JPH07135381A - Electronic device mounting board - Google Patents

Abstract

PURPOSE:To sustain strength against stress being applied from above by making an opening for mounting an electronic device in the center of a board through restriction and bending the circuit board inward into leg-shape, at a plurality of end parts, and coupling with another circuit board. CONSTITUTION:A board 100 is provided in the center with an opening 101 through restriction and an electronic device is set therein. A conductor layer extending radially from the periphery of the opening 101 toward four sides of the board is then formed on a metal plate 103 through an insulating layer 104. A lead part 105 is provided by bending at the end part of the board in order to conduct electrically with another printed board. This structure provides the electronic device mounting board with sufficient strength stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board used for mounting electronic parts, and more particularly to a board for mounting electronic parts using a metal base board.

[0002]

2. Description of the Related Art Along with the miniaturization, reduction in size, and increase in operating speed of electronic equipment in which an electronic circuit is mounted, high-density mounting and high-speed operation of the electronic circuit situation are progressing. Since high-speed operation generally increases power consumption and increases the amount of heat generated by electronic components, mounting of these electronic components used for high-speed operation requires a structure that takes heat dissipation into consideration.

As a conventional package in which electronic parts are mounted, QFP, DIP, etc. are known as typical ones. A lead frame is used as a frame for mounting electronic parts used in these packages. There is. In recent years, the number of pins of electronic parts has increased, and in lead frames mounting these multi-pin electronic parts, it is necessary to narrow the pitch of inner leads and outer leads. However, in the case of the lead frame, since the outer leads are individually projected to the outside of the package, there is a limit in securing the positional accuracy. Further, since the outer lead becomes thin, the stability of coplanarity and the decrease in strength are caused, so that there is a big problem in bending of the lead. In addition, since the inner leads are also formed individually, there is a problem in strength, and there is a limit to narrowing the pitch.
It also hinders the miniaturization of packages.

To solve these problems, the inventors of the present invention have proposed a board for mounting electronic components having a new structure in Japanese Patent Application No. 5-134728. In this structure, since the wiring portion to be the lead is formed by the PWB technique which is the wire bonding technique, it is easy to form the narrow pitch lead and the back surface is supported by the metal plate through the insulating layer. In addition, the problem of lead bending and so-called coplanarity can be greatly improved. Further, the heat generated from the electronic components is also efficiently radiated from the metal plate, which is effective as an electronic component mounting board for high-speed use, and the package can be downsized.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the electronic circuit package proposed by No. 134728, a structure in which a wiring conductor is supported by a metal plate through an insulating layer is subjected to drawing and bending using a die, and leads connected to other circuit boards are provided in the peripheral portion. The structure is arranged. This electronic circuit package is mounted on another substrate with the metal plate side facing outward after mounting electronic components, and is used in a cavity down structure. As described above, since the metal plate is arranged on the back surface, it is effective for efficient heat dissipation and coplanarity, but the problem is that it is structurally weak against stress applied from above. is there. When stress is applied from the upper part, only the outer peripheral lead portion is supported, and the lead portion is deformed or the metal portion is dented when the plate thickness is thin. Usually, as a method of mounting such an electronic circuit package on another circuit board, it is mounted on a pad portion on which a solder paste is printed while recognizing the position using a mounter. There is a possibility that the above problem may occur, and it may not always be sufficient as a board for mounting electronic parts that requires reliability and accuracy.

In view of the above problems, an object of the present invention is to provide a substrate for mounting electronic parts while maintaining its effect on heat dissipation and coplanarity, and further structurally having strength against stress applied from above, It is to provide a highly reliable electronic component mounting substrate.

[0007]

In order to solve the above-mentioned problems, the inventors of the present invention have not required a great improvement in the structure of the base material, while maintaining the heat dissipation and the stability of coplanarity, The present invention has been accomplished by earnestly studying the shape of a substrate for mounting electronic parts with higher reliability.

That is, according to the present invention, the copper foil and the metal plate are
In the metal base circuit board obtained by performing circuit processing on the copper foil surface using the metal base board laminated via the insulating layer, the electronic component mounting part is drawn at the center of the board and opened. And a plurality of end portions of the circuit board are bent inward so that the circuit processing surface faces downward, and a plurality of leads are formed in the plurality of bent portions. And a plurality of lead-shaped conductors formed in the plurality of bent portions. The electronic component mounting board is characterized in that the conductor portion is used to connect to another circuit board. 50 mm from the end of the metal substrate
A board for mounting electronic parts which is separated from each other by μm or more, and is a board for mounting electronic parts using a thermoplastic polyimide having an elongation of at least 30% or more as a layer for insulating a metal plate and a copper foil. Is.

The present invention will be described in detail below. First, referring to the attached drawings, FIG. 1 is a cross-sectional view of an electronic component mounting board according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a state in which the electronic component mounting board is mounted on another wiring board. 3 is a schematic cross-sectional view showing a state in which an electronic component is mounted, FIG. 4 is a schematic cross-sectional view showing a state in which an electronic circuit package is resin-sealed, and FIG. 5 is a flip-chip structure of the electronic component. FIG. 3 is a schematic cross-sectional view showing a state in which is mounted.
Here, 100 is an electronic component mounting substrate, 101 is an electronic component mounting portion, 102 is a wiring conductor, 103 is a metal plate, and 104.
Is an insulating layer, 105 is a lead portion, 110 is an electronic circuit package, 111 is an electronic component, 112 is a bonding wire, 113 is another printed board, and 114 is a sealing resin.

This electronic component mounting board is mounted in a so-called cavity-up shape as shown in FIG. 3, for example, as a shape to be mounted on another circuit printed board. At this time, stress is applied from the upper part by being supported by a plurality of parts, which are the electronic component mounting part formed by drawing in the center part of the substrate and the lead part formed by bending in the end part of the substrate. Can also be dispersed and have sufficient strength.

Coplanarity, which is important as a substrate for mounting electronic components, is sufficiently achieved because the structure in which the lead portion formed by bending the peripheral portion of the substrate is supported by the metal plate remains unchanged. Regarding the heat dissipation, heat is also dissipated by coming into contact with another printed board on which this electronic component mounting board is mounted via a metal plate from a portion that has been drawn as an electronic component mounting location.

In the electronic component mounting substrate of the present invention, a metal plate having a thickness of about 0.05 to 2.0 mm is used, but preferably aluminum having a thickness of about 0.1 to 1.0 mm. It is possible to use copper alloys such as white and cinnabar, copper, copper clad invar, stainless steel, iron, silicon steel, electrolytically oxidized aluminum, and the like. When the thickness of the metal plate is much smaller than this, the flatness of the surface is lowered after the final machining, the wire bondability is deteriorated at the time of mounting an electronic component, and the strength of the structure is weak, which is not preferable. Also, if the metal plate is thicker than this, there is no particular problem, but since the use of the metal plate unnecessarily increases the weight and there is no problem in simple bending, but when deep drawing is performed. Machining becomes difficult.

The insulating layer used in the present invention includes thermosetting resins such as epoxyphenol and bismaleimide, thermoplastic resins such as polyamideimide, polysulfone, polyparabanic acid and polyphenylene sulfide, and precursors of thermoplastic polyimide. A polyamic acid varnish which is obtained by heating and imidizing the varnish can also be used. Alternatively, a heat resistant organic polymer film such as polyimide,
Polyamide imide, aramid, polyether sulfone,
On both sides of each film such as polyetheretherketone,
It is also possible to use a polyamic acid varnish that is a precursor of a thermoplastic polyimide, which has been subjected to thermal imidization to form a thermoplastic adhesive layer. Further, in the case of a thermoplastic polyimide soluble in an organic solvent, a thermoplastic varnish is cast in the same manner as the above film forming method, or a film obtained by coating and drying, or an extrusion molded film or sheet of a thermoplastic polyimide. Can also be used.

Further, the metal plate used and / or
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, dried, and laminated. Furthermore, it is also possible to use the above-mentioned insulating layer materials in combination. For the purpose of further improving heat dissipation, within a range that does not impair mechanical workability such as bending,
An inorganic filler may be added to the insulating layer. Examples of these fillers include alumina, silica, silicon carbide, aluminum nitride, boron nitride and the like.

The insulating layer used in the present invention is JIS
It is optimum that the elongation at break measured by the C2318 method is 30% or more. If the elongation is less than 30%, adhesion to a metal plate may be reduced during mechanical processing such as bending and drawing, or cracks may occur in the insulating layer itself, which is not preferable. The conductor layer is relatively inexpensive and easily available,
Commercially available electrolytic copper foil, rolled copper foil and the like are used.

As a method of joining the metal plate, the insulating layer and the conductor layer to each other, there are a hot roll method, a hot press method and the like. In the embodiment of the present invention, the conductor layer has a single-layer structure.
A multi-layered structure may be used if necessary. As a method for forming a multi-layer structure, there are, for example, a build-up method and a laminating method. The build-up method is a method of sequentially laminating an insulating layer and a conductor layer on a metal plate. On the other hand, the laminating method is to form a sheet in which only an insulating layer and a conductor layer are laminated, and the conductor layer is exposed on both sides of the sheet. By joining, a multilayer structure is realized. On both sides of glass epoxy,
You may use the multilayer circuit board formed using the copper clad laminated board to which the copper foil was stuck. In that case, it is attached to a flat part other than the bent part and the narrowed part and used as a multilayer circuit.

In the case of a multi-layer structure, a through hole is generally provided for the purpose of interlayer connection. As a method therefor, a drill, laser light from an excimer laser, or etching with an alkaline solution when the insulating layer is polyimide is used. Can be formed. As a method of electrically connecting the conductor layers through the through holes, plating, solder, conductive paste, etc., which are generally used in the ordinary method for manufacturing a printed wiring board, can be used. It is also possible to connect by wire bonding.

The drawing and bending mechanical workings of the present invention can be carried out by press working using a mold which is a conventional method. The conductor may be resin-coated on the surface of the mold for protection during the drawing process, or the mold may be provided with a concave shape in accordance with the shape of the pattern. In deep drawing and bending with a small radius of curvature, processing such as application of heat or processing such as swelling the insulating layer with a solvent or the like may be performed.

The lead portion used for connection with another printed board may have various structures, but in order to improve the connection reliability and prevent damage to the insulating layer and the wiring conductor, It is desirable to process the radius of curvature in the range of about 0.1 to 5.0. In the examples described later, an example of 0.5 mm is shown. In addition, what is important in the lead portion is that the wiring conductor used as the lead is formed sufficiently longer than the plate edge, preferably 50 μm or more. This distance is not long enough, for example 50 μm
When it is within the range, a short circuit between the lead and the metal plate may occur due to the wraparound of the solder when it is mounted on another printed board, which is not preferable. The corner forming the bottom of the electronic component mounting portion has an inner radius of curvature of 0.1 to 10 mm.
Is 0.5 mm in the embodiment of the present invention.
And

Next, an example of a specific mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the configuration of an embodiment of the package of the present invention, and FIG. 2 is a perspective view thereof. This electronic component mounting substrate 100
Has one circuit-processed conductor layer 102 (wiring conductor). After the circuit pattern is formed, it is formed by bending and drawing. At the center of the electronic component mounting substrate 100, there is an opening 101 formed by drawing, and an electronic component is mounted in this recess. The package is preferably formed by processing into a box shape having an opening surface. A conductor layer 102 is radially formed on the metal plate 103 via the insulating layer 104 from the peripheral edge of the opening surface to the four ends of the substrate.

A lead portion 105 formed by bending is provided at the end of the substrate, and the lead portion 105 is used to electrically connect to another printed substrate. Here, for example, a copper plate having a thickness of 0.2 mm is used as the metal plate 103, and here, LARK-TPI manufactured by Mitsui Toatsu Chemicals, which is a thermoplastic polyimide, is used as the insulating layer 104, and the thickness of the insulating layer is here. It was set to 20 μm. Here, the wiring conductor 102 is 1
A rolled copper foil of 8 μm was used. The metal plate 103 and the copper foil were laminated using a heat press via the insulating layer 104 to form a metal base substrate.

Next, the wiring conductor was subjected to circuit processing using a general printed wiring board processing technique to form a wiring conductor 102. After that, mechanical processing using a die is performed, and first, the electronic component mounting portion 101 is formed by drawing, and then the lead portion 105 at the end portion of the substrate is sequentially formed. In the electronic component mounting substrate 100 thus formed, the flatness of the lead portions on the four sides is preferably 50 μm or less, and the opening portion is formed in the central portion of the substrate by drawing, By having the lead portions formed by bending on the four sides, the electronic component mounting board had no warp and had good stability.

FIG. 3 is a schematic sectional view showing an electronic circuit package 110 obtained by mounting an electronic component 111 on the electronic component mounting board 100. The electronic component 111 is electrically connected to the wiring conductor 102 by wire bonding 112. FIG. 4 is a schematic cross-sectional view showing a product obtained by resin-sealing an electronic circuit package. Although one bare chip is mounted as an electronic component on the electronic circuit package 110 shown in FIG. 3, it is also possible to mount a plurality of bare chips and surface mount type chip components according to the purpose.

FIG. 5 is a schematic cross-sectional view showing a structure in which the wiring conductor is formed by drawing the electronic component mounting portion and extended to the inside of the recess. In such a case, the bare chip can be mounted in a flip chip structure, and can be thinner than 110 mounted by wire bonding.

[0025]

The effects of the present invention include the following as a substrate for mounting electronic components. (1) The coplanarity stability of the lead is improved because it is supported by the metal plate including the lead portion. (2) The heat generated from the electronic component via the metal plate is efficiently dissipated from the ground plane with another printed board. (3) Since the electronic component mounting portion has a concave shape formed by drawing, it is easy to perform potting resin sealing after mounting the electronic component. (4) The structural strength of the electronic component mounting substrate is improved, and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electronic component mounting board according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a state where the electronic component mounting board is mounted on another wiring board.

FIG. 3 is a schematic cross-sectional view showing a state of an electronic circuit package on which electronic components are mounted.

FIG. 4 is a schematic cross-sectional view showing a state in which an electronic circuit package is resin-sealed.

FIG. 5 is a schematic cross-sectional view showing an electronic circuit package state in which electronic components are mounted in a flip chip structure.

[Explanation of symbols]

 100 Electronic Component Mounting Substrate 101 Electronic Component Mounting Part 102 Wiring Conductor 103 Metal Plate 104 Insulating Layer 105 Lead Part 110 Electronic Circuit Package 111 Electronic Component 112 Bonding Wire 113 Other Printed Board 114 Sealing Resin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsumi Hoshino 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] 1. A metal base circuit board obtained by subjecting a copper foil surface to circuit processing using a metal base board in which a copper foil and a metal plate are laminated via an insulating layer, in the center of the board. The electronic component mounting portion is formed into an opening shape by drawing the portion, and a plurality of end portions of the circuit board are bent inward so that the circuit processing surface faces downward, and at the same time, An electronic component mounting board, characterized in that a plurality of lead-shaped conductor portions in a plurality of bent portions are used to enable connection with another circuit board. 2. The tips of a plurality of lead-shaped conductors formed on the plurality of bent portions are 50 μm from the outermost end of the metal substrate.
The electronic component mounting substrate according to claim 1, wherein the substrates are formed separately from each other. 3. The electronic component mounting substrate according to claim 1, wherein a thermoplastic polyimide having an elongation of at least 30% is used as a layer for insulating the metal plate and the copper foil.