JPS6228762Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an inexpensive and highly reliable circuit board.

Conventionally, conductive foil 1 is laminated as shown in FIG.
2, 12..., a display section 10 using light emitting diodes 16, 16..., etc. is placed on one side, and an integrated circuit element 4 is placed and fixed on the other side, and wiring is provided. The display device having the section 20 can be attached to various types of equipment with a relatively small volume compared to the size of the display section 10, and there are few wirings, etc., so it is easy to handle and is used favorably. However, in order to reduce the overall cost, various problems arise because a so-called printed circuit board, in which a conductive foil is laminated on a resin base, is used instead of using ceramic or the like for the board. In particular, when the display unit 10 and the drive calculation unit 20 are located close to each other, the display unit 10 is arranged so that it can be observed from the outside of the device. It is preferable to isolate integrated circuit device 4 from the environment to prevent malfunctions. However, when the integrated circuit element 4 is covered with resin, etc., distortion and stress occur due to differences in thermal expansion coefficients between the resin, etc., the integrated circuit element 4, etc., and the resin base 11 depending on whether it is warm or cold. This is not preferable because the thin metal wires 17, 17 for wiring the element 4 may be cut or peeled off.

Therefore, if the resin base 11 is covered with a frame 13 as shown in the figure, these drawbacks can be corrected, but since the resin base 11 is originally a laminate of thin plates (pre-regs), air bubble particles tend to accumulate there. In addition, as shown in FIG. 2, the conductive foils 12, 12, . . . are subjected to repeated plating, roughening, and etching to improve wire bonding properties, so they tend to become rounded overall and have uneven surfaces. For this reason, air bubbles tend to accumulate around the conductive foils 12, 12..., so the frame 13 is
If an attempt is made to attach the adhesive 15 using adhesive 15, air bubbles tend to gather and grow while the adhesive 15 is curing. The cavities 18, 18, . . . formed at this time not only reduce the adhesive force but also allow outside air (particularly moisture) to enter the frame, resulting in defects when used for a long time.

The present invention has been devised to overcome these drawbacks, and will be described in detail below based on embodiments.

FIG. 3 is a sectional view of the main parts of the circuit board according to the embodiment of the present invention, in which 1 is a glass epoxy resin, a paper epoxy resin,
A resin base is made of paper phenol resin, baked resin, etc., and 2, 2 . . . are conductive foils made of copper or the like laminated on the resin base 1. 3 is an integrated circuit element (first
(see FIG. 4) is made of ceramic, hard resin, etc., and 5 and 5' are adhesives for sticking the frame 3 to the resin base 1.

Of these adhesives 5, 5', the adhesive 5 on the frame 3 side is an adhesive with a long gelling time, and the adhesive 5' on the resin base 1 side is an adhesive with a short gelling time. By using such adhesives 5, 5', the adhesive 5' having a short gelation time penetrates into the recessed portion of the resin base 1 first when the adhesive is cured. Although some bubbles are generated at this time, they tend to gather on the bonding surface of the two adhesives 5 and 5', and in this state, the interface of the adhesive with a short gelation time is flat, so that the adhesive 5 with a long gelation time cannot be cured. At the same time, air bubbles are expelled. An example of adhesives 5 and 5' that achieve this effect is adhesive 5 with a long gelling time.
is an epoxy resin adhesive with a thickness of 50 to 300 μm, and its gelling time is, for example, 16 minutes, while adhesive 5', which has a short gelling time, is 50 to 150 μm thick and has a gelling time of about 8 minutes. It was hot. The thickness of these adhesives is such that the adhesive 5', which has a short gelation time, has a short gelation time.
The adhesive 5 which is sufficiently thicker than m) and has a longer gelling time may have a thickness equal to or greater than that of the adhesive 5' which has a shorter gelling time. However, if the adhesive is too thick, the adhesive force will depend on the covalent bonding force of the molecules inside the adhesive, so it is better to be as thin as the Van der Waals force can be applied. On the other hand, the gelation time can be adjusted by finely adjusting the amount of inorganic filler (e.g. glass or mica), but it may also be adjusted by the standing time after adding a curing agent such as boron trifluoride monoethylamine. In this case, as long as the gelled lower layer can penetrate into the recesses etc. before the upper layer gels, the difference in gelation time should be several minutes or more. However, from the viewpoint of productivity, the former method, which does not have restrictions on coating time, is preferable.

As described above, the present invention includes a resin base, a conductive foil laminated on the resin base, an integrated circuit element placed and fixed on the conductive foil, and a cover for the integrated circuit element and attached to the resin base with adhesive. Since the circuit board is made up of a plurality of adhesive layers having different gelation times, an inexpensive resin base can be used.
Moreover, it is highly reliable because it can be completely sealed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a circuit board, FIG. 2 is a sectional view of a main part of a conventional circuit board, and FIG. 3 is a sectional view of a main part of a circuit board according to an embodiment of the present invention. 1, 11...Resin base, 2, 2...12, 12...
...Conductive foil, 3, 13... Frame, 4... Integrated circuit element, 5, 5... Adhesive.

Claims (1)

[Scope of utility model registration request] A resin base, a conductive foil laminated on the resin base,
It consists of an integrated circuit element placed and fixed on a conductive foil, and a frame that covers the integrated circuit element and is affixed to a resin base with an adhesive. A circuit board comprising a plurality of adhesive layers whose gelation time is shortened by several minutes or more.