High density interconnect verification of unpopulated multichip modules

Six methods of interconnect verification are discussed. Three are methods in general use for printed circuit applications and are becoming available for the higher resolution requirements of MCM (multichip module) substrates. Flying probe resistance testing is a direct, reliable test method but throughputs are too low for complex MCM substrates. Bed-of-nails (BON) resistance testers can be used for high-speed testing at the expense of high fixturing costs. Flying probe capacitance testers provide high throughputs but are less reliable than resistance testers. Flying probe combined resistance-capacitance testers have high throughputs with more reliable results. Two emerging technologies have been demonstrated to have some advantages over existing methods. Glow discharge testing is more reliable than capacitive testing and has much higher throughput. Voltage contrast electron beam (VCEB) testing has very high resolution and has ten times the throughput of any other electrical test method. VCEB is noncontact and nondamaging, allowing it to be used for in-process testing