JPH06344501A - Production of laminated sheet - Google Patents

Abstract

PURPOSE:To produce a laminated sheet of a low dielectric constant enhanced in thickness accuracy, reduced in thickness irregularity, reduced in the coefficient of linear expansion in its thickness direction, enhanced in the bonding strength of a metal foil and a prepreg, solder heat resistance and thermal impact resistance and prevented from the penetration of a chemical soln. CONSTITUTION:A base material 1 is impregnated with a PTFE dispersion and, after the impregnated base material is dried, it is baked at a temp. higher than the m.p. of PTFE to form a first layer 2 holding a necessary amt. of PTFE and the surface of the first layer is further impregnated with the PTFE dispersion and the impregnated layer is dried at a temp. lower than the m.p. of PTFE to form a second layer 3 holding a necessary amt. of PTFE. The surface of the second layer 3 is impregnated with the PFA dispersion and, after the impregnated layer is dried, it is baked at a temp. higher than the melting points of PFA and PTFE to form a third layer 4 holding a necessary amt. of PFA to obtain a prepreg 5. A metal foil 6 is arranged on at least the single surface of the prepreg 5 and the whole is pressed at a temp. higher than the melting points of PFA and PTFE under a high pressure.

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 laminate such as a low dielectric constant laminate used as a high frequency printed wiring board.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a laminated plate, there are various manufacturing methods as described below.

The first manufacturing method is to use a PTFE resin (polytetrafluoroethylene, tetrafluoride resin) as a base material.
Impregnated with prepreg (pre-
preg) is formed, and a PFA resin (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin) film or FEP resin (tetrafluoroethylene / hexafluoropropylene copolymer resin) film is interposed between multiple layers of prepreg, and In this method, the above film is also interposed between the metal foil and the prepreg arranged in the outer layer, and the laminate is manufactured by laminating and molding.

According to this first manufacturing method, by interposing the film, the adhesive strength between the metal foil and the prepreg is maintained, and the adhesive force between the prepreg layers is maintained,
On the other hand, there is an advantage that the resin content ratio in the laminated plate can be adjusted. On the other hand, the above-mentioned film is generally melt-kneaded with a screw extruder and injection-molded through a T-type die.
During the manufacturing process of this film, a considerable amount of metal particles and metal powder are mixed in the film, and since the metal particles and metal powder have conductivity, they cause a short circuit of the printed circuit board, a disconnection, etc. There was a problem that it was difficult to use.

In the second manufacturing method, a base material is impregnated with a first fluororesin (eg, PTFE), dried and fired, and then PFA or FEP is used as a second fluororesin.
Is placed on the outermost layer of the prepreg formed by impregnating and drying and firing the metal foil, and then laminating is performed to produce a laminated plate.

According to this second manufacturing method, the first fluororesin impregnated into the base material is dried and then fired at a temperature equal to or higher than the melting point of the resin. Since the surface energy is low and the wettability is extremely deteriorated, even if an attempt is made to hold another PFA or FEP on the fluororesin, the film is dropped during the drying and firing steps, and a uniform and highly accurate film is obtained. Is difficult to form, and the adhesive strength between the prepreg and the metal foil, the mutual adhesive strength between the prepregs, and the resin content are partially different, and the characteristic values vary, so a laminated board with stable performance cannot be obtained. There was a problem.

A third manufacturing method comprises forming a fluororesin layer on the surface of a cloth-like substrate, forming a prepreg in the vicinity of the surface of the fluororesin layer which is not sintered, and forming a metal foil on the surface of the prepreg. After arranging, it is a method of manufacturing a laminated board by heating and pressurizing and adhering the above metal foil to the prepreg.

According to the third manufacturing method, the fluororesin layer impregnated in the cloth-like base material is unsintered only near the surface thereof, and the core portion of the base material and the vicinity of the base material are sintered. According to this third manufacturing method, there is an advantage that the adhesive strength between the prepreg and the metal foil can be secured to some extent, but on the other hand, in a large-sized laminated plate, it is difficult to obtain a uniform adhesive force over the entire surface, In the case of a laminate with a large variation and a low resin content, the chemical solution penetrates from the resin surface after the metal foil is removed by etching during circuit formation, and the solder heat resistance is poor and the metal foil swells. There is a problem that the defect of occurs. In addition, since a sintered layer and a non-sintered layer are mixed in the prepreg, there is a problem that defects such as warp and twist are likely to occur when the laminated plate is thin.

In the fourth manufacturing method, the base material is impregnated with the first fluororesin, dried and sintered, and the second fluororesin having a lower melting point than the first fluororesin for the upper layer. To form a prepreg, and after placing a metal foil on the prepreg, laminate molding is performed under a temperature condition that is lower than the melting point of the first fluororesin and higher than the melting point of the second fluororesin. This is a method for producing a laminated board.

According to the fourth manufacturing method, since the first fluororesin described above exerts a cushioning property due to the shape memory property peculiar to the resin at the time of laminating and pressurizing the laminated plate, the characteristics of the laminated plate may vary and may not be uniform. In addition to being stable, since the first fluororesin is fired at a temperature equal to or higher than the melting point of the first fluororesin during firing, the surface energy is low and the wettability is deteriorated. Even if the second fluororesin is held, there is a problem that it becomes difficult to form a uniform film with high accuracy because it falls off during the drying and baking steps.

On the other hand, in order to obtain a low dielectric constant substrate, it is necessary to form a prepreg having a high resin content, but it has been difficult to form a prepreg having a high resin content in the prior art. That is, when the glass cloth base material is impregnated with the resin, and then dried and sintered repeatedly, the resin shrinks in the resin sintering step described above, so that it becomes possible to thickly coat the resin on the glass cloth base material. However, by repeating the above-mentioned operation, the base material is not extinguished by the above-mentioned contraction force and is deformed in a wavy shape, so that unevenness in thickness is generated in the formed prepreg, and the thickness accuracy is deteriorated.

Therefore, conventionally, as seen in the above-described first manufacturing method, a method of interposing a PFA film or a FEP film between each layer and between the prepreg and the metal foil has been adopted. According to such a conventional method, a PFA film or a resin layer obtained by melting or softening a PEP film or an FEP film, which is relatively difficult to be extremely thin, is heated and pressed at a melting temperature or higher of the resin film of PFA or FEP during lamination molding. The (PFA or FEP resin layer) is in a fluidized state and flows out. Due to the outflow of this resin, the substrate thickness becomes non-uniform, and sufficient thickness accuracy cannot be ensured.

When pressure is applied under high temperature and low pressure conditions in order to solve such a problem, voids (small holes) remain between the layers and the joining becomes insufficient, so that the prepreg itself is Resin unevenness occurs, swelling of the metal foil at the time of bonding or solder bonding of the metal foil, interlayer cracks, delamination, etc., both solder heat resistance and thermal shock resistance are low, and further, due to a decrease in the density of the entire laminate, There is a problem in that the chemical solution penetrates during etching.

[0014]

SUMMARY OF THE INVENTION According to the present invention, a prepreg comprises a first layer of PTFE, a second layer of PTFE, and a PFA.
3rd layer structure with the 3rd layer of the above, and the PTFE 2nd layer is dried under low temperature conditions without sintering to make the retention of the PFA 3rd layer good, and the PFA 3rd layer has a film interposed structure. Rather than being formed by dispersion impregnation, drying, and firing, high-temperature and high-pressure pressing is possible, and a unique method of pressurizing under high-temperature and high-pressure conditions above the melting points of PTFE and PFA during lamination pressing provides high thickness accuracy. The thickness variation is small, the linear expansion coefficient in the thickness direction is small, the adhesive strength between the metal foil and the prepreg is strong, the solder heat resistance and the thermal shock resistance are both high, and the chemical solution does not penetrate. An object of the present invention is to provide a method for manufacturing a laminate having a low dielectric constant.

[0015]

The present invention provides a substrate with PT.
After impregnation with FE dispersion and drying, PTF
A first step of firing under conditions of a temperature higher than the melting point of E and repeating the above-mentioned impregnation, drying and firing to form the first layer having a required resin retention amount; and after impregnating the surface of the first layer with PTFE dispersion , A second step of drying at a temperature lower than the melting point of PTFE and repeating the above-mentioned impregnation and drying to form a second layer having a required resin retention amount, and PF on the surface of the second layer.
After impregnation with A dispersion and drying, the PFA
And firing at a temperature higher than the melting point of the above-mentioned PTFE, and repeating the above-mentioned impregnation, drying and firing to form a third layer having a required resin holding amount, and a third step of forming a prepreg, and at least one surface of the prepreg. A fourth aspect of the present invention is a method for producing a laminated plate, which comprises a fourth step in which, after arranging the metal foil, the temperature is higher than the melting points of PTFE and PFA, and high-pressure pressing is performed.

[0016]

According to the present invention, the above prepreg has a three-layer structure of the first layer of PTFE, the second layer of PTFE, and the third layer of PFA, and the second PTFE layer is sintered. Without a dry treatment at a temperature lower than the melting point of PTFE,
Good retention of the FA third layer, and impregnation of the PFA third layer with PFA dispersion instead of film interposing means,
Since it is formed by drying and firing, high-temperature and high-pressure pressing at the time of lamination becomes possible.

Moreover, during lamination press, PTFE and P
Since it is a method of pressurizing under high temperature and high pressure condition than each melting point of FA, thickness accuracy is high, thickness variation is small, linear expansion coefficient in the thickness direction is small, and metal foil and prepreg are bonded. It is strong, has high solder heat resistance and high thermal shock resistance, and has the effect of preventing the infiltration of chemicals.

Further, since the laminated plate is manufactured by the above high temperature and high pressure press, there are no voids (small holes) between the layers, the bonding between the layers is sufficient, the resin unevenness of the prepreg itself does not occur, and when the solder is adhered. Swelling of metal foil, interlayer cracks,
There is an effect that delamination can be prevented.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. The drawing shows a method for manufacturing a laminated board, and in the first step S1 shown in FIG. 1, a glass cloth substrate 1 having a basis weight of 48 g / m ² (see FIG.
(Refer to FIG. 3), which is impregnated with PTFE dispersion and dried, and then baked (sintered) at 380 ° C., which is higher than the melting point of PTFE, 327 ° C.
The first layer 2 is formed by repeating the above-mentioned impregnation, drying and sintering until it becomes 0 vol%.

Next, in a second step S2 shown in FIG. 1, after impregnating the upper and lower surfaces of the above-mentioned first layer 2 with PTFE dispersion, 305 ° C. which is lower than the melting point of PTFE of 327 ° C.
The resin content as required resin retention is 76 vo
The second layer 3 is formed by repeating the above-mentioned impregnation and drying until it reaches 1%.

Next, in the third step S3 shown in FIG. 1, PFA dispersion is impregnated on the upper and lower surfaces of the second layers 3 and 3 and dried, and then the melting point of this PFA is 310 ° C. and the above-mentioned PTFE. The resin content rate of 80 as a necessary resin holding amount is obtained by firing (sintering) at 380 ° C, which is higher than the melting point of 327 ° C
The above-mentioned impregnation, drying and sintering are repeated until the vol% is reached to form the third layer 4 and the prepreg 5.

Next, in a fourth step S4 shown in FIG. 1, for example, two layers of the above-mentioned prepreg 5 are superposed, and as shown in FIG. 3, a metal foil is formed on the outermost layer of the two-layer polymerized prepregs 5 and 5. After arranging the Cu foils 6 and 6, the above PTF
The melting point of E is 380 ° C., which is higher than the melting point of 327 ° C. of E, and the melting point of 310 ° C. of PFA.
A 4 mm copper foil-clad laminate 7 was produced.

On the other hand, as a comparative example, the first step S1 shown in FIG.
With a resin content of 76 vol%, 6 layers of this prepreg were superposed, a PFA film was placed on the outside, a Cu foil as a metal foil was placed on the outermost layer, and then high-pressure pressing was performed at 380 ° C. A plate (Comparative Example 1) was manufactured, and as another Comparative Example, the resin content was 70 vol% in the first step S1 shown in FIG.
A laminated plate (Comparative Example 2) was produced by arranging 6 layers of films alternately so that a PFA film was formed between the outermost Cu foil and 340 ° C. and a surface pressure of 10 kgf / cm ² . Table 1 below shows the results of various measurements and tests performed on the above-described example product (Example 1) and the comparative products of Comparative Example 1 and Comparative Example 2.

[0024]

[Table 1]

As is clear from Table 1 above, the laminated plate 7 manufactured by the manufacturing method of the present embodiment has high thickness accuracy, and variations in plate thickness of the laminated plate 7 (R = maximum value-minimum value). )
Is as small as 0.007 mm and the linear expansion coefficient in the thickness direction is 20
The Cu foil 6 has a small peel strength of 0 × 10 ⁻⁶ / k at both room temperature and 200 ° C., has excellent solder heat resistance, and has a thermal shock resistance by repeated tests at a low temperature of 20 ° C. and a high temperature of 260 ° C. ( Through-hole reliability) is as high as 60 cycles, and there is no chemical solution penetration in the chemical solution penetration test measured by ultraviolet rays immersed in fluorescent flaw detection.
Excellent results could be obtained for 2.

Further, according to the manufacturing method of the above-mentioned embodiment, it is possible to manufacture the laminated plate 7 having a resin content of 80 to 90 vol%, and the sintering step (the first step S1 and the third step S in FIG. 1).
3), the prepreg 5 is formed, so that the resin coating is smooth and has no voids. If the prepreg 5 is contaminated, the surface can be wiped and the process can proceed to the next step.

In summary, the above prepreg 5 is PT
The first layer 2 of FE, the second layer 3 of PTFE, and the third layer 4 of PFA are made into a three-layer structure, and the PTFE second layer 3 is dried without being sintered at a temperature lower than the melting point of PTFE. The PFA third layer 4 is held well, and the PFA third layer 4 is maintained.
Since the layer 4 is formed by impregnation of PFA dispersion, drying and firing, not by means of a film interposing means, high temperature and high pressure pressing at the time of lamination becomes possible.

Moreover, at the time of laminating press, PTFE and P
Since it is a method of pressurizing under high temperature and high pressure condition than each melting point of FA, thickness accuracy is high, thickness variation is small, linear expansion coefficient in the thickness direction is small, and metal foil and prepreg are bonded. It is strong, has high solder heat resistance and high thermal shock resistance, and has the effect of preventing the infiltration of chemicals.

Further, since the laminated plate 7 is manufactured by the above high temperature and high pressure press, there are no voids (small holes) between the layers, the bonding between the layers is sufficient, the resin unevenness of the prepreg itself does not occur, and at the time of solder bonding, etc. The effect of preventing swelling of the metal foil, inter-layer cracks, and inter-layer peeling is effective.

FIGS. 4, 5 and 6 show another embodiment of the method for manufacturing a laminated plate, in which the prepreg 5 shown in the previous embodiment is used as the outer layer prepreg 8 (see FIG. 4). The inner layer prepreg 9 (see FIG. 5) is separately formed by the method described below, and the laminated plate 10 (see FIG. 6) is manufactured using the outer layer prepreg 8 and the inner layer prepreg 9 described above. is there.

The manufacturing method of this laminated plate will be described in detail below. Since the outer layer prepreg 8 is the same as the manufacturing method of the prepreg 5 of the previous embodiment, the same parts as in the previous figure are not shown in FIG. The same numbers are assigned and detailed explanations thereof are omitted.

The inner layer prepreg 9 is, as shown in FIG.
A glass cloth 11 having a basis weight of 48 g / m ² was impregnated with PTFE dispersion and dried, and then baked (sintered) at 380 ° C., which is higher than the melting point of PTFE of 327 ° C., and a resin content rate of 70 vol as a required resin retention amount. The above-mentioned impregnation, drying and sintering are repeated until the content of the prepreg 9 reaches 10% to form the inner layer prepreg 9 having the PTFE layer 12.

Next, as shown in FIG. 6, two layers of the above-mentioned inner layer prepreg 9 are superposed on the central portion, and the above-mentioned outer layer prepregs 8 and 8 are superposed on the upper and lower surfaces of each of the inner layer prepregs 9 and 9. After further arranging the Cu foils 6 and 6 as metal foils on the outer surfaces of the outer layer prepregs 8 and 8,
The above melting point of PTFE is 327 ° C. and the melting point of PFA is 310.
A copper foil-clad laminate 10 having a total thickness of 0.6 mm was manufactured by pressing at 380 ° C., which is higher than 0 ° C., and high pressure.

Various kinds of comparative products of the example product (Example 2) manufactured in this way and Comparative Example 1 and Comparative Example 2 (the manufacturing method of each comparative product is the same as described above) The following Table 2 shows the results of the measurement and the test.

[0035]

[Table 2]

As is apparent from Table 2 above, the laminated plate 10 manufactured by the manufacturing method of this embodiment is the laminated plate 10
Thickness variation (R = maximum value-minimum value) of 0.010
mm, the thickness accuracy is high, the linear expansion coefficient in the thickness direction is small at 180 × 10 ⁻⁶ / k, the peel strength of the Cu foil 6 is strong at both room temperature and 200 ° C., and it has excellent solder heat resistance. At the same time, the thermal shock resistance (through hole reliability) of the repeated test of low temperature 20 ° C and high temperature 260 ° C is as high as 60 cycles, and there is no chemical solution penetration in the chemical solution penetration test which was measured by UV after being immersed in fluorescent flaw detection. In each case, excellent results were obtained with respect to Comparative Examples 1 and 2.

In summary, the above-mentioned outer layer prepreg 8
The first layer 2 of PTFE, the second layer 3 of PTFE, and the PF
A third layer 4 of A is formed into a three-layer structure, and the PTFE second layer 3 is dried without being sintered at a temperature lower than the melting point of PTFE to improve the retention of the PFA third layer 4 and the PFA.
Since the third layer 4 is formed by impregnation of PFA dispersion, drying and firing, not by means of a film interposing means, high temperature and high pressure pressing during lamination becomes possible.

Moreover, at the time of laminating press, PTFE and P
Since it is a method of pressurizing under high temperature and high pressure condition than each melting point of FA, thickness accuracy is high, thickness variation is small, linear expansion coefficient in the thickness direction is small, and metal foil and prepreg are bonded. It is strong, has high solder heat resistance and high thermal shock resistance, and has the effect of preventing the infiltration of chemicals.

The laminated plate 10 is produced by the high temperature and high pressure press described above.
Since it is manufactured, there are no voids (small holes) between layers, sufficient bonding between layers, no resin unevenness of the prepreg itself occurs, and swelling of metal foil during solder bonding, interlayer cracks, delamination There is an effect that can be prevented.

In the correspondence between the constitution of the present invention and the above-mentioned embodiment, the base material of the present invention is the glass cloth base material 1 of the embodiment.
In the same manner, the metal foil corresponds to the Cu foil 6,
The prepreg corresponds to the prepreg 5 of the first embodiment and the outer layer prepreg 8 of the second embodiment, but the present invention is not limited to the configuration of the above-described embodiment.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for manufacturing a laminated board of the present invention.

FIG. 2 is a sectional view of a prepreg.

FIG. 3 is a cross-sectional view of a laminated board manufactured by the manufacturing method of the present invention.

FIG. 4 is a cross-sectional view of an outer layer prepreg showing another embodiment of the method for manufacturing a laminated board of the present invention.

FIG. 5 is a sectional view of an inner layer prepreg showing another embodiment of the method for manufacturing a laminated board of the present invention.

FIG. 6 is a cross-sectional view of a laminated board manufactured according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass cloth base material 2 ... 1st layer 3 ... 2nd layer 4 ... 3rd layer 5 ... Prepreg 6 ... Cu foil 8 ... Outer layer prepreg

Claims (1)

[Claims] 1. A base material is impregnated with PTFE dispersion, dried, and then fired at a temperature higher than the melting point of PTFE, and the above impregnation, drying and firing are repeated to form a first layer having a required resin retention amount. And a step of impregnating the surface of the first layer with PTFE dispersion, followed by drying under a temperature lower than the melting point of PTFE, and repeating the impregnation and drying to form a second layer having a necessary resin retention amount. The second step,
After the surface of the second layer is impregnated with PFA dispersion and dried, the PFA dispersion is baked at a temperature higher than the melting points of the PFA and the PTFE, and the impregnation, drying and baking are repeated to obtain a third resin having a necessary resin retention amount. The third step of forming a layer and forming a prepreg, and arranging a metal foil on at least one surface of the prepreg, and then applying the PTFE and P
Pressing under high temperature condition and higher than melting point of FA
A method for manufacturing a laminated board, which comprises: