JPH0650794Y2 - 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 bond the copper foil when the wiring pattern is formed on the circuit board. The adhesive and the molding agent to increase the fixing strength 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 is changed from 40% to 90% at a temperature of 20 ° C, it will be about 0.05 to 0.07 sec / day, and for high-precision watches with a 10-year difference, 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 Problems] In order to solve the above-mentioned problems, the rotating board for an electronic timepiece according to the present invention is provided between two wiring patterns for a crystal oscillator, and has a long hole or a long hole substantially along the pattern. A slit is provided.

[Operation] According to the above configuration of the present invention, since the dielectric of the stray capacitance formed between the two wiring patterns for the crystal unit becomes air, the stray capacitance value can be reduced, and as a result, The rate change rate due to the change in the stray capacitance value due to the change in humidity becomes small.

[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. Chip, 2
A tuning fork crystal unit that oscillates at 32768Hz 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 agent for adhering the copper foil or the molding agent 4 protruding from the IC chip mounting portion.

As shown in FIG. 1, the circuit board 3 of this embodiment is provided with a hole 3c parallel to both wiring patterns between two wiring patterns 3a and 3b for a crystal unit. 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 providing the hole 3c between the two wiring patterns 3a and 3b for the crystal unit of the circuit board 3, the rate change caused by the humidity change can be reduced to 1/2 or less. You can

FIG. 4 shows another embodiment of the circuit block for an electronic timepiece according to the present invention. In the embodiment shown in FIG. 4, 2 for the crystal unit is used.
The slit 3e is provided between the book wiring patterns 3a and 3b. In this case, since the space between the two wiring patterns 3a and 3b is increased, the humidity characteristic is further improved as compared with FIG.

[Effects of the Invention] As described above, the circuit board of the present invention has the elongated holes or slits substantially along the wiring pattern between the two wiring patterns for the crystal unit, so that both wiring patterns are provided. Since the stray capacitance value formed between them can be reduced, it is possible to reduce the rate change due to the change in stray capacitance value due to humidity change, and increase the accuracy guarantee rate of high precision watches such as 10 seconds per year. it can.

Further, according to the present invention, even if the two wiring patterns for the crystal unit are made slightly longer, the rate change due to the humidity change can be reduced, so that the planar layout of the crystal unit and the IC chip can be freely set. The degree is greatly improved, and a compact high-precision electronic timepiece becomes possible.

In the embodiment, the hole 3c or the slit 3e is formed in the wiring pattern 3a.
And 3b, but the holes 3c or slits 3e are
The effect similar to that of the embodiment can be obtained as long as it is substantially along the wiring pattern of 3a or 3b.

[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 oscillator 3 ... Flexible circuit board 3a, 3b ... Wiring pattern for crystal oscillator 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, characterized in that an elongated hole or a slit substantially along the pattern is provided between two wiring patterns for a crystal oscillator. 2. An electronic timepiece comprising the electronic timepiece circuit board according to claim 1.