Thermal Method for Localizing High Resistance Shorts

Publishing Venue

IBM

Related People

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.

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,...