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Overview

Transient Calibration (TCAL) is the calibration technique Microsanj thermoreflectance imaging systems use to convert raw CCD reflectance images into accurate temperature maps for small features. Instead of (or in addition to) heating an entire sample uniformly on a temperature-controlled chuck, TCAL uses the device under test's own self-heating together with a region of known temperature or known thermoreflectance coefficient to calibrate the rest of the image, pixel by pixel.

TCAL calibration matters because the thermoreflectance coefficient — the relationship between a small change in reflected light intensity and a change in surface temperature — varies by material, surface finish, and coating. A single, uncalibrated coefficient applied across an entire image will produce inaccurate temperatures wherever the surface differs from the calibration reference. TCAL lets you generate a coefficient (or calibration) map that accounts for this variation across the field of view, which is especially important when you need accurate temperatures on small, non-uniform features such as transistor gates, channels, bond pads, or plated interconnects.

TCAL calibration applies to Microsanj thermoreflectance imaging systems (for example, systems built around SanjVIEW 7 acquisition software) used with:

  • A temperature-controlled thermal chuck (for example, the TC-100) for stage-based hardware calibration
  • An external K-type thermocouple probe, where used, for reference-temperature measurement
  • Devices that can be electrically pulsed or biased to generate self-heating (the device under test, or DUT)
  • Microsanj's calibration and analysis software: SanjVIEW 7, the standalone TCAL software (TCAL.exe), and SanjANALYZER+

Two complementary calibration workflows are described in this guide:

  • Stage/chuck-based calibration with TCAL software — a chuck-heated hardware calibration is captured in SanjVIEW, a "Movie Mode" image series of the pulsed device is recorded, and the TCAL software combines the two to generate a coefficient map.
  • Transient (pulsed) calibration with SanjANALYZER+ — a short, high-speed electrical pulse is applied to the device, and the resulting thermal decay is processed directly in SanjANALYZER+ using a known-temperature reference region, without a separate chuck-heated calibration step.

Which workflow — and which reference method — is appropriate depends on your device, its packaging, and what reference surfaces or sensors are available to you. The Application-Specific Notes section below covers guidance for Qorvo devices, TEA TTV samples, and electroplated gold surfaces specifically.