JPS61152112A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To make a device suitable to face-to-face loading with excellent moisture proof by sealing the joint of an surface acoustic wave element part comprising a hermetically sealed box-shape body and a plastic cap with an adhesive and folding each lead protruding to the exterior of the box-shape body to the cap head part. CONSTITUTION:An elastic surface wave chip 16 is fixed with an adhesive 17 on an insulating plastic substrate 12 equipped with the I/O lead 13 and a grounding lead 14. Each electrode pattern and the leads 13 and 14 on the chip are connected through a bonding wire 15 to form the elastic surface wave element part. A plastic cap 18 puts on the element part. The joint of the element part and the substrate 12 is sealed with the adhesive so as to provide a sufficient moisture proof, and the end of each lead is folded along the side of the cap. Thus the moisture proofing processing and bonding work can be freely applied to the joint from the outside, therefore sealing work can be easily carried out in preventing a minute space from remaining between a sealing adhesive 19 and each member.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a surface acoustic wave device K housed in a plastic package, which has good moisture resistance and is suitable for mounting.

[Background of the invention]

In the package of a surface acoustic wave device, the surface of the surface acoustic wave chip must be in free space due to the nature of the surface acoustic wave element. A surface acoustic wave chip is attached to a lead implanted in a glass stem surrounded by a metal annular body, and a metal cap is placed over this to airtightly seal the metal-to-metal joint between the metal annular body and the metal cap. What stopped is
Although it exhibits good properties in terms of protecting the internal space from moisture intrusion from the outside, it is expensive. Therefore, as in the case of semiconductor devices, it is desired to realize a device using an inexpensive plastic package. The notable difference between surface acoustic wave devices and semiconductor devices is that in surface acoustic wave devices, there must always be free space in contact with the chip surface, and surface acoustic wave vibrations can occur on the surface of the surface acoustic wave element. The formation of moisture-resistant protective coatings or the like that would interfere with the process should be avoided.

As a conventional example of a surface acoustic wave device housed in a plastic (resin) package, for example, Japanese Patent Application Laid-Open No. 57-1382
There is one disclosed in Publication No. 11. As shown in FIG. 2(a)K, a surface acoustic wave chip is first immersed in a solution of a sublimable substance such as naphthalene 7, and crystals of naphthalene 7 are formed around the chip in the form of a lump. Figure 2 (b
), a film of silicone rubber 8 is formed on the surface of the lump by immersing it in two-component thermosetting silicone rubber 8.

Next, the whole is heated to simultaneously harden the silicone rubber film 8 and sublimate the naphthalene crystals, thereby completely forming a space 9 between the silicone rubber film 8 and the chip as shown in FIG. 2(0). Furthermore, as shown in FIG. 2(a)K, a film of resin 10 is formed by immersing it in a liquid of resin 10 such as epoxy and superimposing it on the film of silicone rubber 8. This package formation method does not use a mold or the like, so it can be easily handled even if the size of the surface acoustic wave chip is changed. Although it has the characteristics that perturbation is not inhibited even if the surface acoustic wave chip contacts the inner surface of the package due to impact, etc., there is a problem that the manufacturing process is complicated and it is not suitable for mass production.

Although not shown in the figure, a surface acoustic wave chip is attached to a lead implanted in a plastic stem, a plastic cap is placed on the outside of the chip, and a PJ is glued between the periphery of the stem and the inner surface of the cap. Burying and sealing is also practiced. This is similar to the structure of a vacuum tube, but
In the case of vacuum tubes, both the stem and the pulp are made of glass, and the sealing is done by heating the bulb from the outer periphery to soften it and fuse the nearly melted glass together, but the sealing mechanism is completely different.

When filling the gap with the above-mentioned adhesive, there is a problem in that minute holes tend to remain, and moisture easily infiltrates from the outside through such holes.

[Name of invention]

The object of the present invention is to provide a surface acoustic wave surface acoustic wave having a stem and cap adhesive structure that is easy to manufacture, has high moisture resistance reliability, and has a plastic package that allows mounting of the package as required. Device f: To provide.

[Summary of the invention]

In order to achieve the above object, the present invention uses an insulating substrate K having input, output, and grounding leads attached to its surface whose ends protrude outside the periphery, and a surface acoustic wave chip attached to an adhesive. A surface acoustic wave element is formed by wire bonding each electrode base on the chip and each lead end on the insulating substrate, and an insulating box-shaped cap is placed around the insulating substrate of this element. The periphery of the opening is bonded to form a sealed box-like body leaving a free space above the surface acoustic wave chip, and the joint portion of the element part and the cap forming the sealed box-like body is sealed with an adhesive. In addition, each lead protruding to the outside of this sealed box-like body is bent along the side surface of the cap toward the head of the cap. In this case, the insulating substrate and the cap made of insulating material are actually made of insulating plastic. .

The advantage of this structure is that moisture-resistant treatment and adhesive work can be freely applied from the outside to the bonding points around the cap and the substrate (this point differs from the conventional stem and cap sealing parts), and as a result, Sufficient moisture resistance can be obtained by sealing the joints using an adhesive. Furthermore, by bending the ends of the leads along the outer surface of the head of the box-shaped cap, it is possible to easily obtain a package suitable for mounting with nine sides, which has been difficult to achieve in the past despite the request.

[Embodiments of the invention]

91 (a) shows an insulating plastic cap 18t according to the present invention, and FIG. The surface acoustic wave element section is shown in which the chip 16 is fixed with an adhesive 17 and each electrode pattern on the chip and leads 15.14 are connected to the bonding wire 15. In addition, there are 20 protrusions for positioning the cap.

Cover this surface acoustic wave element part K with the cap 18.

The joint between the cap and the substrate 12 of the surface acoustic wave element section is sealed with an adhesive so as to have sufficient moisture resistance.

Further, by bending the end of each lead along the side surface of the cap, a surface acoustic wave device housed in a plastic package as shown in FIGS. 4(o) and 4(d) K side sectional view is obtained. In these figures, an adhesive is used to moisture-proofly seal the joint between the cap 19 and the substrate 12, and other symbols are the same as those in FIG. 4(b). If you K like this,
As mentioned above, in order to be able to freely perform moisture-proofing treatment and bonding work on the joints from the outside, it is necessary to ensure that there are no small gaps remaining between the sealing adhesive 19 and each component, which can serve as a path for moisture to infiltrate. It becomes possible to easily perform the sealing work. The sealing structure using the adhesive 19 as shown in FIG. 4(0) can provide sufficient moisture resistance, but if the area where the adhesive 19 is applied is widened as shown in FIG. The probability that a gap for moisture will remain will decrease, and even if a long connected gap remains, the route will be very long, making it difficult for moisture to infiltrate. With the structure of the present invention, even if the adhesive 19 is widely and thickly applied as shown in FIG. 4(d), it will not interfere in any way when connecting the surface acoustic wave device to an external circuit. Attach the lead K to the side of the cap 1B as shown in Figure 4 (8) K! It is also possible to provide a groove that is large enough to fit through the hole.

In addition, as shown in Fig. 4Ct) and (g)K, the cap 1
The end of the lead bent along the side surface of the cap 1B can be further bent along the outer surface of the head of the cap 1B to form a terminal for mounting. In this case as well, K as shown in FIG. 4(f).

The terminal may protrude from the outer surface of the cap by a certain amount, or it may be buried in the surface of the cap as shown in (g), depending on the user's requirements.

〔Effect of the invention〕

As explained above, according to the present invention, a stem having sufficient moisture resistance and an elastic surface sandwiched in a plastic package having a cap joint structure! is obtained, Sarajyo, Yong J.
Second, surface mounting allows for a terminal structure suitable for mounting.

[Brief explanation of the drawing]

FIG. 4(a) is a diagram showing a cap according to the present invention. The same figure (b) is a figure showing a surface acoustic wave element part concerning the present invention,
Figures (c) and (d) show embodiments of the present invention having different joint sealing structures, and Figure (s) shows an embodiment in which a groove into which the lead fits is provided on the side surface of the cap. Figures (r) and (g) are diagrams showing an embodiment with a terminal structure suitable for surface mounting, and Figures 2 (a) to (d) are diagrams showing conventional plastic packages. FIG. 2 is an explanatory diagram of a surface acoustic wave device. 12... Board, 13.14... Lead,
15... Bonding wire, 16... Surface acoustic wave chip. 17...adhesive, 18...cap,
19... Adhesive for sealing joints, 20...
・Protrusion for positioning the cap. O /III flr5A (C') (1> (1) years old 2 Fig.

Claims (1)

[Claims] 1) A surface acoustic wave chip having input and output comb-shaped electrodes formed on the surface of a piezoelectric substrate is connected to input, output, and grounding leads whose ends protrude outside the periphery. is fixed with adhesive to an insulating substrate attached to the surface, and each electrode pattern on the chip and each lead end on the insulating substrate are wire bonded to form a surface acoustic wave element, and the insulation of this element is The periphery of the opening of an insulating box-shaped cap is bonded to the periphery of the substrate, leaving a free space above the surface acoustic wave chip to form a sealed box-shaped body. 1. A surface acoustic wave device characterized in that the joint portion is sealed with an adhesive, and each of the leads protruding to the outside of the sealed box-like body is bent along the side surface of the cap toward the head of the cap. 2) The surface acoustic wave device according to claim 4, wherein the end portion of the lead bent along the side surface of the cap is further bent along the outer surface of the cap head to form a terminal for surface mounting.