Key points of cold and hot shock testing for IGBT chips

In the field of power electronics, IGBT (Insulated Gate Bipolar Transistor) chips play a crucial role and are widely used in various power electronic devices. In order to ensure the reliability and stability of IGBT chips, strict testing is required in their design and manufacturing process, among which cold and hot shock testing is one of the crucial steps. The cold and hot shock test aims to simulate the extreme temperature changes that IGBT chips may encounter in practical applications, in order to evaluate their performance and reliability under various environmental conditions.

Chip testing almost always relies on temperature shock testing, and IGBT chips need to undergo countless reliability tests to ensure safe and efficient use. IGBT requires temperature shock testing machines to perform some environmental reliability tests. Common industrial grade IGBT reliability tests include but are not limited to the following items:

(1) HTRB (High Temperature Reverse Bias) Test: The HTRB test is used to verify the reliability of IGBT leakage indicators under stable conditions. The main focus of HTRB testing is on the edge structure and passivation layer of IGBT chips, as well as ion pollutants related to production. During the HTRB test process, the variation of leakage current over time can generally be monitored.

(2) HTGB (High Temperature Gate Reverse Bias) Test: The HTGB test is used to verify the stability of gate leakage current under electrical and thermal loads. The main focus of the HTGB test is to assess the integrity of the gate oxide layer of IGBT and mobile ion contamination. It is recommended to continuously monitor the leakage current and turn-on voltage of the gate during the experiment. If these two parameters exceed the specified specifications, it is considered that the module will not pass this test.

(3) H3TRB (High temperature and high humidity reverse bias) test: The H3TRB test is used to test the effect of humidity on the long-term characteristics of power devices. The focus of H3TRB testing is on the passivation layer of IGBT and surface defects of the chip, including weak links in the entire device structure. It is worth noting that measuring the leakage current immediately after the H3TRB test may result in leakage exceeding the standard. The reason for this is that most module designs are not completely sealed, and water vapor can also reach the passivation layer over time, leading to leakage exceeding the standard after the test. Therefore, the device can be baked for 2-24 hours and restored to room temperature for 24 hours before testing its leakage current to verify the possibility of water vapor intrusion.

(4) TST (Temperature Shock) Test: The TST test mainly verifies the resistance of IGBT to mechanical stress under passive temperature changes. The focus of TST test assessment is on the packaging of IGBT modules and the connection between the substrate and DCB.

(5) TC (Temperature Cycle) Test: TC test is used to simulate the impact of external temperature changes on IGBT, verify the overall structure and materials of devices or modules. Especially for IGBT power modules, a system is composed of different materials. When heated or cooled, the thermal expansion coefficients of different materials differ greatly, and the mechanical stress on the two interfaces during heating or cooling is greater. The focus of the TC experiment is on the connection between the IGBT chip and the DCB, as well as between the DCB and the substrate.

(6) PC (Power Cycle) Test: There are two types of power cycles: second level power cycle (PCsec) and minute level power cycle (PCmin). During the test, the chip is actively heated to the target temperature by its own working current, then the current is turned off and cooled to the specified temperature. The second level power cycle test mainly assesses the reliability of the near chip end connection; The minute level power cycle test mainly assesses the reliability of the connection between the near chip end and the far chip end.

By strictly implementing cold and hot shock testing and evaluating and improving the IGBT chip based on the test results, its reliability and stability can be effectively improved, ensuring its normal operation under various environmental conditions. In the field of power electronics, this is crucial for ensuring the safety and performance of equipment.