Meaning
Environmental stress test involving the exposure of electronic components to elevated temperatures for a prolonged duration without electrical bias to assess long term reliability. high temperature storage evaluates the stability of materials and interfaces when subjected to thermal energy that accelerates chemical and physical degradation processes. This test is used to identify weaknesses such as intermetallic compound growth, moisture outgassing, and the breakdown of organic coatings. The boundary of this test is the maximum storage temperature specified by the manufacturer, beyond which the materials might undergo irreversible changes that do not occur in normal use.
In China, this procedure is a standard part of the qualification process for semiconductors and printed circuit board assemblies. It provides a way to estimate the shelf life and the service life of products that will be used in hot environments.
Thermal Stress
Constant exposure to high temperatures provides the energy needed for atoms to move and for chemical bonds to break or form. Unlike thermal cycling, which focuses on the stress of expanding and contracting materials, this test focuses on the steady-state degradation caused by heat. Common temperatures for this test range from 85 to 150 degrees Celsius, depending on the application and the material limits.
In the manufacturing centers of southern China, where ambient temperatures can be high, this testing is critical for ensuring that products remain functional throughout their intended life. The duration of the test can vary from a few hundred to several thousand hours, depending on the acceleration factor needed to simulate years of service. During this time, components are periodically removed and inspected for changes in electrical performance or physical appearance.
Degradation Marker
Changes in the microstructural state of the component are the primary indicators of a failure during this environmental test. One common marker is the excessive growth of intermetallic layers at the solder joints, which can make the connections brittle and prone to cracking. Another indicator is the oxidation of exposed metallic surfaces or the degradation of the plastic packaging materials.
In multi-layer boards, high temperatures can cause the delamination of the layers or the failure of the plated through holes. These physical changes often result in an increase in electrical resistance or a decrease in the dielectric strength of the insulation. By monitoring these markers, engineers can identify the failure mechanisms that are most likely to occur over time.
This information is used to improve the design of the product and to select more robust materials for the intended application.
Qualification Threshold
National oversight provided by the State Administration for Market Regulation and the Ministry of Industry and Information Technology enforces national standards like GB/T 2423.2 for dry heat testing. These regulations define the specific conditions and the acceptance criteria for high temperature storage tests for different classes of electronic equipment. Manufacturers must pass these tests to receive the China Compulsory Certificate and other required quality marks for their products.
Compliance with these standards is a prerequisite for selling goods in the domestic market and for participating in government procurement programs. The test reports must be generated by accredited laboratories and kept as part of the technical documentation for the product life. In the event of a product failure in the field, these records provide the evidence that the manufacturer followed the required safety and reliability protocols.
Producers who fail to meet these qualification thresholds may be required to redesign their products or face administrative penalties and loss of market access.
