Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1998-03-04
2001-12-04
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S1540PB, C324S754090, C361S777000, C257S048000
Reexamination Certificate
active
06326797
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to an apparatus and method which is used to evaluate the effect of solder substances on a printed circuit board populated with electronic components. Specifically, a test circuit board assembly is disclosed which when subject to a solder process, is useful for measuring the effects of the soldering process on circuit testability.
The processes for manufacturing printed circuit boards having mounted components interconnected by circuit conductors influences the circuit board test ability following manufacture. When changes to printed circuit board manufacturing assembly processes occur, such as changing fluxes and solder pastes which may require water cleaning of the circuit board, to fluxes and solder pastes which are designed not to be cleaned from the circuit board, the ability to test the circuit board assembly by conventional product testing facilities changes. While the changes to the processes may in fact not effect the circuit operation, the ability to test the circuit board assembly may be impaired.
Testing of completed circuit board assemblies conventionally requires a set of probes which are applied to the circuit conductors on the circuit board. The probes are of different design, and some may for a given solder processes, provide a better connection to a circuit board concuctor than others. Processes which involve the use of so-called no-clean fluxes and solder pastes, which are not to be removed from the printed circuit board, may pose a problem for testing the final product. While the residue from the no-clean flux and solder paste is not detrimental to product performance, the probes from a tester may not adequately make contact with the circuit board conductor when covered by a residue.
Because of the wide availability of different types of clean and no-clean fluxes and solder pastes, it is desirable to provide a common test vehicle which can evaluate the impact on testability for the use of any of these fluxes and solder pastes, and processes for soldering circuit board assemblies with these fluxes and solder pastes.
The testability of a circuit board assembly depends on the particular types of components being soldered to the surface of a board. Thus, while one component type may show no effects on testability after the use of a new no-clean flux and solder paste, other components may in fact make testability very difficult and unreliable.
The present invention provides a way for evaluating these processes prior to committing to any significant production of circuit boards.
SUMMARY OF THE INVENTION
It is an object of this invention to provide evaluation of in-circuit testability of a printed circuit board assembly.
It is a specific object of this invention to provide for in-circuit test evaluation of assembled circuit boards made in a particular manufacturing process using different types of circuit testing probes.
These and other objects in accordance with the invention are provided by a test coupon which is subject to solder processes. The test coupon includes multiple conductor patterns, terminating on a connector pin as well as at least one via hole and a circuit pad. Circuit components are soldered to pads on the multiple circuit patterns by a solder process. The selected components, as well as the via and circuit pads, represent typical circuit board structures which are soldered in a manufacturing process.
The resulting test coupon is subject to completed printed circuit board assembly testing. The test coupon having the mounted components is placed in an in-circuit tester where connections are made to the vias and pads of the circuit card by probes of the in-circuit tester. Electrical measurements including continuity measurements and component value measurements are made through the probes to verify the circuit testability. An accurate assessment of the manufacturing environment may be made without jeopardizing production hardware in an unqualified manufacturing process.
The multiple quadrants of the test coupon provide the ability to simultaneously test different probe types to determine whether or not the manufacturing processes affect the ability of a given probe type to connect to a respective conductor, pad, pin or via, on a circuit board.
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Caggiano Ray J.
Furr Boyd H.
Hatley Jeff A.
Noreika Richard Joseph
Connolly Bove Lodge & Hutz
International Business Machines - Corporation
Metjahic Safet
Nguyen Jimmy
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