage occurs in the in-plane direction of the hot plate. It has been found that due to this warpage, the thickness of the laminate becomes thinner at the periphery, and conversely becomes thicker at the center.

In order to make the thickness distribution of the substrate uniform due to such causes, attempts have been made to make the central part of the hot plate convex, but this increases the resin pressure distribution during bonding (the central part (higher at the periphery), this has a negative effect on the interlayer misalignment of the substrate, so determining the convex state requires multiple adhesion experiments, and if the adhesive material is changed, etc. There is also a possibility that adhesion cannot be achieved under the determined conditions.

An object of the present invention is to prevent the warpage of the hot plate due to the insertion of the jig plate during the bonding of the laminate, that is, the process of heating and pressurizing, so that the thickness of the board after bonding is uniform. The object of the present invention is to provide an apparatus for easily forming a multilayer printed board without interlayer misalignment and interlayer bubbles.

[0023]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for minimizing warping during bonding of a hot plate that supplies the heat and pressure necessary for bonding laminates of multilayer printed boards. , the thickness of the hot plate was reduced. Note that this is sufficiently effective if the ratio of the thickness of the hot plate to the width of the plate is 1/50 or less.

[0024]

[Function] As the thickness of the hot plate becomes thinner, the temperature distribution that occurs in the thickness direction of the hot plate when a jig plate holding the laminate is inserted between the hot plates becomes negligibly small. Does not cause warping in the in-plane direction of the hot plate. Further, even if warpage occurs, the thickness of the hot plate is thin and the rigidity is low, so that it cannot affect the thickness of the board. Therefore, the thickness distribution of the substrate after adhesive molding can be made uniform.

[0025]

[Examples] Examples of the present invention will be described below.

First, the problems of the conventional bonding method and device are shown in FIG.
This will be explained using FIG. FIG. 3 is a schematic diagram showing an example of a conventional adhesive press.

A laminate 1 in which pre-wired printed wiring boards and insulating adhesive are alternately stacked is supported by a jig plate 4 consisting of an upper jig plate 2 and a lower jig plate 3. A hot plate 7 composed of an upper hot plate 5 and a lower hot plate 6 is heated by an electric heater, steam, heat medium oil, etc., and transmits this heat to the jig plate 4.

Further, the load necessary for bonding is transmitted from the main ram 8 to the lower bolster 9B and further to the jig plate 4. The entire adhesive load is applied to the tie bar 10 via the upper bolster 9A.
It is configured to be received by In addition, in order to prevent the heat of the hot plate 7 from transferring to the press body, an upper heat insulating plate 11A is installed between the upper bolster 9A and the upper hot plate 5, and also between the lower bolster 9B and the lower hot plate 6. A lower heat insulating board 11B is installed between them.

The state shown in FIG. 3 is a stable thermal state of the hot plate. On the other hand, immediately after the jig plate is inserted between the hot plates, it is in a thermally unsteady and unstable state.

FIG. 4 is a schematic diagram showing an example of a conventional adhesive press immediately after the jig plate 4 at room temperature is inserted into the hot plate 7 heated and maintained at a high temperature.

Immediately after inserting the jig plate 4 at room temperature between the hot plates heated and held at a high temperature, the temperature of the jig plate 4 is lower than that of the hot plate 7, so the jig plate of the hot plate 7 The temperature of the surface in contact with 4 is rapidly cooled. Therefore, a temperature distribution occurs in the thickness direction of the hot plate 7. That is, the surface in contact with the jig plate 4 is low and the surface on the opposite side is high, which causes the hot plate 7 to warp as shown in FIG. Due to this warpage, the thickness of the periphery of the laminate 1 supported on the jig plate 4 becomes thinner. After this, the warpage of the hot plate 7 becomes smaller as the temperature distribution in the thickness direction of the hot plate 7 becomes smaller (as time passes), but
Once the plate thickness has been reduced, it will not return to its original state, and the plate thickness distribution will remain even after bonding.

As described above, the occurrence of warpage in the hot plate is a physical phenomenon as long as the thickness of the hot plate 7 exists, but as the thickness of the hot plate becomes thinner, the occurrence of warpage will be reduced. It should be smaller and have less influence on the laminate 4.

FIG. 1 is an explanatory diagram showing an example of an adhesive press having a hot plate.

The hot plate 14 composed of the upper hot plate 12 and the lower hot plate 13 is characterized by being thinner than the thickness of the conventional hot plate 7 as shown in FIG. At this time, the hot plate 14
If the ratio of plate thickness to plate width is 1/50 or less, it can be said that the plate is sufficiently thin. The warpage of the hot plate of the adhesive press configured with such a hot plate 14 can be reduced to 1/10 or less of the conventional warp because the temperature distribution in the thickness direction of the hot plate 14 is small. Figure 4
calculates the temperature distribution in the thickness direction of the hot plate 7 when the jig plate 4 is inserted between the hot plates 7 of a conventional adhesive press, and the temperature distribution of the hot plate 14 under the same conditions (difference method) This is a comparison. Note that the temperature of the hot plate before inserting the jig plate 14 is
The temperature of the jig plate was 130°C, the temperature of the jig plate was 20°C, and the thickness of the jig plate was constant at 10 mm. In addition, the thickness of the conventional hot plate 7 is 6
The thickness of the hot plate 14 was 10 mm. As shown in FIG. 4, in the hot plate, the temperature distribution between the surface of the hot plate that comes into contact with the jig plate and the surface opposite thereto is significantly small.

Based on this result, the warpage of the hot plate was determined from equations (1) and (2) based on the plane stress process.

[0036]

[Math 1]

It was assumed that no thermal stress was generated on the hot plate. The results are shown in FIG. FIG. 5 compares the warpage of a conventional hot plate and the warp of the hot plate of the present invention. Figure 5
As shown in Figure 2, the warpage of the hot plate can be significantly reduced by reducing the thickness of the hot plate.

As a result, the thickness distribution of the substrate after molding can also be reduced to about 1/3 of that of the conventional method.

[0039]

[Effects of the Invention] By using the multilayer printed board manufacturing apparatus according to the present invention, the thickness of the board after bonding can be made uniform;
Since there is no need to worry about changes in capacitance between the layers of the board, the electrical characteristics set at the time of design can be obtained, and not only is the electrical reliability high, but it is also easy to perform drilling in the post-process, and there is no need to worry about drill breakage. Therefore, a multilayer printed board with high workability can be manufactured.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an adhesive press according to an embodiment of the present invention;

[Fig. 2] An explanatory diagram of a conventional adhesive press,

FIG. 3 is an explanatory diagram showing the warpage of the hot plate after inserting the jig plate in a conventional adhesive press;

FIG. 4 is an explanatory diagram of a calculation example of the temperature distribution of the hot plate of the present invention,

[
FIG. 5 is an explanatory diagram of an example of calculating the warpage of the hot plate of the present invention,

[Figure 6]
Cross-sectional view of printed wiring board,

FIG. 7 is a perspective view of a laminate of printed wiring boards.

[Explanation of symbols]

1...Laminated body, 2...Upper jig plate, 3...Lower jig plate, 4...Jig plate, 12...Top hot plate, 13...lower heating plate, 14...Hot plate.

Claims (2)

[Claims] Claim 1: Two jig plates for holding together a plurality of printed boards laminated with an adhesive, a heating plate for heating and pressurizing the jig plates, and a support structure for holding the jig plates. In the multilayer printed board manufacturing apparatus equipped with the above, in order to minimize the thickness distribution of the board after bonding due to the effect of warping of the hot plate during bonding, use a thinner hot plate. Multilayer printed board manufacturing equipment featuring: 2. The multilayer printed board manufacturing apparatus according to claim 1, wherein the ratio of the thickness of the hot plate to the width of the hot plate is 1/50 or less.