GB1561523A - Oscillator assembly - Google Patents

Abstract

The quartz resonator comprises a vibrator (12) and a mounting (10). The electrodes (13) formed on the faces of the vibrator and on the mounting (11) are gold films. The vibrator (12) and the mounting (10) are pressed with the aid of a tool (15) whilst the electrodes (13, 11) are heated to a temperature of below their melting point. This heating causes a diffusion of the metals of the electrodes so as to establish the mechanical link and electrical connection of the electrodes between the vibrator and the mounting. <IMAGE>

Description

(54) OSCILLATOR ASSEMBLY (71) We, KABUSHIKI KAISHA DAINI SEIKOSHA, a Japanese body corporate of 6-31-1, Kameido, Koto-tu, Tokyo, Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention concerns an oscillator assembly and, although the invention is not so restricted, it is more particularly concerned with an oscillator assembly for use in a timepiece such, for example, as a wrist watch.

According to the present invention there is provided an oscillator assembly comprising a quartz crystal oscillator having a plurality of tines, and a support which are provided with respective electrodes each of which comprises a gold films, the gold films of respective electrodes on the oscillator and support having respective surfaces which have been welded to each other by heat and pressure, the material between the oscillator and support consisting exclusively of gold.

The oscillator is preferably secured to the support only by way of said electrodes.

The support may be made of ceramic material.

The or each said film may have been produced by vacuum evaporation or sputtering.

The said respective surfaces may be welded to each other by maintaining them at substantially 3000C while pressing them together for a period of at least substantially one second.

The oscillator and support may be disposed within a sealed enclosure.

The tines of the oscillator may each be provided with a respective electrode, and each electrode may if desired have portions which are mounted on different tines.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is a perspective view of one known oscillator assembly, Figure 2 is a perspective view of another known oscillator assembly, Figure 3 is a cross-sectional view of the oscillator assembly of Figure 2, Figure 4 is a cross-sectional view of a first embodiment of an oscillator assembly to the present invention, and Figure 5 is a cross-sectional view of a second mebodiment of an oscillator assembly according to the present invention.

In Figure 1 there is shown a known oscillator assembly which comprises a support 2 of insulating material having a raised portion 2a on an upper surface 2b of which are mounted two spaced apart electrodes la, Ib.

A quartz crystal oscillator 4 of the tuningfork shape has two tines 4a, 4b and a base portion 4c from which the tines 4a, 4b extend. The base portion 4e is mounted on the surface 2b of the support 2 and is secured thereto by means not shown. The oscillator 4 is provided with electrodes 3a, 3b the major portions of which are respectively mounted on the tines 4a, 4b, although each electrode 3a, 3b has a portion which is mounted on the other tine. The electrodes 3a, 3b are provided on the oscillator 4 by printed circuit photo-etching techniques, while the electrodes la, 1 b are similarly provided by printed circuit photo-etching techniques on the surface 2b.

The electrodes la, 1b are electrically connected to the electrodes 3a, 3b respectively by means of wires 5 which are bonded to the respective electrodes.

The construction shown in Figure 1 requires considerable space on the surface 2b for the mounting of the oscillator 4 and therefore prevents the oscillator assembly of Figure 1 being made very small. In particular this is so because the electrodes 3a, 3b do not overlap the electrodes 1a, lb and are disposed therebetween.

Moreover, the use of wires 5 to interconnect the electrodes la, 1 b with the electrodes 3a, 3b involves the use of very fine wires which are easily bent, so that it is difficult to assemble the oscillator assembly of Figure 1 in a watch.

In Figure 2 there is shown another known oscillator assembly in which the disadvantages mentioned above are overcome. The Figure 2 construction is generally similar to that of Figure 1, like reference numerals indicating like parts, but it will be noted that wires 5 are not provided, the electrodes 3a, 3b being mounted vertically above the electrodes la, lb and being both electrically and mechanically secured thereto by means of a layer 6 of solder or electrically conductive adhesive as shown in Figure 3. As will be seen by comparing Figures 1 and 2, the Figure 2 construction enables the size of the oscillator assembly to be reduced since it is no longer necessary to space the electrodes la, l b as far apart.

However, if the electrodes on the oscillator 4 and support 2 are inter-connected by soldering, a preliminary soldering is required on the support 2 and/or on the electrodes 3a, 3b of the oscillator 4. Each electrode, however, normally has a tiny surface of approximately 0.2mm square so that the gap between the electrodes is very small, i.e. approximately 0.1 mum, with the result that fused solder is liable to bridge this gap so giving rise to a short circuit.

If, on the other hand, the layer 6 is constituted by an adhesive, the situation is similar, while if the adhesive is an epoxy resin, the liability of the latter to shrink affects the accuracy of the positioning of the oscillator 4 on the support 2.

In Figure 4 there is therefore shown a first embodiment of an oscillator assembly according to the present invention.

In the Figure 4 construction, a support 10, which may be made of a ceramic or other insulating material, is provided with two spaced apart electrodes 11 (only one shown) corresponding in shape and positioning to the electrodes la, lb of Figure 2. The electrodes 11, however, in contrast to the electrodes la, lb, are formed of gold films which have been applied to the support 10 by means of vacuum evaporation or sputtering.

The gold film of the electrodes 11 is provided directly on the support 10. Each of these gold films is produced by vacuum evaporation or sputtering.

The oscillator assembly also includes a quartz crystal oscillator 12 whose construction may be the same as that of the oscillator 4 of Figure 1, and may thus have a plurality of tines each of which is provided with a respective electrode 13, each electrode 13 having portions which are mounted on different tines.

Each of the electrodes 13 is constituted by a gold film which is mounted directly on the oscillator 12.

The oscillator assembly of Figure 4 is assembled by disposing the electrodes 11, 13 face to face and in contact with each other and mounting the support 10 on a base 16. The gold films of the electrodes 11, 13 are then welded to each other by maintaining them at a temperature of substantially 3000C (572"F) while pressing their adjacent surfaces 1 la, 13a together by means of a pressing tool 15 for a period of at least substantially 1 second.The temperature of 300"C is less than the melting point of the electrodes 11, 13 and the main tenancy of the electrodes at substantially 300 C effects inter-diffusion of the gold films of the electrodes 11, 13 with the result that the latter are welded to each other by heat and pressure, such welding having the effect that the oscillator 12 is secured to the support 10 only by way of the electrodes 11, 13 which thus constitute both an electrical and a mechanical connection.

If the support 10 is made of ceramic material, it may, as shown exaggeratedly in Figure 5, have an imperfectly flat surface 1 0a on which the electrodes 11 are provided. If therefore the electrodes 11 are formed by metalisation, the electrodes 11 cannot be properly secured to the electrodes 13 since these electrodes will not contact each other over a sufficient area, and this will give rise to stress concentrations in parts of the oscillator, and will therefore make the latter subject to damage. In order to avoid this possibility, gold films or sheets 14 may be interposed between the respective surfaces 1 1a, 13a and may be welded thereto by the said heat pressure.

Although not shown in the drawings, the oscillator 12 and support 10 are disposed in a sealed enclosure such, for example, as a glass case.

Thus the present invention enables one to produce a very small quartz crystal oscillator having high reliability and good quality and yet which can be easily assembled at low cost. Gold films do not become liquid in the manner of a solder or an adhesive and so do not give rise to the risk of a short circuit between the electrodes. Moreover, since gold does not creep, it does not give rise to thermal stresses which can damage the oscillator and this is so even if the coefficients of thermal expansion of the support 10 and of the oscillator 12 are not the same. The production of an oscillator assembly according to the present invention is, moreover, highly efficient because the connections between the electrodes is swiftly established merely by the pressing operation and the process requires no curing.

Having regard to the provisions of Section 9 of the Patents Act 1949, we draw attention to our British Specification No. 1,444,504.

WHAT WE CLAIM IS: 1. An oscillator assembly comprising a quartz crystal oscillator having a plurality of tines and a support which are provided with respective electrodes each of which comprises a gold film, the gold films of respective electrodes on the oscillator and support having respective surfaces which have been welded to each other by heat and pressure, the material between the oscillator and support consisting exclusively of gold.

2. An oscillator assembly as claimed in claim 1 in which the oscillator is secured to the support only by way of said electrodes.

3. An oscillator assembly as claimed in claim 1 or 2 in which one or more gold films or sheets are interposed between said respective surfaces and are welded thereto by the said heat and pressure.

4. An oscillator assembly as claimed in any preceding claim in which the support is made of ceramic material.

5. An oscillator assembly as claimed in any preceding claim in which the or each said film has been produced by vacuum evaporation or sputtering.

6. An oscillator assembly as claimed in any preceding claim in which the said respective surfaces are welded to each other by maintaining them at substantially 300cm while pressing them together for a period of at least substantially one second.

7. An oscillator assembly as claimed in any preceding claim in which the oscillator and support are disposed within a sealed enclosure.

8. An oscillator assembly as claimed in any preceding claim in which the tines of the oscillator are each provided with a respective electrode.

9. An oscillator assembly as claimed in claim 8 in which each electrode has portions which are mounted on different tines.

10. An oscillator assembly substantially as hereinbefore described with reference to and as shown in Figure 4 or Figure 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. of the Patents Act 1949, we draw attention to our British Specification No. 1,444,504. WHAT WE CLAIM IS:

1. An oscillator assembly comprising a quartz crystal oscillator having a plurality of tines and a support which are provided with respective electrodes each of which comprises a gold film, the gold films of respective electrodes on the oscillator and support having respective surfaces which have been welded to each other by heat and pressure, the material between the oscillator and support consisting exclusively of gold.

2. An oscillator assembly as claimed in claim 1 in which the oscillator is secured to the support only by way of said electrodes.

3. An oscillator assembly as claimed in claim 1 or 2 in which one or more gold films or sheets are interposed between said respective surfaces and are welded thereto by the said heat and pressure.

4. An oscillator assembly as claimed in any preceding claim in which the support is made of ceramic material.

5. An oscillator assembly as claimed in any preceding claim in which the or each said film has been produced by vacuum evaporation or sputtering.

6. An oscillator assembly as claimed in any preceding claim in which the said respective surfaces are welded to each other by maintaining them at substantially 300cm while pressing them together for a period of at least substantially one second.

7. An oscillator assembly as claimed in any preceding claim in which the oscillator and support are disposed within a sealed enclosure.

8. An oscillator assembly as claimed in any preceding claim in which the tines of the oscillator are each provided with a respective electrode.

9. An oscillator assembly as claimed in claim 8 in which each electrode has portions which are mounted on different tines.

10. An oscillator assembly substantially as hereinbefore described with reference to and as shown in Figure 4 or Figure 5 of the accompanying drawings.