JPS628553Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a novel circuit structure of an improved electronic timepiece that applies a new mounting technology for semiconductor integrated circuits.

Conventionally, a semiconductor integrated circuit 1 has been packaged with leads 2 bonded to a semiconductor chip using various methods and then molded with epoxy resin, or with an outer frame made of ceramic, as shown in FIGS. 1A and 1B. It has been completed as a gift. Therefore, for connection with other functional blocks,
A circuit mounting board 3 having a wiring pattern 4 that facilitates connection with other functional blocks is separately provided, and the leads 2 of the integrated circuit 1 described above are bonded to this by soldering or the like. The circuit block thus completed is shown in FIG.

In the conventional structure described above, bonding points exist between the semiconductor chip and the leads, and between the leads and the wiring pattern on the substrate, which increases the bonding cost and complicates the process.
Therefore, the yield also decreases. Furthermore, the large number of bonding points also reduces the reliability of the circuit block. Because the minimum spacing between the terminals of the wiring pattern 4 on the board 3 is set from a manufacturing standpoint, it is also necessary to bend the leads 2 of the integrated circuit (second
figure).

Bonding with solder is particularly sensitive to heat.
Destruction of the IC chip becomes a problem. Furthermore, in the past, insufficient consideration was given to the shape of the substrate as part of the movement of watches, especially wristwatches, and the wiring pattern on it, resulting in large substrates and thick and complex circuit structures. The present invention eliminates the above-mentioned drawbacks by applying a new mounting technology, and provides a circuit structure using a low-cost, highly reliable, and compact substrate. The present invention will be explained below with reference to the drawings.

3 and 4 are explanatory diagrams of an embodiment of the present invention. Reference numeral 11 is a circuit board, which is a polyimide film in this embodiment. Copper foil is bonded to this and connections with other functional blocks or elements are made. The wiring pattern 12 is formed by photo-etching.
This embodiment is an example of a circuit block for a quartz wristwatch, and the shape of the circuit board includes a circular arc portion 11c that follows the outer shape of the wristwatch movement, a cutout portion 11d that follows the outer shape of the crystal oscillator 13, and a button-type battery (not shown). is placed so that its side surface is in contact with the small circular arc portion 17e of the circuit board 17 (similar to a conventional battery watch), a portion 11f adjacent to the step motor, and a portion 11g connecting the latter two. It has a shape whose longitudinal direction is approximately the vertical direction in FIG. 3B. In the new mounting method adopted in this invention, the polyimide board from which the circuit board is taken is a long tape with perforation holes on both sides, the same size as a 35 mm wide photographic film, as shown in Figure 3A. The direction in which the circuit board 11 is collected is such that its longitudinal direction coincides with the width direction of the polyimide tape. Each terminal on the wiring pattern is for directly connecting the integrated circuit 13, which includes the oscillation circuit, part of the motor drive circuit, and all of the frequency dividing circuit, to other elements and functional blocks. 12a is a terminal connected to the anode side of a battery power source (not shown); 12b is a terminal connected to the cathode side of the power source; 12c and 12d are terminals connected to the step motor drive coil; 12e is a terminal connected to the cathode side of the power source; Terminal 12f is a terminal connected to a switch (not shown) operated by a button on the outside of the watch case for resetting the frequency divider circuit. 12f is a terminal connected to the resistor 14 shown in phantom lines in FIG. 3. 12h is a wiring pattern that is not directly connected to the integrated circuit chip, but is fabricated on the same substrate in the same process as the wiring pattern that is directly bonded, one end of which has a resistor 14, and the other end of which has a crystal resonator 15 (shown by imaginary lines in FIG. 3), wires 12g connected to terminals on the side not connected to the integrated circuit are terminals connected to the crystal resonator 15. The respective terminals are arranged at the periphery of the circuit board adjacent to each functional block, element, etc. so as to be easily connected to them. In this embodiment, each functional block and functional element is a step motor, a resistor, and a resistor.
4. Refers to the crystal oscillator 15, power supply, reset switch, etc.

Also, the terminals 12c and 1 of the wiring for the step motor
2d are arranged close to both sides of the set screw hole 11h, but this arrangement allows the two terminals to be pressed into contact with the step motor side terminal at the same time by tightening one set screw (not shown). It is convenient because it allows for a reduction in space, number of parts, and assembly man-hours. In addition, the reset terminal 12e is placed near the button battery and near the center of the wristwatch, slightly avoiding the center where the wheel train is located, but this placement is reasonable when viewed from the circuit board side. The number of substrates to be collected from the polyimide tape is minimized by creating unnecessary protrusions.

The integrated circuit 13 is constructed by bonding a semiconductor chip 16 directly to the wiring pattern 12 on the polyimide film 11 described above, and molding this together with epoxy resin or the like.

As shown in FIG. 4, in this embodiment, the polyimide film 11 that integrally supports the integrated circuit 13 and the wiring pattern 12 is made of pins pressed into a circuit board 17 made of a thermosetting resin such as diaryl phthalate. 17a by soldering. This circuit board 17 is fixed to a main plate, which forms part of a clock movement, with screws and is incorporated into a clock. In FIG. 3, the circuit board 17 is shown with imaginary lines.

Next, the manufacturing process of this example will be explained. First, in FIG. 3, sprocket holes 11b on both sides and a chip mount hole 11a in the center are punched out in a long polyimide film 11, a thin copper foil is laminated and bonded thereon, and a wiring pattern 12 is formed by photo-etching.

After bending the copper foil over the central chip mounting hole 11a, the chip 16 is directly bonded to the tip of the copper foil, and the chip portion is then molded with epoxy resin, etc. The necessary portion of the polyimide film 11 is punched out into the shape shown in Fig. 3B (shown by imaginary lines in Fig. 3A).

As shown in the figure, the integrated circuit chip 13 is arranged so that its two sides substantially follow the longitudinal direction of the circuit board 11, and the directly bonded portions are concentrated on the other two sides. By doing this,
Each wiring pattern is arranged naturally in the longitudinal direction of the circuit board, reducing ebbs and flows, making the circuit board thin and compact. Also, considering the direction in which the circuit board is taken as mentioned above, the ends of each wiring will naturally line up on both edges of the polyimide tape, but this is because a large number of integrated circuits are successively mounted on the tape, and the outline of the circuit board When performing various functional tests before punching, the contact mechanism with the terminal of the inspection machine becomes easier.

This punched polyimide film 11 is
The hole portion is connected to the plurality of pins 17 of the circuit board 17 described above.
It is aligned with a protrusion such as a and fixed on the circuit board 17 using fixing means such as solder 17b as shown in FIG.

In this embodiment, since a flexible polyimide film is used as the circuit board, even if the circuit board 17 has a stepped portion 17c, the film and the circuit board fit together well as shown in FIG.

As described above, according to the present invention, a semiconductor chip is directly bonded to a circuit board having a wiring pattern that enables direct connection with other elements or other functional blocks to form an integral structure, and the direction of the board's pick-up relative to the polyimide tape is Since the direction of the integrated circuit, the arrangement of the wiring pattern, the terminal position, etc. with respect to both the tape and the substrate are carefully considered, the following effects are achieved.

(a) There is no need for outer bonding to connect the integrated circuit and the wiring pattern, which reduces the number of man-hours and inspections required, and also eliminates the need for connecting parts, resulting in a significant cost reduction.

(b) The reduction in the frequency of heat usage during bonding reduces the risk of damage to semiconductor integrated circuits, and since there are fewer connection points, assembly yields improve and product reliability improves.

(c) Due to the presence of a rigid circuit board, the drawbacks of a flexible board do not appear and can be considered as a completely normal watch component within the movement.

(d) The circuit boards can be made compact, and many can be cut from a standard 35 mm wide polyimide tape without waste.

(e) The wiring pattern extending from the integrated circuit chip is naturally distributed on both sides of the polyimide tape, making it convenient for inspection of the tape as it is.

(f) Wiring that connects the terminals of other elements that are not directly connected to the semiconductor chip can also be created on the same circuit board in the same process.

(g) In the case of direct bonding, the bonding point between the circuit board and the circuit board can be selected near the integrated circuit chip as shown in Figure 4, and even if the board is flexible, it can be directly bonded by impact etc. It is difficult for the bonding part to be significantly deformed and peeled off.

(h) Miniaturization of the clock shape Since a flexible substrate is used, it is possible to arrange the circuit with irregularities on the substrate, avoiding the shape of other parts of the movement, as shown in Figure 4, as necessary, so direct bonding is possible. Combined with the miniaturization of the integrated circuit chip, this is advantageous in reducing the size of the movement.

[Brief explanation of the drawing]

FIG. 1A is a plan view showing an example of a known integrated circuit, B is an elevation view of FIG. 2, and FIG. 2 is a partial plan view of a circuit board showing the integrated circuit of FIG. It is a diagram. FIG. 3A is a plan view of a polyimide film in the manufacturing process of an embodiment of the present invention;
FIG. 3B is a plan view of a circuit board showing an embodiment of the present invention, with the circuit board and other functional elements shown in imaginary lines. FIG. 4 is a cross-sectional view taken along the line -' of the circuit board showing a state in which the circuit board of FIG. 3 is assembled into the circuit board. 11... Circuit board, 12... Wiring pattern, 1
2a to 12h... each terminal of the wiring pattern, 13...
...Integrated circuit, 14...Resistor, 15...Crystal resonator, 16...Semiconductor chip, 17...Circuit board.

Claims (1)

[Scope of utility model registration request] The shape of the circuit board is surrounded by a part that roughly follows the outer shape of the wristwatch movement, a part that is close to the watch's power battery, a part that is close to the step motor, and a part that is close to the crystal oscillator. The circuit board is arranged such that a part along the circuit board and a part that connects a part near the battery and a part near the step motor are in a substantially longitudinal direction, and a copper foil is laminated on the circuit board. an integrated circuit chip disposed approximately in the center thereof, with two parallel sides substantially along the longitudinal direction, and one end of each of the two sides, at least most of which A terminal of the crystal resonator, an anode of the battery, a cathode of the battery, and two terminals of the step motor, each having the other end at the edge of the circuit board;
And the wiring pattern connected to the reset terminal,
Two ends connected to the step motor are close to each side of the set screw hole, an end connected to the reset terminal is connected to the step motor, and an end connected to the cathode of the battery. A circuit board punched from the resin tape so that the longitudinal direction is located in the width direction of the flexible resin tape, and a circuit that covers the entire surface of the circuit board. 1. A circuit structure for an electronic timepiece, characterized in that it is an integrated circuit block fixedly integrated with a base, and the integrated circuit is incorporated into a part of the wristwatch movement using the circuit block as a carrier.