GB/T 9491-2021 in English

Standard Evolution and Industry Significance

GB/T9491-2021, as a new standard replacing the 2002 version, adapts to the industry trend of popularization of lead-free solder and miniaturization of electronics. The newly added requirements of electrochemical migration test and PCB ion residue detection directly respond to the stringent requirements of high-density integrated circuits on soldering reliability.

Core classification system

Analysis of key technical requirements

5.8 Solderability index

Expansion rate requirements are significantly improved: Lead-free solder is increased from 65% in the 2002 version to 70-80%, verified by the copper plate solder ring test method specified in 6.9.1. In actual applications, after a communication equipment manufacturer used ROM1 type flux, the QFN package soldering yield increased by 12%.

5.13 Electrochemical Migration (ECM)

New test items are added, requiring that after 168h aging:
1) Insulation resistance ≥ 10% of the initial value
2) Conductor spacing reduction ≤ 20%
Verified by the 0.318mm gap comb circuit shown in Figure 3 to prevent the risk of short circuit caused by ion migration in vehicle electronics.

Innovative detection methods

Implementation recommendations

1. Material switching: When transitioning from traditional rosin type (RO) to resin type (RE), it is necessary to simultaneously verify the acid value (6.8) and copper mirror corrosion (6.12) performance
2. Process adjustment: The viscosity of paste flux (P) should be tested according to 6.5 before use, and it is recommended to maintain 800-1200cps at 20℃
3. Quality control: It is recommended to add 5.15 PCB ion residue batch inspection, and use the megohmmeter method to ensure that the NaCl equivalent is <1.56μg/cm²