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IBM
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Abstract
Plated through holes (PTHs) shorted to power planes or signal lines of multilayer printed circuit (PC) structures, e.g., boards or module substrates, are detected by measuring the short resistance value while heat from an external source is applied to the individual shorted PTH or, alternatively, to a group of PTHs which includes at least one shorted PTH. A shorted PTH in the presence of the applied heat results in a changing value of the measured short resistance. Thus, in the case where the heat is applied sequentially to each of the PTHs connected to the shorted power plane or signal line, each shorted PTH is localized, i.e., is individually identifiable with respect to its position in the PC structure.
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Thermal Method for Localizing High Resistance Shorts
Plated through holes (PTHs) shorted to power planes or signal lines of
multilayer printed circuit (PC) structures, e.g., boards or module substrates, are
detected by measuring the short resistance value while heat from an external
source is applied to the individual shorted PTH or, alternatively, to a group of
PTHs which includes at least one shorted PTH. A shorted PTH in the presence
of the applied heat results in a changing value of the measured short resistance.
Thus, in the case where the heat is applied sequentially to each of the PTHs
connected to the shorted power plane or signal line, each shorted PTH is
localized, i.e., is individually identifiable with respect to its position in the PC
structure. Likewise, in the case where the heat is applied sequentially to each
group of n plural groups of PTHs connected to the shorted power plane, each
group which contains a shorted PTH(s) is localized, i.e., each such group is
individually identifiable with respect to the particular group's position in the PC
structure. To speed up the short-localizing process for identifying individual
shorted PTHs, heat can be first applied sequentially to groups of PTHs to localize
the groups containing the shorted PTHs, and then only those groups so localized
would have the heat applied in sequence to the individual PTHs of the particular
group to identify the shorted PTH(s) of that group. The heat source may be, for
example,...