Hands-free technology addresses critical temperature measurements

03/01/2005

FREMONT, Calif.-Two recently introduced, hands-free process optimization tools for semiconductor fabrication measure real-time, in situ temperature in solder reflow applications. The Process Probe 1935 thermocouple-instrumented wafer and Process Probe Custom Reflow Probe, developed by SensArray Corp. (www.sensarray.com), are designed to address the need for contamination-free thermal measurement brought on by the introduction of no-lead solder.

Lead-free solder in the reflow process has introduced new process monitoring issues for wafer-level packaging, since the higher melting point and upper temperature limitations imposed by potential heat damage to packaging components have shrunk the process window considerably. To ensure that the oven stays within the new, narrower temperature range for no-lead solder, the oven manufacturer or device maker needs to regularly measure oven temperature and uniformity.

"Temperature is a critical parameter in ensuring output of viable package assemblies from the reflow process,” explains Phil Marcoux, SensArray assembly and test business unit manager. “Oven settings can be delicate, and if they fall outside the process window, valuable product can be lost."

The Process Probe 1935 provides temperature measurement accuracy of +/- 1.5°C or +/- 0.25 percent reading (whichever is greatest in the isothermal chamber environment), as well as repeatable measurements in reflow and polymer curing ovens from 0° to 350°C. With the probe’s capacity of up to 34 embedded thermocouple sensors, SensArray says users can check wafer center-to-edge thermal stresses during loading and ramping, and calibrate temperature set-points in ovens.

Process Probe Custom Reflow Probes, meanwhile, let assemblers embed up to 34 thermocouple sensors in lead frames, strips or printed circuit boards for characterizing temperature profiles in ovens from 0° to 400°C. The device measures edge-to-center temperature for adjusting heater zone set points, and permits measuring and adjusting for drift in temperature due to oxide build-up on the heaters and belt.

Both devices' temperature measurement capabilities are via SensArray's wireless technology. The PDA-based Thermal TRACK measurement system is designed for hands-free, real-time, visual representations of wafer temperature and uniformity measurements necessary to characterize, optimize and maintain equipment thermal performance. A laptop-based Thermal MAP metrology system provides graphic representations of ramp-up, steady state, and ramp-down temperature, as well as tools that enable run-to-run and within-run analysis. III