Molding Process
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Assembly Deviation Caused by Anisotropy of LCP Thermal Expansion Coefficient
Problem Phenomenon
【Problem Phenomenon】After temperature cycling, LCP precision parts show obvious directionality in dimensional change, producing stress or gaps at the fitting with metal inserts
Cause Analysis
LCP molecular orientation makes the longitudinal CTE as low as 0-0.007×10⁻⁶/℃ while the transverse reaches 0.022-0.062×10⁻⁶/℃; when mismatched with metal, thermal cycling produces interfacial stress; both the MEMS textbook and Plastics Industry Observation have data
Solution
During design, verify fit tolerances according to the actually measured directional CTE; select low-CTE mineral-filled grades for insert molding; if necessary, adjust the gate so that the orientation direction coincides with the assembly stress direction
Key Takeaway
LCP's CTE anisotropy spans two orders of magnitude; insert design must use actually measured directional values; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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