JP2874581B2 - Circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for peeling a prepreg sheet and a polymer film in a method of manufacturing a circuit board used as a mask when a conductive film is filled by bonding a polymer film to both surfaces of the prepreg sheet. .

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller and higher in density, there has been a strong demand for higher density of circuit boards not only for industrial use but also for consumer use.

A method of manufacturing a circuit board by connecting an inner via hole with a conductive paste instead of the plated through hole, which has been a factor hindering the increase in the density of the circuit board, has been proposed (for example, JP-A-6-268345).

In this method of manufacturing a circuit board, a through hole is formed in a compressible porous prepreg sheet provided with a polymer film having releasability on both sides (hereinafter referred to as a releasable film). After the conductive paste is filled and the release film is peeled off, a metal foil is attached to both sides of the prepreg sheet and heated and pressed to electrically connect both sides of the substrate, and the metal foil is further patterned by etching to form a circuit. Things.

Hereinafter, a conventional method for manufacturing a circuit board will be described with reference to the drawings. 7A to 7F are process cross-sectional views showing a conventional process for manufacturing a circuit board. First,
As shown in FIG. 7A, a PET having a thickness of 12 μm is formed on both surfaces.
A porous prepreg sheet 11 having a size of 500 mm and a thickness of t1 mm, comprising a release film 12 having a silicone release layer formed on one surface of a polymer film such as (polyethylene terephthalate) is prepared. As the porous prepreg sheet 11, for example, a composite material in which a non-woven fabric of aromatic polyamide fibers is impregnated with a thermosetting epoxy resin is used.

Next, as shown in FIG. 7 (b), through holes 13 are formed in predetermined portions of the prepreg sheet 11 by using a laser processing method or the like.

Next, the prepreg sheet 11 is set on a table of a printing machine (not shown), and a conductive paste 14 is printed from above the release film 12 and filled in the through holes 13. At this time, the release film 12 on the upper surface plays a role of preventing contamination of the print mask and the prepreg sheet 11.

Next, as shown in FIG. 7D, the release sheets 12 on both sides of the prepreg sheet 11 are 2 m / m at room temperature.
peeled off at a speed of min. Then, as shown in FIG. 7 (e), a metal foil 15 such as a copper foil is adhered to both surfaces of the prepreg sheet 11, and heated and pressurized in this state, as shown in FIG. 7 (f). 11
The prepreg sheet 11 is compressed to a thickness t2 mm (t1> t2), and the metal foils 15 on both sides are electrically connected by the conductive paste 14.
At this time, the epoxy resin and the conductive paste 14, which are one component of the prepreg sheet 11, are hardened.

Thereafter, the metal foil 15 on both sides is selectively etched to form a circuit pattern (not shown), thereby obtaining a circuit board on both sides.

As described above, in the method of manufacturing a circuit board, the release film adhered to both surfaces of the prepreg sheet was formed with a through hole by laser processing or the like, and used as a mask when printing a conductor paste. Since peeling is performed later, adhesive strength that does not peel during laser processing or conductive paste printing, and peelability that can be easily peeled after filling with the conductive paste are important.

[0011]

However, in the above-mentioned conventional structure, even if the release property is not problematic immediately after the release film is bonded to the prepreg sheet, the resin component in the release layer or the prepreg sheet is not affected. Depending on the variation
When left for about two weeks, the adhesive strength increases, and the peeling failure of the release film occurs at the time of peeling.

For example, immediately after the release film is bonded to the prepreg sheet, the peel strength (180 ° peeling, peeling speed 2
(m / min) of 1.5 g / 30 mm width, after 2 weeks, of 30 g / 30 mm width, the release film breaks in all cases when peeled.

[0013] Further, the adhesive strength immediately after bonding varies due to the variation of the resin component in the release layer or the prepreg sheet, and the release film is peeled at the time of printing of the conductive paste, and the release failure of the release film occurs at the time of peeling. There was a problem.

The peeling of the release film during printing of the conductive paste occurs when the peel strength is around 0.5 g, resulting in poor contamination of the prepreg sheet by the conductive paste.

The present invention has been made to solve the above-mentioned conventional problems and is intended to stabilize the adhesiveness and peelability between a polymer film and a prepreg sheet, which are used as a mask when printing a conductive paste, and to realize a high-quality circuit board. It is an object of the present invention to provide a method for manufacturing a circuit board as described above.

[0016]

In order to achieve the above object, a method of manufacturing a circuit board according to the present invention is directed to a method for producing a circuit board comprising a thermosetting epoxy resin to which a release film having a release layer is adhered. > After making a through hole in the repreg sheet and filling the through hole with the conductive paste , the prepreg sheet is heated to 40 ° C to 90 ° C.
The release film is peeled off while being heated at the hot temperature , or a thermosetting resin bonded to a polymer film without a release layer.
Drilled holes in the prepreg sheet containing the epoxy resin, transmural
After filling the through-hole with the conductive paste , the prepreg sheet is heated at a heating temperature of 50 ° C. to 90 ° C., and then the polymer film is peeled off. Are electrically connected, and a circuit is formed by etching.

[0017]

According to the present invention constructed as described above, the prepreg sheet is kept at 40 ° C. to 90 ° when the release film is peeled off.
By heating at a heating temperature of ° C., the adhesive strength between the release film and the prepreg sheet is reduced, and stable release can be performed without breaking the release film.

Furthermore, by using a polymer film without a release layer, the adhesive strength to the prepreg sheet is increased and the adhesiveness is stabilized, so that the polymer film does not peel off during printing of the conductive paste, and Even if the polymer film has no layer, the solid thermosetting resin is softened and melted by heating the thermosetting resin in the prepreg sheet to a temperature higher than the melting start temperature in the prepreg state, and the adhesive strength is reduced, resulting in a decrease in the polymer film. Can be stably peeled without breaking.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a circuit board according to an embodiment of the present invention will be described below.

(First Embodiment) FIGS. 1A to 1F are sectional views showing the steps of manufacturing a circuit board according to a first embodiment of the present invention.

First, as shown in FIG. 1 (a), a release mold having a thickness of about 100 angstroms and a silicone release layer formed on a polymer film such as PET (polyethylene terephthalate) having a thickness of 12 μm on both sides. Film 2
A prepreg sheet 1 is prepared by impregnating a thermosetting epoxy resin into a non-woven fabric of a porous aromatic polyamide fiber having a size of □ 500 mm and a thickness of t1 mm.

In addition to PET for plastic films,
PI (polyimide), PEN (polyethylene naphthalate), PPS (polyphenylene sulphite), PP
(Polypropylene), PPO (polyphenylene oxide) or the like may be used. The prepreg sheet 1 may use a composite material in which glass fiber is impregnated with a thermosetting epoxy resin.

Next, as shown in FIG. 1B, a through hole 3 is formed in a predetermined portion of the prepreg sheet 1 by using a laser processing method or the like.

Next, the prepreg sheet 1 is placed on a table of a printing machine (not shown),
Is printed on the release film 2. At this time, the release film 2 on the upper surface plays a role of preventing contamination of the print mask and the prepreg sheet.

Next, as shown in FIG. 1D, the release film 2 on both sides is peeled off at a speed of about 2 m / min while the prepreg sheet 1 is heated to about 50 ° C. to 60 ° C. with hot air 6. . Here, a warm air method is used as the heating means, but an infrared heating method, a roll heating method, or the like may be used.

Then, as shown in FIG. 1 (e), a metal foil 5 such as a copper foil having a thickness of 35 μm is adhered to both surfaces of the prepreg sheet 1 and is heated and pressed in this state to thereby obtain the structure shown in FIG. As shown in FIG. 5, the prepreg sheet 1 and the metal foil 5 are bonded together, and the prepreg sheet 1 is compressed to a thickness t2 mm (t1> t2), and the metal foils 5 on both sides are electrically connected by the conductive paste 4. You. At this time,
The epoxy resin and the conductive paste 4 which are one component of the prepreg sheet 1 are cured.

By selectively etching the metal foils 5 on both sides to form a circuit pattern (not shown), a circuit board on both sides is obtained.

FIG. 2 is a graph showing the relationship between the heating temperature and the peel strength when the release film is peeled off. The measurement of the peel strength was performed by fixing a measurement object having a width of 30 mm and a length of about 100 mm to a temperature-controllable plate with a double-sided tape, and changing the temperature to 2 m / m.
180 degree peeling was performed at a speed of min. According to the JIS standard, the measurement speed of the peel strength of the metal foil 5 and the like is 60 mm / min, but the measurement was performed at the peel speed of the example.

For the measurement, the peel strength at room temperature immediately after the release film 2 was bonded to the prepreg sheet 1 was about 1.5 g.
A sample whose / 30 mm width increased to about 30 g / 30 mm width after 2 weeks and the release film was broken at the time of peeling was used.

The peel strength decreases in proportion to the temperature, and is lowest when the heating temperature is in the range of 50 ° C. to 60 ° C. (the peel strength is about 1.5
g / 30 mm width) and exceeds 60 ° C., the peel strength increases again and reaches a maximum at 90 ° C. (the peel strength is about 250 g / 30 g).
mm width), but the release film 2 is not broken.

The peeling strength decreases again because the resin component at 90 ° C. or higher begins to melt and the strength of the resin itself decreases. Under the heating conditions of the example, peeling was performed on 100 samples, but there was no breaking failure of the release film 2.

As described above, it was confirmed that the release film 2 can be peeled at 40 ° C. or higher without breaking. However, if the temperature exceeds 90 ° C., an increase in the amount of resin adhered to the release film 2 at the time of peeling or Since the stringing phenomenon of the resin component occurs, heating at a temperature of 90 ° C. or less is desirable, and the heating may be set at a level at which the curing of the epoxy resin in the prepreg sheet 1 does not cause a problem in a subsequent circuit board manufacturing process.

The heating time may be such that the prepreg sheet 1 reaches the desired temperature (in the embodiment, the desired temperature is reached in a few seconds). Similarly to the heating temperature, the curing of the epoxy resin in the prepreg sheet 1 is performed in a subsequent circuit. It may be set at a level that does not cause a problem in the substrate manufacturing process.

(Second Embodiment) FIGS. 3A to 3F are cross-sectional views showing the steps of manufacturing a circuit board according to a second embodiment of the present invention.

First, as shown in FIG. 3 (a), the size of a polymer film 7 such as PET (polyethylene terephthalate) having a thickness of 12 μm without a release layer on both sides is □
A prepreg sheet 1 having a thickness of 500 mm and a thickness t1 is prepared. For polymer films, besides PET, PI (polyimide), PEN (polyethylene naphthalate), PPS
(Polyphenylene sulfite), PP (polypropylene), PPO (polyphenylenoxide) and the like may be used.

As the prepreg sheet 1, for example, a composite material in which a woven glass fiber fabric is impregnated with a thermosetting epoxy resin is used. The prepreg sheet 1 is provided with two notches 8 as shown in FIG. Polymer film 7
As shown in an enlarged side view when viewed from the direction A, only the polymer film 7 on both sides is in contact (FIG. 6 (a)) or non-contact (FIG. 6 (b)). It exists in the state of.

Next, as shown in FIG. 3B, through holes 3 are formed at predetermined locations of the prepreg sheet 1 by using a laser processing method or the like.

Next, the prepreg sheet 1 is set on a table of a printing machine (not shown), and the conductive paste 4 is printed directly on the polymer film 7. At this time, the polymer film 7 on the upper surface plays a role of preventing contamination of the print mask and the prepreg sheet 1.

Next, as shown in FIG. 3D, the polymer film 7 on both sides is peeled off at a speed of about 2 m / min while the prepreg sheet 1 is heated to about 55 ° C. to 65 ° C. with warm air 6. Peeling can be easily performed by starting from the polymer film 7 at 9 parts of the two notches of the prepreg sheet 1.

Then, as shown in FIG. 3 (e), a metal foil 5 such as a copper foil having a thickness of 35 μm is adhered to both surfaces of the prepreg sheet 1 and heated and pressed in this state, thereby obtaining the structure shown in FIG. 3 (f). As shown in (2), the prepreg sheet 1 and the metal foil 5 are bonded together, and the prepreg sheet 1 is compressed to a thickness t2 mm (t1> t2), and the metal foils 5 on both surfaces are electrically connected by the conductive paste 4. At this time, the epoxy resin and the conductive paste 4 which are one component of the prepreg sheet 1 are cured.

The metal foil 5 on both sides is selectively etched to form a circuit pattern (not shown), whereby a circuit board on both sides is obtained.

FIG. 4 is a graph showing the relationship between the heating temperature during peeling and the peel strength. The peel strength was measured by fixing a measurement object having a width of 30 mm and a length of about 100 mm to a temperature-controllable plate with a double-sided tape, and performing 180 ° peeling at a speed of 2 m / min while changing the temperature.

The peel strength at room temperature of 20 ° C. was unmeasurable because the polymer film 7 was broken. In the example, 100 samples of the conductive paste 4 were printed, but there was no peeling of the polymer film 7 and no contamination of the prepreg sheet 3 by the conductive paste 4.

The peel strength at the time of heating was 100 g / 30 mm or more at a heating temperature of 50 ° C. or less, and the polymer film 7 was broken at the time of peeling, but the peel strength was sharply reduced at 55 ° C. (peel strength). (Approximately 8 g / 30 mm width), and the breakage of the polymer film 7 was eliminated. After 55 ° C., the peel strength increased and reached a maximum at 90 ° C. Although the peel strength at the maximum was about 300 g / 30 mm width, the polymer film 7 was not broken.

When the temperature exceeds 90 ° C., the resin component begins to melt and the strength of the resin itself decreases, so that the peel strength decreases again, but the polymer film 7 does not break. The change in the peel strength after 55 ° C. has almost the same tendency as that when the release film 2 is used.

The melting start temperature of the thermosetting epoxy resin in the prepreg sheet 1 used in the example was 8 ° C. /
As a result of measuring the viscosity characteristics at the time of min, it was found that since the heating temperature was close to 50 ° C., if the heating temperature exceeded the melting start temperature of the resin component, stable release properties without breaking of the polymer film 7 could be obtained. If the temperature exceeds 90 ° C., heating at 90 ° C. or lower is desirable because an increase in the amount of resin adhered to the polymer film 7 at the time of peeling and a stringing phenomenon of the resin component occur.

Also, the heating time may be such that the prepreg sheet 1 reaches the set temperature in the same manner as when the release film 2 is used, and the curing of the epoxy resin in the prepreg sheet 1 by heating is set at a level at which there is no problem. I just need.

Under the peeling conditions of the example, 100 samples were peeled, but there was no breakage failure of the polymer film 7.

In the first embodiment, the thickness of the release layer of the polymer film has been described as being about 100 Å. When the failure of the polymer film breaks down in the approaching low temperature range, the heating temperature should be set to be equal to or higher than the melting start temperature of the thermosetting resin in the prepreg sheet in the prepreg state as in the case of the polymer film without the release layer. I just need.

In the first and second embodiments, the results when the peeling speed is 2 m / min have been described. However, the inventor has confirmed that the peeling speed is up to 20 m / min. As the speed increases, the minimum temperature or the maximum temperature of the peel strength shifts by several degrees to the high temperature side, so it is known that a slight temperature adjustment may be performed according to the peel speed.

In the first embodiment, a prepreg sheet composed of a nonwoven fabric of aromatic polyamide fiber and a thermosetting resin is used. In the second embodiment, a prepreg sheet composed of a composite material of a woven fabric of glass fiber and a thermosetting resin is used. Similar results were obtained by using a prepreg sheet made of a composite material of a woven aromatic fiber fabric and a thermosetting resin and a composite material of a nonwoven glass fiber fabric and a thermosetting resin.

In the first and second embodiments, the prepreg sheet processed into a predetermined shape has been described. However, it is needless to say that the present invention can be applied to a continuous prepreg sheet.

Although the first and second embodiments have been described with respect to a double-sided circuit board, the present invention is also applicable to a multilayer circuit board which is used as a mask when filling a conductive paste by bonding a polymer film to both sides of a prepreg sheet. It goes without saying that you can do it.

[0054]

As described above, according to the method for manufacturing a circuit board of the present invention, a through-hole is formed in a prepreg sheet having a release film having a release layer on both sides bonded thereto, and the hole is filled with a conductive paste. After peeling off the release film while heating the prepreg sheet, the peel strength with the release film decreases even with the prepreg sheet stored for a long time, and stable release without breakage of the release film is achieved. it can.

Further, by using a polymer film having no release layer, the adhesive strength at the time of bonding with the prepreg sheet is greatly increased, and the polymer film is peeled off at the time of filling the conductive paste or the prepreg sheet is not covered with the conductive paste. Eliminates contamination failure and stabilizes polymer film without breakage even when polymer film without release layer is peeled off while heating above the melting start temperature of thermosetting epoxy resin in prepreg sheet in prepreg state High releasability and a high quality circuit board can be realized.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a first embodiment of a method of manufacturing a circuit board of the present invention.

FIG. 2 is a diagram showing a heating temperature and a peel strength of a pre-breg sheet and a release film in the same example.

FIG. 3 is a process sectional view showing a second embodiment of the method for manufacturing a circuit board of the present invention.

FIG. 4 is a diagram showing the heating temperature and the peel strength of a pre-breg sheet and a polymer film without a release layer in the same example.

FIG. 5 is a plan view of a prepreg sheet provided with cutouts at two corners in the embodiment shown in FIG. 3;

FIG. 6 is an enlarged side view of a cutaway portion of the prepreg sheet shown in FIG. 5 from a direction A.

FIG. 7 is a process sectional view showing a conventional circuit board manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Prepreg sheet 2, 12 Release film 3, 13 Through hole 4, 14 Conductive paste 5, 15 Metal foil 6 Hot air 7 Polymer film 8 Notch

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihiro Nishi 1006 Kadoma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor, Tamaki Kojima 1006, Kazuma, Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (56) References JP-A-6-268345 (JP, A) JP-A-4-40260 (JP, A) JP-A-3-149231 (JP, A) JP-A-1-116111 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 3/40 H05K 1/03

Claims (6)

(57) [Claims] 1. A through hole is made in a prepreg sheet containing a thermosetting epoxy resin provided on both sides with a release film having a release layer formed on a polymer film, and a conductive paste is applied to the through hole. After filling and releasing the release film, a method for manufacturing a circuit board, wherein both sides of the substrate are electrically connected by heating and pressing metal foils on both sides of the prepreg sheet, and a circuit is further formed by etching, 4 the prepreg sheet during the release film peeling
A method for manufacturing a circuit board, wherein the release film is peeled off while heating at a heating temperature of 0 ° C to 90 ° C. 2. A using a polymer film without parting layer instead of releasing film, peeling off the polymer film while the prepreg sheet was heated at a heating temperature of 50 ° C. to 90 ° C. during the polymer film peeling The method for manufacturing a circuit board according to claim 1. 3. The method for producing a circuit board according to claim 1, wherein the prepreg sheet is a composite material of a woven or nonwoven fabric mainly composed of an aromatic polyamide and a thermosetting epoxy resin. 4. The method for manufacturing a circuit board according to claim 1, wherein the prepreg sheet is a composite material of a woven or nonwoven fabric made of a glass material and a thermosetting epoxy resin. 5. The method for manufacturing a circuit board according to claim 1, wherein a part of the outer periphery of the prepreg sheet is removed , and at least one contact or non-contact portion between the plastic films on both surfaces is provided. 6. A polymer film of polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polypropylene, according to claim 1 or 2 circuit substrate manufacturing method according polyphenylene oxide.