高分子材料組成與失效模型於電子連接器產業之應用

Abstract

高分子材料之機械強度雖不及金屬材料，然具有生產成本低廉與易於加工之特性，故廣泛應用於電子元件內部之連接器相關產品。為確保連接器元件內嵌之金屬端子零件結構穩固，業界常採用一保持力實驗，透過檢視金屬端子由高分子基座內部拔出之歷程，承受最大反作用力量作為判斷產品是否合格之評估依據。此外業界於數值模擬此類案例時，常採用簡單彈塑性質描述高分子材料機械行為，然此些模擬結果通常與實際量測數據之間具備明顯差異。 本研究檢視兩種類半結晶性(semi-crystalline)高分子材料，尼龍4T (polyamide 4T, PA4T)與液晶高分子(liquid crystal polymer, LCP)承受於相異應變率條件下之單軸壓縮負載反應，搭配適用於描述半結晶性高分子材料之組成律，自行撰寫為使用者副程式，掛載於有限元素分析軟體進行數值分析。該組成律基於過應力之黏塑性理論，可合理描述高分子材料對負載率與環境溫度之依賴性等機械行為。由於組成模型內材料參數繁多，故整合一自動運行之最佳化流程，藉此測試並擬合適當之材料參數組合。本研究亦探討數種前人研究中所提出，應用於描述高分子材料失效之準則適用性，經比對實務連接器產品之保持力實驗與模擬結果，揀選較適用於分析此類案例之失效準則。採用本研究提出之手法進行分析，無論於整體力量-位移曲線抑或保持力數值上，皆可獲致較採用業界常見手法準確之預測。

Polymeric materials are widely used in the industries such as aerospace, automotive and electronics due to relatively economical manufacturing cost and acceptable mechanical properties. Retention force of electronic connectors, in general one of essential specification requirements, is defined as a maximum force of metallic terminals withdrawn out of the corresponding plastic housing. It is not an easy task to numerically investigate the retention force based on the authors’ knowledge. Industry commonly applies the conventional elastic-plastic material model to assess the retention force, however the simulation analysis usually significantly underestimate the force based on the experiments. A finite element analysis is performed in conjunction with a self-coded user subroutine, accounting for relaxation/creep behaviors of semi-crystalline thermoplastic polymers under various loading conditions, to appraise the mechanical performance of two semi-crystalline thermoplastic polymers, saying polyamide 4T (PA4T) and liquid crystal polymer (LCP). Material parameters adopted in the constitutive model are evaluated by utilizing the optimization commercial software. Applications of the developed subroutine with several failure criteria to assess retention forces of two types of the connector are conducted. Calculation results agree fairly with the associated experimental measurements.