One-sentence answer: Automotive camera modules are small in size and contain optical elements and circuits inside. A micro-leak at the lens barrel adhesive joint or the housing seal ring will let moisture condense on the inner side of the lens, causing blurred imaging and black spots. Using the CTS Sentinel C28WE (C28) leak detector to test the module cavity by vacuum decay is a feasible air tightness test solution for module production lines.
The internal cavity of the module is very small. Any temperature fluctuation or deformation of the plugging cavity will dominate the pressure curve, requiring higher instrument stability than for large parts.
After a trace amount of moisture enters, condensation forms on the inner side of the lens, directly appearing as image fogging, black spots or nighttime glare. This is perceivable by the user and is a zero-tolerance defect.
The adhesive bonding of the lens barrel and housing, and the potting at the harness outlet, are affected by adhesive amount, curing and ambient humidity, making hidden partially unfilled channels likely.
Sealing locations: the O-ring or dispensing surface between the lens barrel and the rear housing, the adhesive bonding ring between the lens and the lens barrel, the potting area at the harness outlet, and the joint surface between the rear housing and the PCB seat.Consequences of leakage: after moisture intrusion, condensation forms on the inner side of the lens and imaging quality degrades; the circuit is affected by moisture, causing short circuits or abnormal image signals; surround view, reversing and other ADAS functions are degraded, which is a safety-related functional failure of the vehicle.
The module does not allow internal pressurization, and the lens adhesive joint and optical parts are sensitive to pressure; vacuum decay establishes the test pressure difference by drawing vacuum from the outside, while avoiding the introduction of oil contamination and particles onto optical surfaces, so it is the more suitable method.
Control the plugging cavity volume, avoid deformation of the fixture itself, and keep the ambient temperature stable. The ambient drift correction and absolute pressure sensor of the C28 can offset ambient fluctuations, but the plugging cavity design should still stay as close as possible to the product shape.
OEMs usually cite the IP grade requirements of IEC 60529 / GB/T 4208 and convert them into internal air tightness limits; the specific limits should be agreed in the technical agreement, and the instrument performs judgment according to the program.
Yes, the two have different roles. Water testing is a final inspection method, usually performed by sampling or destructively, and judgment relies on the human eye and later observation, so it cannot give a continuous value; air tightness testing is quantitative, non-destructive and can be 100% inspection, intercepting defects after assembly and before shipment while leaving traceable data. Air tightness testing handles upstream screening and water testing handles type confirmation, which is a common production line combination.
The focus of air tightness for automotive camera modules is stable judgment in small volumes and no contamination of optical surfaces. The CTS C28WE, with vacuum decay, ambient drift correction and 32 programs to adapt to multiple module models on one line, together with custom-formed plugging fixtures, forms a traceable defense line for module waterproof quality.
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