JP2006278688A - Cushioning material, and method for manufacturing wiring plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cushioning material having excellent heat resistance and cushioning properties even if a pressing temperature exceeds a melting point of solder, and a method for manufacturing a wiring plate for imparting uniform pressure to the wiring plate even when it is pressed at a temperature of exceeding the melting point of solder. <P>SOLUTION: The cushioning material is used when manufacturing the wiring plate. A heat-resistant release layer 1, a first resin layer 2 having a first glass transition temperature, and a second resin layer 3 having a second glass transition temperature higher than the first glass transition temperature, are sequentially laminated in the cushioning material. The cushioning material is used in the method for manufacturing a wiring plate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cushion material and a method for manufacturing a wiring board.

  With recent high integration and high-density mounting of electronic devices, the multilayer of flexible printed circuit boards used therefor has progressed, and flexible printed circuit boards having a multilayer structure have been put into practical use.

  As the structure of the multilayer flexible printed circuit board, a double-sided flexible printed circuit board is used as a core board, and a single-sided flexible printed circuit board is laminated on both sides via an interlayer adhesive. Among them, a multilayer via plate having a stacked via structure, which is advantageous for miniaturization and high density, has begun to attract attention. There are various via bonding methods such as a paste system and a plating system, but a metal-bonded substrate is considered good because of high connection reliability. As an example of the metal joining, there is a method of joining the layers by melting solder.

Conventional multi-layer flexible printed circuit boards have been connected through through-holes or build-up. Therefore, the press temperature for multilayering is generally a temperature at which the interlayer adhesive is cured and is generally 200 ° C. or less (see, for example, Patent Document 1).
On the other hand, in the metal connection of the multilayer board having a stacked via structure by melting the solder and connecting the metal layers, the bumps formed on the single-sided flexible printed circuit board and the opposing lands are joined by the solder. In order to melt and join the solder, pressing is performed at a temperature equal to or higher than the melting point (220 ° C.) of the solder. Therefore, excellent heat resistance and cushioning properties are required even for the cushioning material used in the press even above the melting point of the solder. In such a high-temperature press, when a cushion material having poor heat resistance is used, there is a case where pressure cannot be uniformly applied to the wiring board due to insufficient cushioning properties.

Published Japanese Patent Application Laid-Open No. 2004-288896

An object of the present invention is to provide a cushioning material having excellent heat resistance and cushioning properties even when the melting point is higher than the melting point of solder.
Moreover, the objective of this invention is providing the manufacturing method of the wiring board which can provide a uniform pressure to a wiring board even when it presses above melting | fusing point of solder.

Such an object is achieved by the present invention described in the following (1) to (7).
(1) A cushioning material used in manufacturing a wiring board, which is a release layer having heat resistance, a first resin layer having a first glass transition temperature, and a second glass higher than the first glass transition temperature. A cushioning material, wherein a second resin layer having a transition temperature is laminated in this order.
(2) The cushion material according to (1), wherein the release layer is a metal foil.
(3) The cushioning material according to the above (1) or (2), wherein the release layer has a thickness of 5 to 20 μm.
(4) The cushion material according to any one of (1) to (3), wherein the resin constituting the second resin layer includes a polyimide resin.
(5) Any of (1) to (4) above, wherein a difference (Tg2−Tg1) between the first glass transition temperature [Tg1] and the second glass transition temperature [Tg2] is 150 to 350 ° C. The cushion material as described in.
(6) The ratio (t1 / t2) between the thickness [t1] of the first resin layer and the thickness [t2] of the second resin layer is 0.4 to 2.7 (1) Thru | or the cushion material in any one of (5).
(7) A method for manufacturing a wiring board, comprising using the cushion material according to any one of (1) to (6).

According to the present invention, a cushioning material having excellent heat resistance and cushioning properties can be obtained even when the melting point is higher than the melting point of solder.
Moreover, according to this invention, even if it is a case where it presses above melting | fusing point of solder, the manufacturing method of the wiring board which can provide a uniform pressure to a wiring board can be provided.
Further, when the release layer is a metal foil, it is particularly excellent in workability and economy.
In addition, when the difference (Tg2−Tg1) between the first glass transition temperature [Tg1] and the second glass transition temperature [Tg2] is 150 to 350 ° C., the thermal conductivity can be particularly improved. The time required for hot pressing can be shortened.

Hereinafter, the cushioning material of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a cross-sectional view showing an example of the cushion material of the present invention.
As shown in FIG. 1, the cushion material 10 has a heat-resistant release layer 1, a first resin layer 2 having a first glass transition temperature, and a second glass transition temperature higher than the first glass transition temperature. The 2nd resin layer 3 which has is laminated | stacked.

The release layer 1 has heat resistance. Thereby, even in the press above the melting point of the solder, it has good releasability and improves workability.
Here, having heat resistance means that thermal decomposition does not easily occur, and examples include a case where the thermal decomposition temperature is 300 ° C. or higher. The pyrolysis temperature can be measured, for example, by thermogravimetric analysis.
Examples of the release layer 1 include a resin layer formed of a heat-resistant resin such as polyimide, polyamideimide, and polyetherimide, and a metal foil made of aluminum, copper, or the like. Among these, metal foil is preferable (particularly metal foil made of aluminum). Thereby, handling property can be improved. It is also economical.

  The thickness of the release layer 1 is not particularly limited, but is preferably 5 to 25 μm, and particularly preferably 10 to 20 μm. If the thickness is less than the lower limit value, the release layer 1 may break, and if the thickness exceeds the upper limit value, it may be difficult to make the pressure during pressing uniform.

  Examples of the first resin layer 2 having the first glass transition temperature include polyester resin films such as polybutylene terephthalate film and polyethylene terephthalate film, polyamide resin films such as polyamide film and polyamideimide film, polyethylene, polypropylene, and polymethyl. Examples thereof include olefin resin films such as pentene. Among these, an olefin resin film is preferable. Thereby, cushioning properties can be particularly improved.

  Although the glass transition temperature [Tg1] of resin which comprises such 1st resin layer 2 is not specifically limited, 30-70 degreeC is preferable and especially 40-60 degreeC is preferable. If the glass transition temperature [Tg1] is less than the lower limit, the amount of seepage during pressing may increase, and if it exceeds the upper limit, the cushioning property may decrease.

  Although the thickness of the 1st resin layer 2 is not specifically limited, 30-80 micrometers is preferable and especially 40-60 micrometers is preferable. If the thickness is less than the lower limit, the end face portion of the circuit may not be sufficiently embedded, and if the thickness exceeds the upper limit, the cushioning property may be lowered.

  Such a 1st resin layer 2 may contain additives, such as fillers, such as an inorganic filler and an organic filler, antioxidant, and a coloring agent.

  Examples of the second resin layer 3 having a second glass transition temperature higher than the first glass transition temperature include polyimide resin films such as polyimide resin films and polyamideimide resin films, and aramid resin films. Among these, a polyimide resin film is preferable. Thereby, it can endure the heat at the time of a press. Furthermore, a uniform smooth surface can be formed by absorbing scratches, distortions, thickness spots and the like on the hot plate and stainless steel plate.

  Although the glass transition temperature [Tg2] of resin which comprises such 2nd resin layer 3 is not specifically limited, 200-600 degreeC is preferable and 300-500 degreeC is especially preferable. If the glass transition temperature [Tg2] is less than the lower limit, the amount of seepage during pressing may increase, and if it exceeds the upper limit, the cushioning property may be reduced.

  Although the thickness of the 2nd resin layer 3 is not specifically limited, 30-80 micrometers is preferable and 40-60 micrometers is especially preferable. If the thickness is less than the lower limit value, it may be difficult to make the pressure during pressing uniform, and if the thickness exceeds the upper limit value, heat transfer to the flexible printed circuit board may be reduced.

  Such a 2nd resin layer 3 may contain additives, such as fillers, such as an inorganic filler and an organic filler, antioxidant, and a coloring agent.

Next, the relationship between the first resin layer 2 and the second resin layer 3 will be described.
The difference (Tg2−Tg1) between the first glass transition temperature [Tg1] of the resin constituting the first resin layer 2 and the second glass transition temperature [Tg2] of the resin constituting the second resin layer 3 is particularly limited. However, it is preferably 200 to 450 ° C, particularly preferably 250 to 350 ° C. If the difference is within the above range, the thermal conductivity can be improved. If the thermal conductivity can be improved, the time required for hot pressing can be shortened.

  The ratio (t1 / t2) between the thickness [t1] of the first resin layer 2 and the thickness [t2] of the second resin layer 3 is not particularly limited, but may be 0.4 to 2.7. Particularly preferred is 0.6 to 2.5. When the ratio is within the above range, the cushioning property can be particularly improved.

  The release layer 1, the first resin layer 2, and the second resin layer 3 may be bonded as they are or may be bonded via an adhesive layer. Examples of the adhesive layer include a silicone resin adhesive.

Examples of a method for manufacturing such a cushion material 10 include a method in which the release layer 1, the first resin layer 2, and the second resin layer 3 are heated and bonded together under reduced pressure.
Specifically, the release layer 1, the first resin layer 2, and the second resin layer 3 are stacked to form a cushion layer, and further, a heat-resistant film having a heat sealing layer that is slightly larger than the cushion layer Is thermocompression-bonded under reduced pressure.

Next, although the manufacturing method of a wiring board is illustrated and demonstrated about the manufacturing method of a four-layer multilayer flexible wiring board, this invention is not limited to this.
An outer layer flexible substrate, which is an outer layer having a metal foil on one side, is stacked on both sides of a double-sided flexible substrate, which is a core having a metal foil on both sides, with an adhesive interposed therebetween, and a laminate is obtained.
And the cushion material 10 mentioned above was arrange | positioned on both surfaces of a laminated body, and also it pinched | interposed with the contact plate (stainless steel mirror plate), and it heated and pressurized and obtained the multilayer flexible wiring board.
Although heating conditions are not specifically limited, 200-300 degreeC x 20-60 minutes are preferable, and 220-280 degreeC x 30-50 minutes are especially preferable.
Moreover, although pressurization conditions are not specifically limited, 0.2-0.8 MPa is preferable and 0.3-0.6 MPa is especially preferable.

EXAMPLES Next, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this.
Example 1
Manufacture of cushion material Resin composed of aluminum foil (thickness: 18 μm, manufactured by Sumikara Aluminum Foil Co., Ltd.) as the release layer and polymethylpentene (Tg1: 50 ° C., manufactured by Mitsui Chemicals) as the first resin layer A layer (thickness: 50 μm) was used, and a polyimide resin film (Tg 2: 400 ° C., thickness: 50 μm, manufactured by Kaneka Corporation) was used as the second resin layer. The release layer, the first resin layer, and the second resin layer were stacked in this order and thermocompression bonded under reduced pressure to obtain a cushion material.
The difference in glass transition temperature (Tg2−Tg1) was 350 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 1.

Manufacture of multilayer flexible wiring board A single-sided flexible printed circuit board is aligned and overlapped on both sides of a double-sided core flexible printed circuit board to be a core board with an interlayer adhesive (DBF, manufactured by Sumitomo Bakelite Co., Ltd., thickness: 16 μm). A laminate was obtained.
The above cushioning material was placed on both sides of this laminate, sandwiched between stainless mirror plates, and heated and pressurized in a vacuum press at 270 ° C. and 0.3 MPa for 60 minutes to obtain a multilayer flexible wiring board.

(Example 2)
Example 1 was performed except that the release layer of the cushion material was as follows.
Copper foil (thickness: 5 μm, manufactured by Nippon Electrolytic Co., Ltd.) was used as the release layer. The difference in glass transition temperature (Tg2−Tg1) was 350 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 1.

(Example 3)
Example 1 was performed except that the first resin layer of the cushion material was changed as follows.
As the first resin layer, a polyamide-imide resin film (manufactured by Toyobo Co., Ltd., Tg 1: 280 ° C., thickness: 50 μm) was used. The difference in glass transition temperature (Tg2−Tg1) was 120 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 1.

Example 4
Example 1 was performed except that the first resin layer of the cushion material was changed as follows.
As the first resin layer, a film of a methanol solution of polyvinyl acetate formed by a casting method (manufactured by Wako, Tg 1: 30 ° C., thickness: 50 μm) was used. The difference in glass transition temperature (Tg2−Tg1) was 370 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 1.

(Example 5)
Example 1 was performed except that the release layer of the cushion material was as follows.
As the second resin layer, a polyimide resin film (manufactured by Kaneka Corporation, Tg2: 400 ° C., thickness: 125 μm) was used. The difference in glass transition temperature (Tg2−Tg1) was 350 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 0.4.

(Example 6)
Example 1 was performed except that the release layer of the cushion material was as follows.
As the second resin layer, a polyimide resin film (manufactured by Kaneka Corporation, Tg2: 400 ° C., thickness: 18 μm) was used. The difference in glass transition temperature (Tg2−Tg1) was 350 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 2.8.

(Example 7)
The same procedure as in Example 1 was performed except that the second resin layer of the cushion material was changed as follows.
Polyethylene terephthalate (manufactured by Teijin DuPont Films, Tg 1: 70 ° C., thickness: 30 μm) was used as the second resin layer. In addition, the difference (Tg2-Tg1) of glass transition temperature was 330 degreeC. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 0.6.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the following cushioning material was used.
Kraft paper (manufactured by Oji Paper Co., Ltd., thickness 200 μm) was used as a cushioning material.

(Comparative Example 2)
Example 1 was performed except that the first resin layer and the second resin layer of the cushion material were changed as follows.
A polyimide resin film (Tg1: 400 ° C., thickness: 50 μm, manufactured by Kaneka) is used as the first resin layer, and polymethylpentene (Tg 2: 50 ° C., manufactured by Mitsui Chemicals) is used as the second resin layer. A resin layer (thickness: 50 μm) was used.
The difference in glass transition temperature (Tg2-Tg1) was -350 ° C. The ratio (t1 / t2) between the thickness t1 of the first resin layer and the thickness t2 of the second resin layer was 1.

The following evaluation was performed about the cushion material and multilayer flexible wiring board which were obtained by each Example and each comparative example. The evaluation items are shown together with the contents. The obtained results are shown in Table 1.
1. Formability of multilayer flexible wiring board Formability was evaluated by visual observation of the presence or absence of voids in the obtained 10 multilayer flexible wiring boards (size: 10 cm × 10 cm). In addition, each code | symbol is as follows.
A: There was no multilayer flexible wiring board with voids.
◯: There were 1 to 2 multilayer flexible wiring boards with voids.
(Triangle | delta): The multilayer flexible wiring board with which the void generate | occur | produced was 3-5 sheets.
X: There were 6 or more multilayer flexible wiring boards with voids.

2. Smoothness of multilayer flexible wiring board The smoothness was evaluated based on the warpage rate of the multilayer flexible wiring board in accordance with JIS C 6481 5.4. Each code is as follows.
A: Warpage rate is less than 2.0%.
○: Warpage rate is 2.0% or more and less than 2.5%.
Δ: Warpage rate is 2.5% or more and less than 3.0%.
X: Warpage rate is 3.0% or more.

3. Attachment of cushion material to multilayer flexible wiring board The adhesion of cushion material to multilayer flexible wiring board was evaluated by the area ratio (attachment rate) of the cushion material attached to the multilayer flexible wiring board (size: 10 cm × 10 cm). Each code is as follows.
A: Adhesion rate is less than 0.20% B: Adhesion rate is 0.20% or more and less than 0.25% Δ: Adhesion rate is 0.25% or more and less than 0.30% X: Adhesion rate is 0.30% or more .

4). Exuding amount of adhesive component The exuding amount of the adhesive component was evaluated with a metallographic microscope. Each code is as follows.
◎: Less than 0.5 cm ○: 0.5 cm or more and less than 1.0 cm △: 1.0 cm or more and less than 2.0 cm ×: 2.0 cm or more

As is clear from Table 1, Examples 1 to 7 were excellent in formability despite press molding at a high temperature of 270 ° C. Thereby, it was shown that the heat resistance of the cushioning material is excellent.
Moreover, Examples 1-7 were excellent also in smoothness. Thereby, it was shown that the cushioning property of the cushion material is also excellent.
Further, Examples 1 to 4 and 7 also had a small amount of cushion material attached to the multilayer flexible wiring board.
Furthermore, in Examples 1, 2, 5 and 7, the amount of the adhesive component oozing out was particularly small.

  The cushion material of the present invention can be usefully used when manufacturing a circuit board (particularly a flexible circuit board) and the like.

It is a side view which shows an example of the cushion material of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Release layer 2 1st resin layer 3 2nd resin layer 10 Cushion material

Claims (7)

A cushion material used when manufacturing a wiring board,
A release layer having heat resistance, a first resin layer having a first glass transition temperature, and a second resin layer having a second glass transition temperature higher than the first glass transition temperature are laminated in this order. Cushion material characterized by.   The cushion material according to claim 1, wherein the release layer is a metal foil.   The cushioning material according to claim 1 or 2, wherein the release layer has a thickness of 5 to 20 µm.   The cushion material according to any one of claims 1 to 3, wherein the resin constituting the second resin layer includes a polyimide resin.   The cushion material according to any one of claims 1 to 4, wherein a difference (Tg2-Tg1) between the first glass transition temperature [Tg1] and the second glass transition temperature [Tg2] is 200 to 450 ° C.   The ratio (t1 / t2) between the thickness [t1] of the first resin layer and the thickness [t2] of the second resin layer is 0.4 to 2.7. Cushion material according to crab.   A method for manufacturing a wiring board, comprising using the cushion material according to claim 1.

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