JP2001040115A - Heat fusible insulating sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat fusible insulating sheet, with regard to electric insulating between a printed wiring board and an adherend, and the heat fusible heat fusibility insulating sheet, having excellent heat resistance, indicating proper flowability for adhesion of the printed wiring board and the adherend, and being possible to adhere when the sheet is heated at a low temperature of not more than 260 deg.C and besides, being possible to adhere for a relatively short time. SOLUTION: In a heat fusible insulating sheet lying between a printed-wiring board and an adherend adhering to the surface of the board, and electrically insulating and heat fusing between them, the heat fusible insulating sheet comprises a styrene resin composition having a syndiotactic structure and a thermoplastic resin compatible with the composition as principal components, the composition having contents of at least 35 wt.% and film-shaped insulator, a crystalline melt peak temperature measured when temperature is elevated with a differential scanning calorimetry being at least 260 deg.C, and a relationship between an amount of heat of crystalline melt ΔHm and an amount of heat of crystallization ΔHc generated due to the crystallization in temperature elevation satisfies equation: [(ΔHm-ΔHc)/ΔHm]<=0.6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-fusible insulating sheet for a printed wiring board which electrically insulates and heat-fuses both a printed wiring board and an object to be bonded.

[0002]

2. Description of the Related Art As a material for forming an insulating layer of a printed wiring board, a prepreg obtained by impregnating a thermosetting epoxy resin into a nonwoven fabric of glass fiber is known. Such a prepreg is commonly called a glass epoxy resin, and is sandwiched between copper foils when producing a copper-clad laminate, under a pressure of 10 to 40 kgf / cm ² and a temperature of 1
It is cured by hot press molding under the conditions of 70 to 230 ° C. and a time of about 30 to 120 minutes.

A printed circuit board made of a glass epoxy resin substrate on which a copper-clad laminate is formed as a circuit may be multi-layered by laminating a plurality of boards together. In this case, an epoxy resin-based adhesive sheet (film) is used. Is applied between two or more printed wiring boards and heated and pressed.

In some cases, a heat-resistant thermoplastic resin is used instead of a thermosetting resin such as an epoxy resin.
For example, a polyetherketone resin or a polyimide resin is known as a heat-resistant thermoplastic resin for forming an insulating layer of a printed wiring board. These resins are excellent in electrical insulation at high temperatures and are preferable materials for improving the reliability of circuit conduction of wiring boards requiring heat resistance.

[0005] By the way, when a glass epoxy resin or a heat-resistant thermoplastic resin is used as an insulating material and two or more printed wiring boards are laminated to form a multilayer, or when a metal plate is stacked on a printed wiring board to reduce heat radiation. When increasing the thickness, an epoxy resin is used as an adhesive for bonding the layers.

[0006]

However, the use of epoxy resin for bonding printed wiring boards requires 26
It is necessary to completely embed a printed circuit wired at a fine pitch by heating and pressurizing to a high temperature of 0 ° C or more to ensure insulation properties, and therefore, it takes a long time for the heating and cooling processes (heating / cooling process). There is a problem that the efficiency of the spending and bonding process is low. In addition, crystalline resins with excellent heat resistance, such as polyetherketone, cannot be adhesive unless heated to near the melting point. It is a resin that is difficult to bond.

As described above, the polyimide resin is excellent in heat resistance, chemical resistance and electrical insulation, but has a disadvantage that it has a large hygroscopicity and poor adhesion to a smooth surface. There are many technical difficulties in using it as an adhesive for boards.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a heat-fusible insulating sheet that electrically insulates both a printed wiring board and an object to be bonded and that can be heat-fused. Thermal bonding that has excellent fluidity and can be bonded with the appropriate fluidity for bonding between a printed wiring board and an object to be bonded when heated to a low temperature of 260 ° C. or less, and can be bonded in a relatively short time. To provide a conductive insulating sheet.

[0009]

In order to solve the above-mentioned problems, in the present invention, a printed wiring board is interposed between a printed wiring board and an object to be adhered to the surface of the printed wiring board to electrically insulate them from each other and to prevent heat. In a heat-fusible insulating sheet for a printed wiring board to be fused, the heat-fusible insulating sheet has a styrene-based resin composition having a syndiotactic structure, and a heat-resistant heat-resistant sheet having a compatibility with the styrene-based resin composition. A film-like insulator containing a plastic resin as a main component and having a styrene resin composition content of 35% by weight or more, and has a crystal melting peak temperature of 260 ° C. or more measured when the temperature is increased by differential scanning calorimetry. A heat-fusible insulating sheet, characterized in that the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the following formula (I): I did A.

Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6 As the above-mentioned adherend, a printed wiring board or a metal plate can be used.

[0011] The heat-fusible insulating sheet of the present invention described above comprises:
The thermoplastic resin used for bonding both the printed wiring board and the object to be bonded has a crystal melting peak temperature of 260 ° C. or higher, a heat of crystal melting ΔHm, and a rise in temperature. The relationship with the amount of heat of crystallization ΔHc generated by crystallization in the medium satisfies the relationship represented by the above formula (I). The elasticity of the plastic resin is reduced appropriately and the fine wiring pitch is filled with the thermoplastic resin, and the electrical insulation is extremely reliable. Plates can be manufactured.

In addition, since the thermoplastic resin composition appropriately promotes the crystallinity of the styrene resin having a syndiotactic structure by heating at the time of heat fusion, it has solder heat resistance to withstand 260 ° C. An insulating layer exhibiting insulating properties and having excellent mechanical strength and electrical insulating properties can be formed.

Since the thermoplastic resin composition has a high adhesive strength to a metal conductive foil, the printed wiring board having a conductive circuit formed of the conductive foil on the surface thereof and the adhered object superposed thereon are strongly bonded. Adhered to. Normally, a metal conductor foil with a roughened surface such as a copper foil with a roughened surface is used, but the adhered material having a roughened surface has a higher adhesive strength than the non-roughened material. Can be made larger.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a styrene resin having a syndiotactic structure, which is a first component constituting a heat-fusible insulating sheet, has a stereochemical structure of a syndiotactic structure, that is, a CC bond. Has a three-dimensional structure in which phenyl groups and substituted phenyl groups, which are side chains, are alternately located in opposite directions to the main chain formed from.
The content of the styrene resin is 3% of the heat-fusible insulating sheet.
5% by weight or more and a range of 35 to 70% by weight are preferable,
If it is less than 35% by weight, the solder heat resistance tends to be poor, and if it exceeds 70% by weight, the adhesion to the conductor foil tends to be poor.

[0015] Further, the second sheet constituting the heat-fusible insulating sheet can be used.
As the thermoplastic resin having compatibility with the styrene-based resin as the component, any resin capable of being uniformly dispersed at the time of melt molding may be used, and polyolefin-based, polystyrene-based, polyester-based, polyamide-based, polyphenylene ether-based, Examples include polyphenylene sulfide-based resins, but are not limited thereto. In the present invention, a modified polyphenylene ether (modified PPE) is preferably used. The content of the thermoplastic resin compatible with the styrene-based resin is preferably in the range of 30 to 65% by weight of the heat-fusible insulating sheet, and if it is less than 30% by weight, the adhesiveness to the conductive foil tends to be poor. If it exceeds 65% by weight, the solder heat resistance tends to be poor.

The heat-fusible insulating sheet may further contain a rubber-like elastic body for the purpose of improving mechanical strength in addition to the above components. The rubber-like elastic body may be a styrene-butadiene block copolymer. Coalesced (SBR), hydrogenated styrene-butadiene block copolymer (SEB), styrene-butadiene-styrene block copolymer (SBS),
Examples include, but are not limited to, hydrogenated styrene-butadiene-styrene block copolymer (SEBS). In the present invention, SEBS is preferably used among the rubbery elastic bodies. The rubber-like elastic body is preferably contained in the range of 10 to 20% by weight of the heat-fusible insulating sheet, and if it is less than 10% by weight, the effect of improving strength is small, and if it exceeds 20% by weight, heat resistance is reduced. Tend.

The thermal characteristics of the heat-fusible insulating sheet, which is an important control factor in the present invention, before the heat fusion is determined by the heat of crystal fusion Δ
Hm and heat of crystallization ΔHc generated by crystallization during heating
Is to satisfy the relationship represented by the following formula (I).

The thermal characteristic represented by the formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6 (ΔHm−ΔHc) / ΔHm is expressed by JI
The measured values of two heats of transition appearing on the DSC curve when the temperature is raised by differential scanning calorimetry according to S K 7121 and JIS K 7122, the heat of crystal fusion ΔHm (J / g) and the heat of crystallization ΔHc (J / g) Is calculated from the value of

The value of the expression (ΔHm−ΔHc) / ΔHm depends on the type and molecular weight of the raw material polymer and the compounding ratio of the composition, but depends on the molding and processing conditions of the heat-fusible insulating sheet. It has a significant effect. That is, when the film is formed into a sheet (including a film), the raw material polymer is melted and then cooled immediately, whereby the value of the above formula can be reduced. Further, these numerical values can be controlled by adjusting the heat history in each step. The heat history here refers to the temperature of the heat-fusible insulating sheet and the time during which the temperature has been reached, and the higher the temperature, the larger the numerical value tends to be.

Regarding the thermal characteristics of the heat-fusible insulating sheet before the heat-sealing, it is preferable that the value shown on the right side of the above formula (I) is as small as possible, because the adhesiveness is good. More preferably, the value on the right side of the formula (I) is 0.35 or less. Then, it is preferable that the thermal characteristics of the heat-fusible insulating sheet after the heat fusion satisfy the relationship of the following formula (II).

Formula (II): [(ΔHm−ΔHc) / ΔHm] ≧ 0.
7 When the value of the above formula (II) is as low as less than 0.7, crystallization of the thermoplastic resin composition is insufficient, and it is particularly difficult to sufficiently exhibit solder heat resistance (normally 260 ° C.). Become.

The heat-fusible insulating sheet used in the present invention can be set according to the application of the adherend without any particular limitation, and includes, for example, a film having a thickness of about 5 to 300 μm. , And a sheet exceeding 300 μm in some cases, and is generically referred to as a sheet including a film. Incidentally, the heat-fusible insulating sheet used for interlayer bonding of the multilayer printed wiring board is 25 to 300 μm.
Is preferred.

As a method for manufacturing the heat-fusible insulating sheet, a well-known manufacturing method such as an extrusion casting method using a T-die or a calendar method may be used. In addition, it is preferable to employ the extrusion casting method using a T-die from the viewpoint of film forming property and stable productivity. The molding temperature of the extrusion casting method is appropriately adjusted depending on the flow characteristics and film forming characteristics of the composition, but is generally from the melting point of the composition to 300 ° C. or less.

The thermoplastic resin composition constituting the heat-fusible insulating sheet used in the present invention may contain a resin other than the main component and other additives to such an extent that the effect of the present invention is not impaired. Specific examples of the additive include a heat stabilizer, an ultraviolet absorber, a light stabilizer, a coloring agent, a lubricant, a flame retardant, and an inorganic filler. Further, the surface of the heat-fusible insulating sheet may be subjected to embossing, corona treatment, or the like for improving handling properties or the like.

The object to be adhered in the present invention is generally assumed to be required to be adhered to the surface of a printed wiring board, for example, a metal, a resin, a ceramic, a composite material, or the like. Specific examples of the adherend include a separately prepared printed wiring board that is laminated and integrated when a multilayer printed wiring board is manufactured, or a metal plate for heat dissipation.

The printed wiring board to be bonded with the heat-fusible insulating sheet of the present invention is not particularly limited in the type of the base material and the resin of the insulating layer. It may have an insulating layer made of a resin, a glass cloth base polyimide resin, or other known materials. Among the adherends, examples of the metal type of the metal plate include aluminum, iron, copper, and zinc.
The thickness of the heat-dissipating metal plate is preferably about 0.1 to 3.0 mm, and usually about 1.0 to 1.6 mm.

It is preferable to use a metal plate having a roughened surface in order to enhance the adhesiveness. Roughening (roughening)
Examples of the method include well-known methods such as a sand blast method, a shot blast method, a dry honing method, a chemical etching method, and an electrolytic etching method. An example of use of the heat-fusible insulating sheet (embodiment) of the present invention will be described below with reference to the accompanying drawings.

The first use example shown in FIG. 1 is used as a sheet for interlayer bonding of a multilayer printed wiring board. First, as shown in FIG. A two-sided printed wiring board 2 having a layer 1 formed thereon is prepared, and a heat-fusible insulating sheet 3 made of a thermoplastic resin composition having a predetermined composition and a predetermined thermal property is sandwiched therebetween, and these are laminated by heating and pressing. Integrate.

In the insulating layer 1 of the double-sided printed wiring board 2, a double-sided through hole 4 is previously formed by laser processing, a conductive paste 5 is filled therein, and a conductor made of a roughened copper foil or the like is formed on both sides thereof. The foil is heat-sealed by a vacuum hot press machine, and a printed circuit 6 is formed by removing the unnecessary portions by a subtractive method.

Then, the heat-fusible insulating sheet 3 is overlaid on the upper surface of one double-sided printed wiring board 2, and the double-sided printed wiring board 2 prepared separately is placed and put between hot plates such as a vacuum laminating press. The layers are integrated by heating and pressing through a stainless steel plate or a cushion material as appropriate. The heat-fusible insulating sheet 3 used in this case has a temperature of 180 to 230 ° C. and a pressure of 10 to 70 kg / cm suitable for multilayering a printed wiring board having a glass epoxy resin base material as an insulating layer.
^{In step 2} , a styrene-based resin and a thermoplastic resin compatible with the styrene-based resin composition are blended and prepared so that they can be thermally fused.

In FIG. 1, one heat-fusible insulating sheet 3 is interposed between two double-sided printed wiring boards 2 formed from two double-sided copper-clad laminates to form a four-layer structure. Although the example in which the multilayer printed wiring board of the above was manufactured was shown, it is also possible to repeat the same method, or to heat and press the multilayer printed wiring board of six or more layers at once. The second usage example shown in FIG. 2 is a metal-based multilayer in which a metal plate 7 made of a copper plate is heat-sealed on one side of a double-sided printed wiring board 2 via a heat-fusible insulating sheet 3 made of a thermoplastic resin composition. It is a printed wiring board.

In any of the above usage examples, when performing heat fusion, the relationship between the heat of crystal fusion ΔHm of the thermoplastic resin composition and the heat of crystallization ΔHc generated by crystallization during heating is expressed by the formula (II). In order to satisfy the relationship shown by, for example, 230
Heat fusion at ~ 250 ° C.

Formula (II): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7 In this case, the thermoplastic resin composition is heated to a temperature near the crystal melting peak temperature (Tc) and the conductor of the printed wiring board is heated. It is possible to produce a multilayer printed wiring board having excellent heat resistance by soldering the circuits or the conductor circuit and the metal plate without fail while reliably insulating and insulating the thermoplastic resin composition.

[0034]

EXAMPLES Examples 1 to 3 of the heat-fusible insulating sheet of the present invention.
And Comparative Examples 1 and 2 for comparison with this are described below.

Example 1 A styrenic resin having a syndiotactic structure [Zarek, manufactured by Idemitsu Petrochemical Co., Ltd.] (hereinafter sometimes abbreviated as SPS) 60% by weight and modified PPE [Mitsubishi Engineering Corporation] Plastics Co., Ltd., Iupiece] 40% by weight was mixed with Mitsubishi Heavy Industries Ltd. 40 mmφ equipped with a T die.
It was extruded using a twin-screw kneading extruder (L / D = 35), immediately contacted with a cast roll having a temperature control function, and solidified to produce a heat-fusible insulating sheet having a thickness of 25 μm.

Example 2 A heat-fusible insulating sheet was manufactured in the same manner as in Example 1, except that the mixture ratio of the mixed composition was 40% by weight of SPS and 60% by weight of modified PPE.

Example 3 A heat-fusible insulating sheet was produced in the same manner as in Example 1, except that the blending ratio of the mixed composition was 30% by weight of SPS and 70% by weight of modified PPE.

Comparative Examples 1 and 2 In the same manner as in Example 1, except that the mixture ratio of the mixed composition was changed to 100% by weight of SPS (Comparative Example 1) or 100% by weight of modified PPE (Comparative Example 2). Each heat-fusible insulating sheet was manufactured.

In order to examine the physical properties of the heat-fusible insulating sheets of the above Examples and Comparative Examples, the following items (1) and (2) were measured or calculated from the measured values. These results are summarized in Table 1.

(1) Glass transition temperature (° C.), crystallization temperature (° C.), crystal melting peak temperature (° C.) Using a 10 mg sample according to JIS K7121 and heating using Perkin Elmer: DSC-7 Speed 1
Each of the above temperatures when the temperature was raised at 0 ° C./min was determined from a thermogram.

(2) (ΔHm−ΔHc) / ΔHm According to JIS K7122, 10 mg of a sample was used, and the heating rate was set to 1 using DSC-7 manufactured by Perkin Elmer.
The heat of crystal fusion ΔHm (J / g) and the heat of crystallization ΔHc (J / g) were determined from the thermogram when the temperature was raised at 0 ° C./min, and the value of the above equation was calculated.

[0042]

[Table 1]

[Manufacturing Test of Multilayer Printed Wiring Board] Thickness 5
A 0 μm glass epoxy resin substrate was subjected to a hole making process for an inner via hole with a laser, and the hole was filled with a conductive paste agent using a screen printer. After the conductive paste was sufficiently dried, an electrolytic copper foil (roughened copper foil) having a thickness of 12 μm was laminated on both sides, and pressed at 180 ° C. under a vacuum atmosphere at 760 mmHg.
° C., press pressure 30kg / cm ^2, to prepare a double-sided copper-clad laminate was heat sealed under the conditions of pressing time 60 minutes. A circuit pattern was formed on the produced double-sided copper-clad laminate by a subtractive method, and two wiring boards in which a conductive circuit was formed by etching were manufactured.

Then, as shown in FIG. 1, the thickness of 25 μm obtained in Example 1 was placed between the two double-sided printed wiring boards 2.
Heat-fusible insulating sheet 3 (Examples 1-3, Comparative Example 1,
2) sandwiching one sheet under a vacuum atmosphere at 760 mmHg at a press temperature of 240 ° C., a press pressure of 30 kg / cm ² , and a press time of 20 minutes, and thermally fused by a pin lamination method to produce a four-layer multilayer printed wiring board. . The multilayer printed wiring board was observed for delamination with a scanning electron microscope (method (3) below), and solder heat resistance was examined by the test method (4) below. Table 1
Also described in the inside.

(3) The multilayer printed wiring board is embedded in epoxy resin, and a sample for section observation is prepared by a precision cutting machine.
The cut surface was observed with a scanning electron microscope (SEM), and the presence or absence of delamination between the heat-fusible insulating sheet and the conductive circuit made of copper foil was evaluated.

(4) Solder heat resistance According to the normal solder heat resistance of JIS C6481,
After floating in a solder bath at 60 ° C. for 10 seconds with the copper foil side of the test piece in contact with the solder bath, take out from the bath and allow it to cool to room temperature, and visually observe the presence or absence of swelling or peeling,
The quality was evaluated.

The heat-fusible insulating sheet of Comparative Example 1 had a high crystallization rate at a press temperature of 180 ° C., and thus did not exhibit sufficient heat-fusibility, and a multilayer printed wiring board could not be manufactured.
The heat-fusible insulating sheet of Comparative Example 2 had a pressing temperature of 1
At 80 ° C., the adhesiveness was not sufficient, peeling was observed at a part of the interlayer between the layers, and the solder heat resistance was also insufficient. On the other hand, the heat-fusible insulating sheets of Examples 1 to 3 have excellent adhesiveness at a pressing temperature of 180 ° C. and also have excellent heat resistance such that crystallization proceeds and the crystal melting peak temperature is 260 ° C. or higher. There is also no delamination of the laminate,
It was possible to produce an excellent multilayer printed wiring board having solder heat resistance, and was excellent in adhesiveness and heat resistance.

[0048]

As described above, the heat-fusible insulating sheet of the present invention is a styrenic resin composition having a syndiotactic structure exhibiting a predetermined heat resistance, which is a heat-fusible insulating sheet for a printed wiring board. The main component is a thermoplastic resin compatible with the styrenic resin composition, and the styrenic resin has a property of appropriately promoting the crystallinity. The sheet shows fluidity suitable for bonding between the printed wiring board and the adherend when heated to a low temperature of 260 ° C. or less, and can be bonded in a relatively short time. There is an advantage that an insulating layer that exhibits endurable solder heat resistance and has excellent mechanical strength and electrical insulation can be formed.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a multilayer printed wiring board which is an example of use of an embodiment.

FIG. 2 is an enlarged sectional view of a main part of a metal-based multilayer printed wiring board which is an example of use of the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 insulating layer 2 double-sided printed wiring board 3 heat-fusible insulating sheet 4 double-sided through hole 5 conductive paste 6 printed circuit 7 metal plate

Continued on the front page F term (reference) 4F071 AA02 AA10 AA22 AA61 AA83 AF39 AF45 AF59 AH13 BA01 BB04 BB06 BC01 4J002 AA01X AC00Y AC08Y BB00X BC02W BC02X BP01Y CF00X CL00X CN01X CN02X GQ00 GQ01H02 ADD01

Claims (4)

[Claims] 1. A heat-fusible insulating sheet for a printed wiring board which is interposed between a printed wiring board and an object to be adhered to a surface thereof, electrically insulates the two and heat-bonds the two.
The heat-fusible insulating sheet has a styrene-based resin composition having a syndiotactic structure and a thermoplastic resin compatible with the styrene-based resin composition as a main component. 35% by weight or more of a film-like insulator having a crystal melting peak temperature of 260 ° C. or more measured when heated by differential scanning calorimetry, and a heat of crystal melting ΔHm, which is generated by crystallization during heating. A heat-fusible insulating sheet characterized in that the relation with the heat of crystallization ΔHc satisfies the relation represented by the following formula (I). Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6 2. The heat-fusible insulating sheet according to claim 1, wherein the thermoplastic resin compatible with the styrene resin composition is a modified polyphenylene ether resin. 3. A rubber-like elastic material is added to a film-like insulator.
3. The heat-fusible insulating sheet according to claim 1, wherein the heat-fusible insulating sheet is contained in an amount of from 20 to 20% by weight. 4. The heat-fusible insulating sheet according to claim 1, wherein the adherend is a printed wiring board or a metal plate.