JPH08279684A - Metal base multilayered circuit board - Google Patents

Abstract

PURPOSE: To improve reliability of resistance to heat, by using thermoplastic polyimide for multilayer lamination wherein the glass transition temperature is higher than that of thermoplastic polyimide for bonding a multilayered flexible wiring board to a metal plate. CONSTITUTION: A four-layered flexible board is bonded to the single surface of a metal board 100, via thermosetting polylmide 201. Wiring conductors 301-304 are formed by circuit-working a double-sided FCL board, and interlayer-coupled by insulator wherein thermosetting polyimide 203 is formed on both surfaces of a heat-resisting film 202. Through holes 401, 402 are formed for continuity. The thermosetting polyimide 203 whose glass transition temperature is higher than that of the thermosettting polyimide 201 for bonding the metal plate to the multilayered flexible wiring board is used between layers. Thereby through hole breakdown and disconnection which are to be generated in the bonding process can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed board used for mounting electronic parts, and more particularly to a metal-based multi-layer wiring board having a multi-layer wiring structure formed on a metal base.

[0002]

2. Description of the Related Art Wiring boards are becoming denser, thinner, smaller and smaller, and operating speeds of electronic equipment mounted on the wiring boards are becoming higher. When electronic parts are mounted on this wiring board with high density and operate at high speed, power consumption generally increases and the amount of heat generated by electronic circuits increases. Therefore, heat dissipation is required for high speed operation and high density mounting. Considered structure is required. Conventionally, as a wiring board material, a resin-based printed wiring board typified by glass epoxy has been used from a cost performance standpoint. However, as mentioned above, due to the recent development of packaging technology,
Characteristics such as heat dissipation, mechanical strength, shielding, and reliability have been demanded for wiring boards on which electronic components are mounted. In response to these demands, attention has been paid to a metal-based wiring board using a metal such as aluminum, copper, and stainless as a base material. The metal base substrate is characterized by good heat dissipation, mechanical strength, dimensional stability and the like.

[0003] As a method of multi-layer wiring of these metal base boards, a method of sticking a multi-layer circuit board of a glass epoxy board or a multi-layer flexible board of polyimide base to a metal base with an epoxy resin adhesive, or an epoxy resin insulating layer As the above, a build-up method is known in which a plurality of conductor layers are formed.

However, in recent years, heat resistance has been required in applications where the ambient temperature of use is relatively high, such as around the engine of an automobile. There is a limit, and the heat resistance of the adhesive is insufficient even in the method of sticking the polyimide multilayer wiring board to the metal substrate with the adhesive such as epoxy resin,
There was a problem in heat resistance and heat reliability.

[0005]

As described above, as a problem of the prior art, a multilayer wiring board is formed on a metal plate, and after mounting electronic parts, reliability in an environment where the operating temperature is relatively high is high. , Inadequate. Generally, when an epoxy resin is used for an insulating layer and an adhesive layer, the usable temperature range of the epoxy resin is 150 ° C. or lower due to the resin characteristics. In view of the above problems, it is an object of the present invention to obtain a metal-based multi-layer wiring board that makes use of the characteristics of heat dissipation, mechanical strength, and dimensional stability of a metal-based board, and can further improve reliability with respect to heat resistance. To do.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a result, carried out a multilayer flexible structure having a through hole in which interlayer adhesion was performed using a thermoplastic polyimide. The object is achieved by joining the wiring board to the metal base by using the thermoplastic polyimide used for adhesion between layers of the flexible board and the thermoplastic polyimide having different glass transition temperatures (Tg). I found things and completed the present invention.

That is, according to the present invention, (1) a flexible multilayer wiring board having through holes is bonded to a metal plate and has a multilayer wiring layer on one side or both sides.
In a metal-based multilayer wiring board, the glass transition temperature of the thermoplastic polyimide used for multilayer lamination is higher than the glass transition temperature of the thermoplastic polyimide for joining the multilayer flexible wiring board to the metal plate. A metal-based multi-layer wiring board, characterized by being laminated, and (2) using polyimide as an insulating layer,
Glass transition of thermoplastic polyimide used for multi-layer lamination in a metal-based multi-layer wiring board having through-holes, an all-polyimide multi-layer flexible wiring board bonded to a metal plate, and having a multi-layer wiring layer on one side or both sides Temperature is for joining a multilayer flexible wiring board to a metal plate, using a thermoplastic polyimide higher than the glass transition temperature of the thermoplastic polyimide, characterized by laminating, a metal-based multilayer wiring board, also, (3)
The glass transition temperature of the thermoplastic polyimide used for the multi-layer lamination is 20 than the glass transition temperature of the thermoplastic polyimide for joining the multi-layer flexible wiring board to the metal plate.
A thermoplastic resin which is a metal-based multilayer wiring board according to (1) or (2), characterized by using a material having a temperature higher than or equal to ℃, and (4) used for bonding a multilayer flexible board to a metal plate. The glass transition temperature of polyimide is 1
(1) to characterized by using one having a temperature of 60 ° C. or higher.
The present invention relates to the metal-based multilayer wiring board according to any one of (3).

The gist of the present invention is, in short, that a multilayer flexible wiring board having through holes, in which a polymer having high heat resistance is used as an insulating layer, preferably a polymer such as polyimide is used as an insulating layer, is bonded to a metal plate. In a metal-based multi-layer wiring board having one or both sides of a multi-layer wiring layer, the glass transition temperature of the thermoplastic polyimide used for (adhesive layer of) the multi-layer is One of the major characteristics is to use one having a glass transition temperature higher than that of the thermoplastic polyimide, preferably 20 ° C. or higher, for bonding (used as an adhesive layer). When the wiring board is joined to a metal plate, the required temperature is reduced, so that the heat Of a highly reliable metal-based multi-layer wiring board, which prevents the breakage of a through-hole for the purpose of electrical conduction between layers and disconnection caused by the softening of the conductive polyimide again. It is in.

[0009] Further, preferably, an adhesive used for joining all layers of a multilayer flexible wiring board having a heat-resistant polymer such as polyimide as an insulating layer, or an adhesive used for joining the multilayer flexible wiring board to a metal plate. By using a thermoplastic polyimide having a glass transition temperature of 160 ° C. or higher as the agent, the heat dissipation of the metal-based multilayer wiring board
To further improve heat resistance due to features such as mechanical strength,
It is a feature. Hereinafter, the present invention will be described in detail.

First, referring to the attached drawings, FIG.
FIG. 3 is a cross-sectional view of a metal-based single-sided multilayer wiring board showing an example of the present invention (formed by joining two double-sided FCLs). On one surface of the metal substrate 100, the thermoplastic polyimide 20
The four layers of flexible substrates are bonded to each other through 1. The wiring conductors 301, 302, 303, 304 are formed by processing a circuit on a double-sided FCL substrate,
On both sides of No. 02, interlayer bonding is performed with an insulator having a thermoplastic polyimide 203 formed thereon. In addition, the wiring conductor 301,
Through holes 401 and 402 are formed for the purpose of electrically connecting 302, 303 and 304.

FIG. 2 is a cross-sectional view of a metal-based single-sided multilayer wiring board showing an example of the present invention (formed by joining copper foils on both sides of a double-sided FCL). Wiring conductors 305, 306
Is formed by processing a circuit on a double-sided FCL substrate,
7 and 308 are thermoplastic polyimide 204 on one side of the copper foil.
The single-sided copper flexible substrate on which the
5, 306 are joined to both surfaces and processed by a circuit. Then, the heat resistant film 202 is formed on the metal plate 100.
Adhesive sheets having thermoplastic polyimide 203 formed on both surfaces are joined together.

Here, in FIG. 1, the glass transition temperature of the thermoplastic polyimide 203 used for multi-layer stacking (joining between layers) of the multi-layer flexible wiring board is such that the thermoplastic resin for joining the metal plate and the multi-layer flexible wiring board is thermoplastic. A material having a glass transition temperature higher than that of the polyimide 201 is used.
This is effective in preventing through-hole breakage and wire breakage that occur in the bonding process, and enables a highly reliable metal-based multilayer wiring board.

The metal plate 100 used in this metal-based multilayer wiring board is not particularly limited, but a material having a thickness of about 0.05 to 3.0 mm is used, and preferably 0.1. ~ 1.0 mm aluminum, copper alloy such as nickel silver and cinnamon, copper, copper clad invar,
Stainless steel, iron, silicon steel, electrolytically oxidized aluminum, or the like can be used. The thickness and material can be selected according to the purposes such as heat radiation, mechanical strength, dimensional stability due to thermal expansion, and oxidation resistance. It is also possible to use a metal plate which has been subjected to a surface treatment such as mechanical roughening treatment, chromate treatment or electrolytic roughening treatment, which is effective for adhesion to the thermoplastic polyimide, on the surface of the metal.

As a method for producing a multilayer flexible wiring board used in the present invention, first, a flexible board is prepared by circuit-processing a plurality of double-sided FCL boards in which copper foils are bonded to both surfaces of a heat-resistant insulating film. A film of a thermoplastic polyimide, or both sides of a heat-resistant film such as polyimide, obtained by coating and drying a thermoplastic polyimide varnish, using a film, a plurality of flexible wiring board processed circuit, joined how to,
Alternatively, the circuit-processed, both sides of the flexible substrate, one side of the copper foil is coated and dried with a thermoplastic polyimide varnish, the obtained single-sided copper foil flexible substrate, the double-sided circuit board of the flexible substrate, both sides And a method of manufacturing a multilayer flexible wiring board.

As the heat resistant film 202, for example, polyimide, polyamideimide, aramid, polyether sulfone, polyether ether ketone, etc. can be used. As a method for forming a thermoplastic polyimide layer used for bonding, on both surfaces of the film, a polyamic acid varnish that is a precursor of a thermoplastic polyimide, a product obtained by heating and imidizing can also be used, and is also soluble in an organic solvent. In the case of such a thermoplastic polyimide, a film obtained by casting or coating and drying a thermoplastic varnish in the same manner as in the above-mentioned film forming method, or an extrusion molded film or sheet of a thermoplastic polyimide can also be used. Further, a polyimide acid varnish or a thermoplastic polyimide may be applied to the back surface of the copper foil used for forming the conductor layer to be used and dried to form it.

As a method for forming a multilayer flexible substrate by joining layers through a thermoplastic polyimide, a known method such as a heat laminating method using a heat roll or a hot press can be used. In this case, the heating conditions are preferably set to a temperature higher than the glass transition temperature of the thermoplastic polyimide used. More preferably, a setting higher than the glass transition temperature by about 10 ° C. or more is desired. The pressurizing condition is 20 to 100 kg / c
A range of m ² is used.

After that, through-holes for circuit processing of outer layers and electrical connection between the multi-layer circuits of the multi-layer flexible substrate in which the joining between the layers is completed are usually formed by the technique of the printed wiring board, and the multi-layer flexible wiring is formed. The board is completed.

Next, using the film obtained by coating the multilayer flexible wiring board on a target metal plate with thermoplastic polyimide varnish on both surfaces of a heat-resistant film such as polyimide, or by drying, Bonding is performed using a thermoplastic polyimide film obtained by extrusion molding or the like. As a method for joining the metal plate and the multilayer flexible wiring board, a known method such as a heat laminating method using a heat roll or a hot press can be similarly used. In this case, the heating conditions are preferably set to a temperature higher than the glass transition temperature of the thermoplastic polyimide used. More preferably, it is desired to set the temperature higher than the glass transition temperature by about 10 ° C. or more. As the pressurizing condition, a range of ^{20 to} 100 kg / cm ² is used. This completes the metal-based multilayer wiring board.

The thermoplastic polyimide in the present invention is a polymer having an imide structure in the main chain and has a glass transition temperature of 160 ° C. or higher. It means that the elastic modulus decreases. When the glass transition temperature is less than 160 ° C, the heat resistance of the finished metal-based multilayer wiring board is insufficient, which is not preferable. The upper limit of the glass transition temperature of the thermoplastic polyimide is not particularly limited, but considering the efficiency of the heating lamination step, up to about 350 ° C,
Thermoplastic polyimide is preferred.

What is important in the present invention is that the thermoplastic polyimide used for the interlayer bonding of the multilayer flexible substrate and the thermoplastic polyimide used for bonding the multilayer flexible wiring substrate to the metal plate have different glass transition temperatures. Yes, the glass transition temperature of the former is higher than that of the latter. Preferably,
The glass transition temperature of the thermoplastic polyimide used for interlayer bonding of the multilayer flexible substrate is 20 ° C. or higher than the glass transition temperature of the thermoplastic polyimide used for bonding the multilayer flexible substrate to the metal plate. It is desirable to use a plastic polyimide.

Thus, when the thermoplastic polyimide is used to bond the multilayer flexible substrate to the metal plate, the elastic modulus of the thermoplastic polyimide used for bonding the multilayer flexible wiring substrate is not significantly reduced. Therefore, the through-holes provided in the multilayer flexible wiring board for the purpose of electrical conduction between the layers are broken or broken due to a large decrease in elastic modulus of the thermoplastic polyimide used for joining the layers of the multilayer flexible wiring board. Can be prevented
A highly reliable metal-based multilayer wiring board can be manufactured. When the difference between the glass transition temperature of the thermoplastic polyimide used for interlayer bonding of the multilayer flexible substrate and the glass transition temperature of the thermoplastic polyimide used for bonding the multilayer flexible substrate to the metal plate is less than 20 ° C. In the heating and joining process for joining the multi-layer flexible substrate to the metal plate, breakage or disconnection of a through hole formed for the purpose of electrical conduction between layers may occur, which is not preferable.

[0022]

Embodiments of the present invention will now be described with reference to the drawings.
explain. [Embodiment 1] Referring to FIG. 1, wiring conductors 301, 30
2, 303 and 304 are made of electrolytic copper foil, double-sided FCL
Circuit processing of the board (Mitsui Toatsu Chemical Neoflex)
Formed, heat-resistant film (Kanefuchi Chemical Co., Ltd. Apical A
H) Thermoplastic with glass transition temperature of 210 ℃ on both sides of 202
-Resistant polyimide (PI-A manufactured by Mitsui Toatsu Chemicals) 203 is applied.
Dry-formed, film-to-layer thermal bonded. Well
In addition, the wiring conductors 301, 302, 303, 304 are electrically connected.
Through-holes 401 and 402 are formed
Has been established. Where the interlayer heat of the multilayer flexible substrate
Joining is performed by the pin laminating method, and under vacuum
Heating temperature 220 ℃, pressure 40kg / cm ²One hour
Heat-bonded with less.

Next, on one surface of the aluminum metal plate 100, a four-layer flexible substrate is formed by thermal bonding via a thermoplastic polyimide (PI-Ah manufactured by Mitsui Toatsu Chemicals) 201 having a glass transition temperature of 190 ° C. . The conditions for joining the multilayer flexible wiring board to the aluminum metal plate are heating temperature of 210 ° C. and pressure of 40 kg / c under vacuum.
Thermal bonding was performed with a m ² press for 1 hour. This metal-based multi-layer wiring board is used under the condition of temperature of -65 ° C to + 170 ° C.
A temperature cycle test was performed 00 times, but no change was observed in the conductivity of the through holes, and the heat resistance reliability was good.

[Embodiment 2] Referring to FIG. 2, the wiring conductors 305 and 306 are formed by circuit-processing a double-sided FCL substrate (Neoflex manufactured by Mitsui Toatsu Kagaku).
308 is a rolled copper foil (BHY-02 manufactured by Japan Energy)
BT) has a glass transition temperature of 230 ° C. and a thermoplastic polyimide (LAC-TPI made by Mitsui Toatsu Co., Ltd.) 204 formed on one side thereof.
It is formed by being joined to both sides of 06 and processed into a circuit.
Here, in the interlayer thermal bonding of the multilayer flexible substrate, alignment is performed by a pin laminating method, and a heating temperature of 250 is set under vacuum.
Thermal bonding was performed by pressing at a temperature of 40 ° C. and a pressure of 40 kg / cm ² for 1 hour.

Then, a glass transition temperature of 210 is applied to both surfaces of the heat-resistant film (apical AH manufactured by Kanegafuchi Chemical Co., Ltd.).
℃ thermoplastic polyimide (Mitsui Toatsu Chemicals PI-A) 2
03, the metal sheet 100 is formed by using the adhesive sheet.
And the multilayer flexible wiring board. The conditions for joining the multilayer flexible wiring board to the aluminum metal plate are heating temperature of 210 ° C. and pressure of 40 kg under vacuum.
/ Cm ² , and heat bonded by pressing for 1 hour. This metal-based multilayer wiring board was also subjected to a temperature cycle test of 200 times under the condition of a temperature of −65 ° C. to + 170 ° C. However, no change was observed in the conductivity of the through hole, and the heat resistance reliability was the same. It was good.

[Comparative Example 1] The structure described in Example 1 and FIG.
First of all, in the bonding,
In the same manner as in Example 1, a glass transition temperature of 210 ° C.
Coating and drying with plastic polyimide (PI-A manufactured by Mitsui Toatsu Chemicals)
The formed film is thermally bonded between layers. here
Then, the interlayer thermal bonding of the multilayer flexible substrate is the same as in Example 1.
Similarly, perform alignment using the pin-lamination method and apply under vacuum.
Heat temperature 220 ℃, pressure 40kg / cm ²1 hour pre
It was heat-bonded. Next, the multilayer flexible circuit board is
As a method of heat bonding to a aluminum metal plate, a multilayer flexible
Glass transition temperature of 210 used for interlayer bonding of the sible substrate
℃ thermoplastic polyimide (Mitsui Toatsu Chemicals PI-A)
Joined through. Aluminum multilayer wiring board
The heating temperature under vacuum is also used as the condition for joining the aluminum metal plate.
220 ℃, pressure 40kg / cm²Under the same conditions for 1 hour
Heat-bonded with a press.

In this metal-based multilayer wiring board, the electrical resistance of the through hole was slightly higher than that of the example. As a result of observing the cross-section of the through-hole part, the through-hole part was used for interlayer bonding of the multilayer flexible substrate,
Cracks were observed, which are believed to be caused by the softening of the thermoplastic polyimide. Further, the temperature is -65 ° C to +1
A temperature cycle test was conducted 200 times under the condition of 70 ° C., but the electric resistance value of the through hole portion further increased,
The result is insufficient reliability.

[0028]

According to the present invention, as a metal-based multilayer wiring board, a metal-based multilayer wiring board having improved heat resistance and heat resistance reliability in addition to features such as heat dissipation and mechanical strength can be obtained. . Further, by using a thermoplastic polyimide used for interlayer bonding as a thermoplastic polyimide having a different glass transition temperature, a large decrease in elastic modulus of the thermoplastic polyimide used for bonding between layers of a multilayer flexible wiring board having a through hole is caused. It is possible to obtain a highly reliable metal-based multilayer wiring board that can prevent breakage and disconnection.

[Brief description of drawings]

FIG. 1 is a sectional view of a metal-based multilayer wiring board showing an example of the present invention (formed by joining two double-sided FCLs).

FIG. 2 is a cross-sectional view of a metal-based multilayer wiring board showing an example of the present invention (one formed by joining copper foils on both sides of a double-sided FCL).

[Explanation of symbols]

 100 metal plate 201 thermoplastic polyimide layer (Tg 190 ° C) 202 heat resistant film layer 203 thermoplastic polyimide layer (Tg 210 ° C) 204 thermoplastic polyimide layer (Tg 230 ° C) 301, 302, 303, 304 conductor layer 305, 306, 307, 308 Conductor layers 401, 402 Through holes

Front page continuation (72) Inventor Hikaru Kanemitsu 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Kunihiro Nagamine 1190, Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Chem., Ltd.

Claims (4)

[Claims] 1. A thermoplastic resin used for multi-layer lamination in a metal-based multi-layer wiring board, wherein a flexible multi-layer wiring board having through holes is bonded to a metal plate and has multi-layer wiring layers on one side or both sides. A metal-based multilayer wiring board, characterized by being laminated using a thermoplastic polyimide having a glass transition temperature of polyimide higher than that of thermoplastic polyimide for joining the multilayer flexible wiring board to a metal plate. 2. A metal-based multi-layer wiring board having a through hole, which has polyimide as an insulating layer, and which is bonded to a metal plate, and which has a multi-layer wiring layer on one side or both sides. The glass transition temperature of the thermoplastic polyimide used in the multilayer lamination, for joining the multilayer flexible wiring substrate to the metal plate, using a thermoplastic polyimide higher than the glass transition temperature of the thermoplastic polyimide, characterized by laminating To do
Metal-based multilayer wiring board. 3. A glass transition temperature of a thermoplastic polyimide used for multi-layer lamination is 20 ° C. or more higher than a glass transition temperature of a thermoplastic polyimide for bonding a multi-layer flexible wiring board to a metal plate. The metal-based multilayer wiring board according to claim 1 or 2, which is characterized in that. 4. A thermoplastic polyimide having a glass transition temperature of 160 ° C. or higher, which is used for bonding a multilayer flexible substrate to a metal plate, is used. Metal-based multilayer wiring board.