JPS6362918B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to film substrate structures.

A well-known conventional film substrate structure, as shown in FIG. 1, is one in which copper foil 3 is adhered to both sides of a heat-resistant plastic layer 1 made of polyimide, polyacidoimide, etc. with an adhesive 2. Such a film lead structure is used as a flexible circuit board for many electronic devices, and its greatest feature is mass production using the film carrier method.

However, the reason why such a film substrate structure using polyimide or the like is not widely used is that the plastic layer 1 made of polyimide or the like supported by the copper foil ³ is extremely expensive, that is, approximately 10,000 yen per square meter.

The present invention was made in view of this point, and an object of the present invention is to realize an extremely inexpensive film substrate structure. An embodiment of the present invention will be described in detail below with reference to FIGS. 2 and 5.

The film substrate structure according to the present invention, as shown in FIG.
It is formed by adhering it to both sides with a thermosetting resin adhesive 14. The two copper foils 11 and 12 are approximately 35 μ thick copper foil used for printed circuit boards, etc., and the copper foil 1
An adhesive 14 made of a thermosetting resin such as an epoxy resin is applied to one side of each of the metal foils 1 and 12, and then pressed onto both sides of the supporting metal foil 13 to form a film. Examples of thermosetting resins include Tokkosho
It is preferable to use the one described in Publication No. 55-20394.
As the supporting metal foil 13, aluminum foil with a thickness of 50 to 100 μm is inexpensive and suitable, but copper foil may also be used. The two copper foils 11, 12 and the supporting metal foil 13 are electrically insulated from each other with an adhesive 14 having a thickness of about 15 to 30 μm, and a dielectric strength voltage of at least 600V and on average 2500V is obtained. However, since the adhesive 14 is an extremely thin layer, when press cutting is performed, there is a risk that the thin layer of the adhesive 14 will be torn at the cut surface, resulting in a short circuit.

Such a film substrate is cut into a predetermined width, for example, about 5 cm, and wound into a cartridge in units of, for example, 50 m in length as a strip film. As shown in FIG. 3, this strip-shaped film substrate 15 has index holes 17 punched out at regular intervals on both ends where the desired lead pattern 16 is not provided. Used for indexing and transporting film substrates.

The copper foil 11 on one side of the film substrate described above is selectively etched to form a desired lead pattern 16 as shown in FIG. Lead pattern 1
6 are formed electrically independently, and specifically, from the fixing pad 161 on which the semiconductor element is mounted and the electrodes 162 fixing the external terminals arranged in a DIP shape on both ends of the film substrate, to the fixing pad 161. It is composed of each electrode lead 163 extending to the vicinity. Further, since the lead pattern 16 is formed by etching, no undesirable force is applied to the lead pattern 16, thereby preventing the thin layer of the adhesive 14 from breaking and causing a short circuit. Further, the same lead pattern 16 is continuously formed at regular intervals using one of the copper foils 11 at the position determined by the index hole 17, thereby adapting to the film carrier type production process.

Further, the other copper foil 12 of the film substrate is provided with a fixing pattern 20 at a portion corresponding to the fixing pad 161, as shown in FIG. Note that if it is necessary to perform multilayer wiring, use the other copper foil 12 to connect the conductive path 2.
1 is formed and connected to the lead pattern 16 on the opposite side through-hole. The fixed pattern 20 and the conductive path 21 are formed by etching similarly to the lead pattern 16.

Etching of the two copper foils 11 and 12 on such a film substrate is carried out by screen printing a resist in the desired shape on both sides, and then continuously feeding the film substrate into a double-sided etching device, and applying the etching liquid through nozzles arranged opposite to each other. Spray on both sides and perform etching at the same time.

The film substrate on which the predetermined lead pattern 16 and back surface pattern have been formed by double-sided etching as described above is wound up into a cartridge, and then fed frame by frame from the cartridge using the index hole 17, and fixed as shown in FIG. The semiconductor element 22 and the like are fixed to the pad 161, and the electrodes of the semiconductor element 22 and the corresponding electrode leads 163 are connected with bonding thin wires. On the other hand, fixed pattern 20
After screen printing creamy solder, a metal piece 23 with good thermal conductivity for heat radiation is fixed.

At this time, the electrode lead 163 is energized to inspect the overall circuit function including the semiconductor element 22 and other circuit elements, and functional trimming can be performed if necessary. If a predetermined circuit function cannot be obtained through this inspection, the semiconductor element 22 or the like is replaced and remanufactured, or a mark is attached and the subsequent assembly process is stopped to improve the yield of the finished product. After this inspection, the semiconductor element 22 and circuit elements requiring protection are coated with silicone in a microwave oven to protect the elements and bonding thin wires.

After that, the external terminal 24 is soldered to the other end of the electrode lead 163 while still in the film form, and then the external terminal 24 is exposed and molded entirely with resin. are cut and separated into individual finished products as shown in FIG.

As detailed above, according to the present invention, an extremely inexpensive film board structure with good heat dissipation can be realized by using two copper foils and one support metal foil, and the lead pattern can be formed using copper foil. By forming a large number of them in succession, mass production can be achieved by applying the film carrier method. Furthermore, the film carrier method can be applied to circuits with high power consumption, which was considered impossible in the past, and good heat dissipation can be ensured by using metal pieces according to the power consumption.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating a conventional film substrate structure using a heat-resistant plastic layer such as polyimide, FIG. 2 is a sectional view showing a film substrate structure according to the present invention, and FIGS. 3 and 4 are illustrative of the present invention. FIG. 5 is a top view illustrating a method of assembling a semiconductor device using the film substrate of the present invention, and FIG. 5 is a sectional view of the semiconductor device using the film substrate of the present invention. Explanation of main drawing numbers 11 and 12 are copper foils, 13 is supporting metal foil, 14 is adhesive layer, 15 is film substrate, 16 is lead pattern, 17 is index hole, 22 is semiconductor element, 23 is metal piece , 24 are external terminals.

Claims (1)

[Claims] 1 A film substrate formed by adhering two copper foils to both sides of a supporting metal foil with a thermosetting resin, and etching one of the copper foils of the film substrate to form etchings at regular intervals, and at least semiconductor elements are formed on the film substrate. A conductive pattern having a fixing pad to be fixed, and a fixing pattern to which a conductive path for multilayer wiring and a metal piece for heat dissipation are fixed, which are formed by etching another copper foil of the film substrate and corresponding to the fixing pad. A film substrate structure characterized by comprising: