CONTINUITY TESTING OF SOLID STATE CIRCUITRY DURING TEMPERATURE CYCLING

• US 3,842,346 A
• Filed: 12/20/1972
• Issued: 10/15/1974
• Est. Priority Date: 12/20/1972
• Status: Expired due to Term

• Current Assignee: Charles R. Bobbitt
• Original Assignee: Charles R. Bobbitt
• Inventors: Bobbitt, Charles R.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Hille, Rolf
• Application Number:
  US05/316,796
• Time in Patent Office: 664 Days
• Field of Search: 324/72.5,73AT,73PC,73R,158F,158P,158T
• US Class Current: 324/522
• CPC Class Codes: G06F 11/24 Marginal checking or other specified testing methods not covered by G06F11/26, e.g. race tests

Abstract

An inspection system for solid state circuitry formed on chips wherein circuits on a plurality of chips are scanned repeatedly in the presence of two different potentials, such as positive and negative probing pulses, during controlled temperature variations of the chips over a given range, for detecting continuity of the circuits on the chips under temperature conditions within the given range.

Claims

1. A method of inspecting a plurality of electronic devices, each device containing a like number of circuits, each of said circuits being electrically connected between at least two conducting means, said conducting means being located on said devices and being arranged for electrically connecting said devices to external electrical circuit means, said method comprising the steps of:

a. mounting said devices on a support means, b. testing a first one of said circuits in each of said plurality of devices for electrical conduction continuity in said first circuit by sequentially applying two different electrical potentials between two conducting means to which said one circuit is connected, said electrical potentials being of such magnitudes that the application of one electrical potential causes current to flow in one direction through said circuit and the application of the other electrical potential causes current to flow in the opposite direction through said circuit, and detecting whether the electrical conduction continuity of said one circuit is broken or now broken during the application of said electrical potentials to said conducting means, c. providing an indication of a lack of electrical conduction continuity for each device in which the electrical conduction continuity between the conducting means connected to said first circuit is determined to be broken, d. testing a second one of said circuits in each of said plurality of devices for electrical conduction continuity in said second circuit between two conducting means to which it is connected in the manner provided in step (b), e. providing an indication of a lack of electrical conduction continuity for each device in which the electrical conduction continuity between the conducting means connected to said second circuit is determined to be broken, f. testing in turn each of the remaining circuits of said devices, providing indications of any lack of electrical conduction continuity for those devices in which the electrical conduction continuity between the conducting means is determined to be broken, g. subjecting said devices to a temperature cycle of approximately one to five minutes time duration and approximately 75* to 100* C. temperature range as steps (b) through (f) are performed, said temperature cycle being of sufficient time duration to permit each circuit of each said device to be tested at least once during said temperature cycle.

2. A method of inspecting a plurality of plastic encapsulated integrated circuit devices, wherein each device contains a like number of electronic circuits and each of said circuits is electrically connected between a different pair of leads of said device, said method comprising the steps of:

a. detachably mounting said devices on a support means, b. sequentially applying two different electrical potentials across the pair of leads associated with a first one of said circuits in a first one of said plurality of devices, said electrical potentials being of such magnitudes that the application of one electrical potential causes current to flow in one direction through said circuit and the application of the other electrical potential causes current to flow in the opposite direction through said ciRcuit, c. detecting any lack of electrical conduction continuity between said pair of leads through said first circuit of said first device during the application of said electrical potentials, d. activating indicators associated respectively with said first circuit and said first device in the event that a lack of electrical conduction continuity is detected, e. sequentially applying the same two electrical potentials across the pair of leads associated with a first one of said circuits in a second one of said plurality of devices, said first circuit in said first and second devices occupying the same relative position within said devices, f. detecting any lack of electrical conduction continuity between said pair of leads through said first circuit of said second device during the application of said electrical potentials, g. activating indicators associated respectively with said first circuit and said second device in the event that a lack of electrical conduction continuity is detected, h. sequentially applying the same two electrical potentials in turn across the pair of leads associated with said first circuit in each of the remaining devices, said first circuit occupying the same relative position in said remaining devices as in said first and second devices, detecting any lack of electrical conduction continuity between said pairs of leads through said remaining devices during the application of said electrical potentials, and activating indicators associated respectively with said first circuit and any of said remaining devices in the event that a lack of electrical conduction continuity is detected in any of said remaining devices, i. sequentially applying the same two electrical potentials across the pair of leads associated with a second one of said circuits in said first device, j. detecting any lack of electrical conduction continuity between said pair of leads through said second circuit of said first device during the application of said electrical potentials, k. activating indicators associated respectively with said second circuit and said first device in the event that a lack of electrical conduction continuity is detected,

3. The method according to claim 2, in which the pair of leads associated with each circuit of said devices is inspected a plurality of times during said temperature cycle.

4. Apparatus for inspecting a plurality of electronic devices, wherein each device contains a like number of circuits and each of said circuits is electrically connected between at least two conducting means, and wherein said conducting means on each of said devices are arranged for electrically connecting said device to external electrical circuit means, said apparatus comprising:

a. support means upon which said plurality of devices may be detachably mounted, b. selecting means to select for testing one of said circuits in each of said plurality of devices, c. testing means, responsive to a selection operation by said selecting means, for testing in each of said plurality of devices the electrical conduction continuity in said selected circuit between two conducting means to which it is connected by sequentially applying two different electrical potentials between said two conducting means, said electrical potentials being of such magnitudes that the application of one electrical potential causes current to flow in one direction through said circuit and the application of the other electrical potential causes current to flow in the opposite direction through said circuit, and detecting whether the electrical conduction continuity of said circuit is broken or not broken during the application of said electrical potentials to said conducting means, d. indicating means, responsive to said testing means, for providing an indication of a lack of electrical conduction continuity for each device in which the electrical conduction continuity between the conducting means connected to said circuit being tested is determined to be broken, e. sequencing means, connected to said selecting means and responsive to said testing means, for causing said selecting means to select additional ones of said circuits in each of said plurality of devices for testing by said testing means, said sequencing means being actuated to cause said selecting means to select an additional circuit in each of said devices in response to the conclusion of a testing operation on each of said devices by said testing means, said sequencing means being operative to cause said selecting means to continue to select said additional ones of said circuits until all of said circuits of said devices have been tested, f. means for subjecting said devices to a temperature cycle of approximately 1 to 5 minutes time duration and approximately 75* to 100* C. temperature range, said temperature cycle being of sufficient time duration to permit each circuit of each said device to be tested at least once during said temperature cycle.

5. Apparatus for inspecting a plurality of plastic encapsulated integrated circuit devices while thermally cycling said devices through a predetermined temperature range, wherein each device contains a like number of electronic circuits and each of said circuits is electrically connected between a different pair of leads of said device, said apparatus comprising:

a. support means upon which said plurality of devices may be detachably mounted, b. circuit selecting means to select for testing one of said circuits in each of said plurality of devices, said selected circuits being located in the same relative position on each of said devices, c. means for sequentially applying two different voltage potentials acRoss the pair of leads in each device associated with a circuit which has been selected for testing by said circuit selecting means, said electrical potentials being of such magnitudes that the application of one electrical potential causes current to flow in one direction through said circuit and the application of the other electrical potential causes current to flow in the opposite direction through said circuit, d. detecting means for detecting a lack of electrical conduction continuity during the application of said electrical potentials between any of the pairs of leads associated with a circuit which has been selected for testing by said circuit selecting means, and for providing an output signal for each device in which there is a lack of electrical conduction continuity, e. indicating means, comprising a first set of indicators associated with respective ones of said circuits and a second set of indicators associated with respective ones of said devices, f. indicator latching means, connected to each of said second set of indicators, for maintaining any of said second set of indicators in an actuated condition once it has been actuated, g. sequencing means, connected between said detecting means and said indicating means, for connecting an output signal of said detecting means, if present, to the indicator of said first set of indicators which corresponds to a circuit selected for testing by said circuit selecting means, thereby actuating said indicator, and for sequentially connecting in turn output signals of said detecting means, corresponding to devices in which there is a lack of electrical conduction continuity for the particular circuit selected for testing, to the indicators of said second set of indicators associated with the respective defective devices, thereby actuating said indicators, h. control means, responsive to said sequencing means, for causing said circuit selecting means to select for testing in turn each of said circuits in said plurality of devices, and i. means for subjecting said devices to a temperature cycle of approximately 1 to 5 minutes time duration and approximately 75* to 100* C. temperature range, said temperature cycle being of sufficient time duration to permit said control means to cause each circuit of each said device to be selected for testing at least once during said temperature cycle.

6. The apparatus recited in claim 5, in which said control means causes each circuit of each said device to be selected for testing a plurality of times during said temperature cycle.

7. The apparatus recited in claim 5, in which the temperature subjecting means comprises means for alternatively heating and cooling said devices.

8. The apparatus recited in claim 7, in which the means for alternatively heating and cooling said devices comprises a thermoelectric heat pump.