SIR Testing

Operational Method

Samples are placed in an environmental chamber where the temperature and relative humidity are precisely controlled, often at eighty-five degrees and eighty-five percent. This sir testing continues for several days or even weeks, with measurements taken at regular intervals to track the performance of the insulation over time. The voltage applied during the test is similar to what the board will experience during its actual operation.

Any significant decrease in resistance is a sign of a potential failure in the field, even if the board passes all other functional tests. Because the test is time consuming and requires specialized equipment, it is usually performed during the design and qualification phase rather than during daily mass production. The data gathered provides a deep understanding of how the chemistry of the manufacturing process interacts with the materials of the board.

Regulatory Compliance

Authorities in the Chinese electronics industry, such as the Ministry of Industry and Information Technology, emphasize the importance of reliability testing for critical infrastructure. Products used in the 5G network, high speed rail and aerospace sectors must pass sir testing to prove they can survive the varied climates found across the country. Foreign companies operating in China often use these tests to validate the quality of local materials and to ensure that their global standards are being met.

The test results form a core part of the technical file required for product certification and for the approval of new manufacturing partners. If a material change is made, such as switching to a different supplier for solder paste, the test must be repeated to ensure no new risks have been introduced. Detailed reports from the environmental chamber are often scrutinized during quality audits by major international clients.

Process Validation

Information from the test allows engineers to optimize the cleaning process and the selection of conformal coatings. If the resistance drops too low, the team must investigate the root cause, which could be anything from poor rinsing of the boards to an incompatible combination of flux and solder mask. The sir testing method is particularly useful for evaluating “no clean” processes where the flux is intended to remain on the board after soldering.

It ensures that the residues are truly benign and will not become conductive when the product is exposed to moisture. In the competitive landscape of the Chinese electronics supply chain, the ability to provide successful reliability data is a major advantage for a manufacturer. Constant monitoring of insulation properties is the best way to prevent the late discovery of catastrophic design flaws.

Systematic testing under stress ensures the long term electrical integrity of the product.