GB2258375A

GB2258375A - A radiation indicator

Info

Publication number: GB2258375A
Application number: GB9116342A
Authority: GB
Inventors: Amir Rosenheimer
Original assignee: Motorola Israel Ltd
Current assignee: Motorola Solutions Israel Ltd
Priority date: 1991-07-29
Filing date: 1991-07-29
Publication date: 1993-02-03
Anticipated expiration: 2011-07-29
Also published as: GB2258375B; GB9116342D0; JPH05215601A

Abstract

This invention relates to radiation indicators (10) which indicate the exposure of an electrical component (12) to ultra-violet (u.v.) radiation (11). With reference to Figure 1, a radiation indicator (10), comprising means receptive to incident ultra-violet radiation of energy greater than a predetermined threshold energy (Ethres), is coupled to an electrical component (12) susceptible to malfunction from the effects of said radiation. The means receptive to said radiation visibly changes (14) in some way in response to the radiation and indicates a likelihood that the device will malfunction. <IMAGE>

Description

A Radiation Indicator.

Background to the Invention.

This invention relates, in general, to radiation indicators and, more particularly, to radiation indicators which indicate the exposure of an electrical component to ultra-violet (u.v.) radiation.

Summary of the Prior Art.

Many electrical components are subjected to working environments which effect their operational capacity. For example, exposure to either high energy ultra-violet radiation or the cumulative effects of prolonged exposure to low intensity u.v. radiation, such as incident sunlight or certain fluorescent lamps having wavelengths in the range of 3000-4000A, can cause destruction or electrical malfunctions of the components. This undesirable effect is especially prevalent in, for example, semiconductor devices, such as EPROMs employing floating gate technologies.

It can therefore be appreciated by one skilled in the art that it would be desirable to clearly identify an electrical component on the verge of an electrical malfunction which has resulted from the effects of irradiation.

Summarv of the Invention.

In accordance with a preferred embodiment of the invention, there is provided a radiation indicator coupled to an electrical component susceptible to malfunction from the effects of incident ultra-violet radiation of energy greater than a predetermined threshold energy. The radiation indicator comprises means receptive to said radiation, wherein said means visibly deforms from the effects of incident radiation of energy greater than the threshold energy. This has the advantage of clearly identifying the exposure of the component to ultra-violet radiation and, more specifically, indicating that an operational malfunction is likely to occur as a result of accumulated irradiation thereof.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings.

Brief Description of the Drawings.

Fig. 1 illustrates an electrical component (semiconductor package) which features a radiation indicator in accordance with a preferred embodiment of the present invention.

Fig. 2 graphically illustrates the deformation of a radiation indicator with respect to time in accordance with the preferred embodiment of Figure 1.

Fig. 3 illustrates an alternative embodiment of the present invention comprising a stack of radiation indicators coupled to an EPROM.

Detailed Description of the Preferred Embodiment.

Figure 1, illustrates a preferred embodiment of the present invention in which a radiation indicator 10 is coupled to an electrical component 12, such as a semiconductor.

The radiation indicator 10 is comprised from an ultra-violet absorbent material which deforms in the presence of incident ultra-violet radiation 11 of energy E greater than a minimum threshold energy Ethres. The material may be a hydrocarbon, such as the polypropylene "Plastor" (for further information refer to UK patent application GB 1586344), manufactured by Plastopil Hazorea, which disintegrates after prolonged u.v. exposure. Furthermore, such polymers may be impregnated with coloured dyes or pigments. These dyes and pigments are susceptible to colour change through exposure to incident u.v. radiation. It should be appreciated by one skilled in the art that any u.v. absorbent material which deforms in the presence of u.v. radiation could be used as an acceptable alternative. The u.v.

material is formed into a sheet which produces the radiation indicator 10. The radiation indicator 10 is coupled to an exposed surface 15 of the electrical component 12. Coupling is performed through the application of an adhesive 13 therebetween. It should be appreciated by one skilled in the art that alternative methods of adhesion, such as a deposition process of the u.v. material to form the sheet, are equally applicable. Exposure to u.v. radiation 11, of wavelengths shorter than 4000A, causes deformation 14 of the radiation indicator 10. This deformation 14 can take a number of forms: (i) disintegration (as in the case of polypropylene produced by Plastopil Hazorea); (b) a visible colour change within the material; or (c) a visible deformation in the surface e.g. rippling.Since the total deformation of the material is proportional to the incident radiant energy which has fallen on the material over a period of time, a radiation indicator 10 with a predetermined exposure limit can be manufactured. A radiation indicator 10 with a radiant energy absorbency of deformation less than that for the electrical component 12 is used. With reference to Figure 2, deformation of the radiation indicator 10 at time a indicates that the electrical component 12 is approaching probable component malfunction at time p. Ideally, total deformation of the radiation indicator 10 should occur a short time 8t before probable component malfunction occurs.

The two curve profiles in Figure 2, illustrate radiation indicators 10 comprised from materials with different physical properties. Curve 1 illustrates a u.v. absorbent material which deforms at a constant rate for a given intensity of incident u.v. radiation Io. Curve 2 illustrates a material which has a non-uniform rate of deformation for an identical intensity of incident radiation Io. A curve profile as illustrated by Curve 2 provides a radiation indicator 10 which has a rapid and more visible deformation. At time y, the rate of deformation of the radiation indicator 10 increases substantially.Curve profiles such as these may be obtained through the controlled variation of the properties of the u.v. absorbent material through its cross-section, the initial selection of the material or the appropriate mechanical arrangement of the material e.g. pre-stressing. Typically, dimensions for the radiation indicator 10 would be 10mm x 10mum x imam.

An alternative embodiment of the present invention (Figure 3) allows for the multiple exposure of a device, such as an EPROM 31. In such embodiment, a stack 30 of such radiation indicators 10 is produced by the successive coupling and stacking of a plurality of u.v.

absorbent materials together. Such a configuration indicates the erasure of data within the EPROM 31, allows for the numerous reprogramming thereof, and also indicates the end of the operational life-span of the EPROM 31.

It can therefore be appreciated that an invention so designed and described produces the novel advantages of a small, low cost radiation indicator which clearly indicates the exposure of an electrical component to significant levels of incident ultra-violet radiation.

It will, of course, be understood that the above description has been given by way of example only, and that modifications in detail may be made within the scope of the invention. For example, the hydrocarbon may also comprise a vinyl polymer, a nonionic organosoluble antioxidant complex of a transition metal and a nonionic transition metal complex acting as an ultra-violet light stabilising compound.

Claims

Claims.

1. A radiation indicator (10) comprising means receptive to incident ultra-violet radiation of energy greater than a predetermined threshold energy, wherein: the indicator (10) is coupled to an electrical component susceptible to malfunction from the effects of said radiation; and said means visibly deforms from incident radiation of energy greater than the threshold energy.

2. A radiation indicator (10) in accordance with claim 1, wherein the rate of said deformation is proportional to the intensity of said incident ultra-violet radiation at a given time.

3. A radiation indicator (10) in accordance with claim 2, wherein the electrical component comprises a semiconductor.

4. A radiation indicator (10) in accordance with claim 3, wherein the semiconductor is a programmable memory device.

5. A radiation indicator (10) in accordance with claim any preceding claim, wherein the means receptive to incident ultra-violet radiation is comprised from a hydrocarbon compound.

6 A radiation indicator (10) in accordance with claim 1, wherein hv the predetermined threshold energy (E = 2~) corresponds to a wavelength of 4000 Angstroms (4000A).

7. A radiation indicator (10) substantially described herein, with reference to the accompanying drawings.