A METHOD FOR TESTING THE OPERATIONAL EFFICIENCY OF A COMPONENT OF AN ELECTRONIC CIRCUIT

Abstract: The present invention relates to a method for testing the operational efficiency of a component of an electronic circuit at low temperature, comprising the steps of chilling the component and/or its connections to the remainder of the circuit and measuring the operational functioning of the component and its connections in the circuit. The invention is characterised by the further step of applying carbon dioxide in a solid state to the component and/or the component connections, wherewith the carbon dioxide vaporises while chilling the component and/or said connections at the same time.

Description: A method for testing the operational efficiency of a component of an electronic circuit. Technical Field The present invention relates to a method for testing the operational efficiency of a component of an elec¬ tronic circuit at low temperature, comprising the steps of chilling the component and/or its connections to the remainder of the circuit and measuring the operational functioning of the component in the circuit or the operational functioning of the component together with the functioning of its electrical connections or solely measuring the operational functioning of the electrical connections. Malfunctions which are difficult to detect are not unusual in electronic circuits. This is particularly true in the case of malfunctions which are due to variations in ambient temperature. One example of faults which lead to such malfunctions is so-called cold welds, where the circuit will operate correctly under certain conditions and will malfunction under others. For instance, at room temperature two cold- welded ends may be in contact with one another such as to provide a sufficiently effective conductor path for the circuit to function. When such a weld is exposed to low temperatures, for instance in the region of -50 β C, contraction will occur and the aforesaid ends will become spaced apart to such an extent as to impair conduction of electric current therebetween. The break in the conductor path can be readily detected at this low temperature. In other instances, it is desirable to replace a cir¬ cuit component and to test the function of the component at low temperatures. In these and similar circumstances, it has been normal to spray the circuit or the component connection with liquid freon and then test the functioning of the component in operation. The freon vaporises while chilling the component and is taken up by the surrounding atmosphere. The negative effect which freon has on the atmospheric ozone layer has become more and more apparent in recent years. This has lead to regulations which are intended to result in a reduction in the use of freon. One object of the present invention is to find a sub¬ stitute for freon in the detection of temperature- dependent disturbances in the functioning of electronic circuits. Another object of the invention is to provide an inex¬ pensive substitute which will not have a harmful effect on the surroundings. These objects are achieved with a method for testing the operational efficiency of a component of an elec¬ tronic circuit at low temperature which comprises the steps of chilling the component and/or its connections to the remainder of the circuit and measuring the operational functioning of the component in the circuit or the operational functioning of the component together with the functioning of its connections or solely measuring the operational functioning of the connections, and which further comprises applying solid carbon dioxide to the component and/or to the circuit- connections thereof, the carbon dioxide vaporising while chilling the component and/or its circuit connections at the same time. Advantageous further embodiments of the invention are set forth in the claims depending from claim 1. Condensed carbon dioxide boils at about -78 * C. Conse¬ quently, when carbon dioxide is stored in a pressure vessel, there is obtained a liquid and a gas phase at normal room temperature. It is therefore necessary to tap from the vessel carbon dioxide in its liquid state and consequently the orifice of the tapping conduit must be located in that part of the vessel in which the carbon dioxide is present in its liquid state. This tapping of the liquid carbon-dioxide is controlled with the aid of a conventional manually-operated valve and the carbon dioxide is delivered to a nozzle of rela¬ tively small diameter in the order of 0.1 to 0.9 mm, preferably in the order of 0.1 to 0.4 mm. When the liquid carbon-dioxide leaves the nozzle, it converts to solid carbon-dioxide ice, which then vaporises. The nozzle will preferably consist of an electrically insulating material, and more preferably an anti-static material, so that unintentional contact of the nozzle with the circuit will not result in a short circuit. According to one preferred embodiment of the invention the nozzle has the form of a hose with the aforesaid internal diameter and the hose-material has an electri¬ cal conductivity of from 2 to 100 megaohm per meter. This enables static which forms when the carbon dioxide is sprayed to be led away.

Claims: CLAIMS 1. A method of testing the operational efficiency of a component of an electronic circuit at low tempera¬ ture, comprising the steps of chilling the component and/or its connections to the remainder of the circuit and measuring the operational function of the component in the circuit together with the functioning of its circuit connections, characterised by the further step of applying carbon dioxide in a solid state to the component and/or the component connections, wherewith the carbon dioxide vaporises while chilling the com¬ ponent and/or said connections at the same time. 2. A method according to claim 1, characterised by chilling the component and/or said circuit connections to -70 β C or temperatures therebelow. 3. A method according to claim 1 or 2, characterised by applying the carbon dioxide with the aid of a nozzle made of an electrically insulated material. 4. A method according to claim 1 or 2, characterised by applying the carbon dioxide with the aid of a nozzle made of an anti-static material. 5. A method according to claim 3 or 4, characterised by using a nozzle which has a diameter of 0.1 to 0.9 mm, preferably a diameter of 0.1 to 0.4 mm.

Inventors: NORLEN STEN, OEHRSTROEM PER, NORLEN, STEN, OEHRSTROEM, PER
Applicants: AGA AB
Application year: 1990
Main classification: G01R31
IPC codes: G01R31