One-sentence answer: After the TWS charging case is closed, the seal strip and dispensed adhesive surface bear the pressure. The charging pin holes, Type-C port and indicator light hole are common water ingress paths. Sweat and rain intrusion cause charging pin corrosion and battery short circuits. Using the CTS Sentinel C28WE (C28) leak detector to perform vacuum decay air tightness testing on the entire case is suitable for inline interception on high-volume production lines.
The upper cover and lower case open and close via a hinge, and sealing depends on the compression of the seal strip or dispensed adhesive after closing. Axial clearance at the hinge and cover warpage both cause localized lack of compression.
Charging pin through-holes, the Type-C port, indicator light and reset hole are concentrated on a small area of the case wall, resulting in dense plugging points and high requirements for fixture positioning accuracy.
The individual part is extremely small with high output, so testing must minimize the time occupied by a single test while ensuring stable judgment.
Sealing locations: the seam seal strip between the upper cover and lower case, the dispensed adhesive surface, charging pin through-holes, the Type-C port, indicator light and micro-holes, and the hinge bushing area.Consequences of leakage: after sweat and rain intrusion, the charging pins oxidize and contact resistance rises, causing abnormal charging; the battery inside the case swells from moisture or short-circuits; a circuit fault inside the case can also prevent the earbuds from charging, resulting in a high after-sales repair rate.
The charging pin through-holes, Type-C port, indicator light and reset hole, as well as the axial clearance at the hinge. The fixture should preferably be a custom-formed cavity that compresses in one action; plugging point by point noticeably lengthens the cycle time and increases the risk of missed plugging.
At small volumes, pressure changes are more sensitive to leakage. Vacuum decay establishes a pressure differential without internal pressurization, and with ambient drift correction it achieves a more stable curve while avoiding pushing open the closed-cover sealing structure.
Converge the differences into program parameters and the custom-formed fixture. The C28 can store 32 test programs, so changeover only requires switching programs; the fixture maintains a consistent positioning datum, avoiding the need to re-adjust parameters and affect the criteria at each changeover.
No, 100% inspection is recommended. The seam seal of the charging case is affected by the closed-cover state and clamping, and defects are random, so sampling inspection can hardly represent the whole batch; once a leak escapes, the cost is a whole-unit return because the earbuds cannot be charged. The C28 has a short single-test time, supports online switching of 32 programs, and digital I/O can directly link with the sorting/rejecting mechanism, so it is capable of 100% inspection.
The key to TWS charging case air tightness is custom-formed plugging, stable judgment at micro volumes, and fast changeover. The CTS C28WE, with vacuum decay, ambient drift correction and 32 programs, adapts to multi-case-type mixed production. Combined with a custom fixture, it intercepts the risk of moisture short circuits before shipment.
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