Reliability engineering is applied to qualify packages, products and also to monitor the stability of the manufacturing process. Reliability tests at Richtek can be divided into two categories. Reliability testing results are analyzed for further circuit or process improvement.
Package reliability tests are used to verify the protection capability of a specific package and the manufacturability of SMT. During different temperature/moisture test conditions, package materials show different thermal stress, humidity resistance and chemical performance. The characteristics signal potential risk for chip assembly.
HTST: High Temperature Storage Test
THT: Temperature Humidity Test
HAST: Highly Accelerated Temperature and Humidity Stress Test
TCT: Temperature Cycling Test
Autoclave: Accelerated Moisture Resistance
Richtek follows the JESD22 series of standards for package reliability testing. iST and our assembly suppliers follow the same criteria in the reliability test services they provide Richtek. These package reliability tests are processed for the qualification of new assembly sites, new package processes and package BOM (Bill of Material) changes.
Given that package reliability tests take months to complete, they cannot provide real-time monitoring of process execution but these tests are an index of assembly process stability. Package reliability measures for process monitoring are applied to each assembly site based on the risk evaluation.
Resistance to ESD, latch-up and lifetime are evaluated in all Richtek products.
Resistance to ESD is a circuit and device-dependent characteristic. To reduce ESD risk during process, transportation and application we utilize ZAPMASTER (Thermo KeyTek) in-house and following the JESD22, MIL-883 series to evaluate each product. Different zap models (HBM, MM and CDM) are applied to our products and results are analyzed and fed back to quality improvement. iST and MA-Tek follow the same criteria in the ESD test services they provide Richtek.
Following JESD78, we use ZAPMASTER in-house to evaluate the latch-up capability of every product. iST and MA-Tek provide the same latch-up test service to RichTek.
HTOL (High Temperature Operation Life Test)
HTOL is an important test to evaluate product lifetime and design bugs. It simulates product operation. Both temperature and voltage acceleration are applied to each product. It also test foundry process stability.
Reliability tests are key to product improvement. Richtek utilizes its wealth of experience to inform product development for minimum risk and cost.