JPH0729514Y2 - Electronic timepiece circuit board and electronic timepiece - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a layout of a wiring pattern for a crystal unit of a circuit board for an electronic timepiece.

[Prior Art] In a conventional electronic timepiece circuit board, two wiring patterns for connecting the IC chip 1 and the crystal unit 2 are connected to each other as shown in FIG. They were arranged almost parallel to each other and there was no space between both patterns.

[Problems to be solved by the invention] However, in the above-mentioned circuit board, since the wiring patterns for the crystal unit are adjacent to each other, it is necessary to adhere the copper foil when forming the wiring pattern on the circuit board. The adhesive and the molding agent to enhance the fixing force of the IC chip to the circuit board become a dielectric, and a relatively large stray capacitance is formed between both wiring patterns. However, there is a problem that the rate of change in the rate due to is large. The rate of change at this time varies depending on the length of the wiring pattern, but when the humidity changes from 40% to 90% at a temperature of 20 ° C, it will be about 0.05 to 0.07 sec / day, which is high for a high-accuracy watch with an annual difference of 10 seconds. Becomes a fatal value.

The present invention is intended to solve the above-mentioned problems, and its purpose is to suppress the rate change caused by the change of the stray capacitance value due to the change of humidity and increase the accuracy guarantee rate of a high-precision watch such as 10 seconds per year. Especially.

[Means for Solving the Problem] The circuit board for an electronic timepiece according to the present invention has one of two wiring patterns conductively connected to a crystal unit, one of which is formed on the substrate and the other of which is separated from the substrate and overlaid. It is hung.

[Operation] According to the above configuration of the present invention, by forming one of the two wiring patterns for the crystal unit on the substrate and overhanging the other away from the substrate, the two wiring patterns are formed. Since air is present between the two, it is possible to reduce the stray capacitance between them, and as a result, it is possible to reduce the rate change amount due to the change in the stray capacitance value due to the humidity change. Further, by wiring one of them on the substrate, the rigidity of the circuit board between the crystal unit and the wiring connection destination can be increased, and the displacement of the mounting position of the crystal unit can be reduced. Moreover, since one wiring pattern is formed and fixed on the circuit board as well as the positional displacement of the crystal unit is reduced, it is possible to reduce the change in the distance between the wiring patterns when the circuit board is mounted. It is also possible to reduce variations in wiring capacitance due to changes in distance.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples. A plan view of a circuit block for an analog watch according to an embodiment of the present invention is shown in FIG. 1, and a sectional view thereof is shown in FIG. In FIGS. 1 and 2, reference numeral 1 is a CMOS-IC for an analog electronic timepiece having a function of compensating for the secondary temperature characteristic of the crystal unit 2 based on the information of the semiconductor temperature sensor incorporated in the 1a section. Chips, 2 is 3
A tuning fork crystal unit that oscillates at 2768Hz and has a secondary temperature characteristic, 3 is a circuit board having a wiring pattern formed by etching a copper foil adhered to a flexible tape, and IC chip 1 is face-down bonding. The crystal unit 2 is mounted on the circuit board 3 by soldering. Further, in order to increase the fixing force of the IC chip 1 to the circuit board 3, an epoxy type molding compound 4 is poured from the hole 3d. Floating capacitance is formed between the wiring patterns of the circuit board 3 by an adhesive for adhering a copper foil or a molding agent 4 protruding from the IC chip mounting portion.

As shown in FIG. 1, in the circuit board 3 of the present embodiment, of the two wiring patterns 3a and 3b for the crystal unit, 3a is made to overhang substantially along the outer shape of the circuit board 3. ing. Therefore, the stray capacitance value formed by the adhesive or the molding agent between both patterns becomes small, and the rate change due to the change in the stray capacitance value due to the humidity change becomes small.

FIG. 3 shows the humidity characteristics of the rate of the circuit block A of FIG. 1 and the circuit block B of FIG. 5 at 20 ° C.

As is apparent from FIG. 3, by overhanging 3a of the two wiring patterns for the crystal unit of the circuit board 3 along the outer shape of the circuit board 3, the rate change caused by the humidity change is changed. It can be less than 1/2.

In this way, in this embodiment, the accuracy guarantee rate of the high-accuracy timepiece, such as 10 seconds per year, can be increased.

Here, as compared with the case where both the wiring patterns 3a and 3b are separated from the circuit board 3 and overhanged, the rate change amount can be similarly reduced, and as shown in FIG. Since the circuit board 3 is formed on the circuit board 3, the rigidity of the circuit board 3 between the IC chip 1 and the crystal resonator 2 can be increased, so that the change (fluctuation) in the mounting position of the crystal resonator can be reduced. it can.

Further, since the change in the mounting position of the crystal unit is reduced and the wiring pattern 3b is formed and fixed on the circuit board 3, the wiring pattern after the circuit board is mounted is fixed.
It is also possible to reduce variations in wiring capacitance between 3a and 3b.

Further, according to the present embodiment, the rigidity of the circuit board can be ensured and the rate change due to the humidity change can be reduced even if the two wiring patterns for the crystal oscillator are somewhat lengthened. The degree of freedom in the planar layout of the IC chip is significantly improved, and it becomes possible to manufacture a compact high-precision electronic timepiece.

FIG. 4 shows another embodiment of the present invention. In FIG. 4, elongated holes 3c are provided in the circuit board 3 to overhang the wiring pattern 3a, but in this case also, the same effect as that of the embodiment of FIG. 1 can be obtained.

In this case, since only the long hole 3c is formed in the circuit board 3, the rigidity of the circuit board 3 between the IC chip 1 and the crystal unit 2 is further increased as compared with the embodiment shown in FIG. be able to.

[Effects of the Invention] As described above, in the electronic timepiece circuit board of the present invention, one of the two wiring patterns for the crystal unit is formed on the board, and the other is separated from the board and overhung. As a result, the stray capacitance between the two wiring patterns can be reduced, and as a result, the rate change amount due to the change in the stray capacitance value due to the humidity change can be reduced.

Further, by wiring one of them on the substrate, the rigidity of the circuit board between the crystal unit and the wiring connection destination can be increased, and the displacement of the mounting position of the crystal unit can be reduced.

Moreover, since the positional displacement of the crystal unit is reduced and one wiring pattern is formed and fixed on the circuit board, it is possible to reduce the distance change between the wiring patterns when the circuit board is mounted. It is also possible to reduce variations in wiring capacitance due to changes in the distance.

Further, according to the present invention, the rigidity of the circuit board can be secured and the rate change due to the humidity change can be reduced even if the two wiring patterns for the crystal unit are slightly lengthened. The degree of freedom in the plane layout of the wiring pattern and the like is remarkably improved, and a compact high-precision electronic timepiece can be manufactured.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a circuit block for an electronic timepiece according to the present invention. FIG. 2 is a sectional view of FIG. FIG. 3 is a graph showing rate humidity characteristics of the circuit block A of FIG. 1 and the circuit block B of FIG. FIG. 4 is a plan view showing another embodiment of the electronic watch circuit block of the present invention. FIG. 5 is a plan view showing an embodiment of a conventional electronic timepiece circuit block. 1 ... IC chip 2 ... Crystal resonator 3 ... Flexible circuit board 3a, 3b ... Circuit resonator wiring pattern 3c ... Hole provided in circuit board 3 ... Molding agent

Claims (2)

[Scope of utility model registration request] 1. A circuit board for an electronic timepiece, wherein one of two wiring patterns conductively connected to a crystal unit is formed on a substrate and the other is separated from the substrate and overhanged. 2. An electronic timepiece comprising the electronic timepiece circuit board according to claim 1 of the utility model registration.