Flying Probe Tester Solution for Advanced Package

We report that we have developed two solutions for testing Advanced Packages.
1. Flying Probe Tester with Active Thermal Control
Substrates used in AI servers and autonomous vehicles are exposed to high temperatures. These substrates are composed of various materials such as metal, resin, and glass, each with different coefficients of thermal expansion. As a result, they are prone to physical stress under high temperatures, which can potentially lead to cracks in vias and wiring. Traditionally, quality assurance under high temperatures has been conducted by measuring the wiring resistance before and after thermal stress testing. However, once cooled, the substrate returns to its original state, causing defects that were apparent at high temperatures to appear normal at room temperature, presenting a challenge.
To address this issue, we have developed a Flying Probe Tester (FPT) that performs resistance testing while heating the substrate. This FPT consists of three stages: heating, thermal retention inspection, and cooling. Initially, the substrate is mounted on a fixture and heated along with the fixture during the heating stage. Once the target temperature is reached, the fixture is transferred to the thermal retention inspection stage, where testing is conducted while maintaining the high-temperature state. After the inspection is completed, the substrate and fixture are moved to the cooling stage, where they are cooled back to room temperature. Through previous experiments, we have successfully identified abnormal values that were undetectable at room temperature.

2. High Precision Flying Probe Tester “contact phi 14um pad with Kelvin probe” With the expansion of the AI semiconductor market, chiplets are gaining attention. To enhance semiconductor chip performance and reduce power consumption, the micro-wiring of interposers and silicon bridges used in chiplets is becoming increasingly refined. The four-terminal resistance method using Kelvin probes is effective for inspecting wiring quality; however, contacting Kelvin probes with micro-bumps has been challenging.
To solve this issue, we have developed an FPT and probe capable of contacting phi 14um pads with Kelvin probes. This FPT consists of four arms: Front 2 arms and Bottom 2 arms, with a positional accuracy of ±2.8um for all arms and a pin-to-pin pitch of 2um for the Kelvin probes. Additionally, it features a contact check-down function to prevent crushing micro-bumps. When the Kelvin probes make contact with a micro-bump, current flows between the probe pins, allowing for detection of contact and stopping further probe descent. With a minimum resistance measurement capability of 400uohm, it is suitable for inspecting wiring quality. This FPT contributes to the long-term stable operation of high-performance semiconductor chips.