电容传感芯片外部坏点的成因与控制

Cause and Control of External Dead Pixel of Capacitive Sensor Chip

外部坏点造成的不良是电容传感芯片制造过程中良率损失的主要来源之一。由于庞大的市场需求和日趋激烈的竞争,有必要进一步提升产品良率。从电容传感的原理出发,阐释外部坏点与产品实际物理结构之间的联系;按照失效分析的思路介绍了大粒径塑封填料颗粒异常混入、小粒径填料颗粒异常聚集和塑封料基体树脂异常聚集3类造成电容传感芯片外部坏点的典型成因;并借助有效介质理论归纳了相应的物理模型,给出大颗粒或聚集体临界尺寸的计算方法。在此基础上,依据外部坏点的物理表现和临界尺寸的计算结果,从塑封原材料的生产和塑封料的来料检验角度,分别提出了管控方案。根据实施方案前后同型号产品多批次因外部坏点导致的不良品扣料监控数据分析,几类措施均能有针对性地提升产品良率。

The defect caused by external dead pixel is one of the the main sources of yield loss in the manufacturing process of capacitive sensor chips.Due to the large market demand and the increasing fierce competition,it is quite necessary to further improve product yield.From the principle of capacitive sensing,the relationship between external dead pixel and the actual physical structure of the product is explained;According to the idea of failure analysis,three typical causes of external dead pixel of capacitive sensor chips are introduced,including abnormal mixing of large particle size plastic packing particles,abnormal aggregation of small particle size packing particles and abnormal aggregation of matrix resin of plastic packing materials.Based on the theory of effective medium,the corresponding physical model is summarized,and the calculation method of the critical size of large particles or aggregates is given.Based on the analysis,according to the physical performance of external dead pixel and the calculation results of critical size,from the perspective of the production of plastic sealing raw materials and the inspection of incoming plastic sealing materials,the control schemes are proposed respectively.According to the analysis of the monitoring data of defective product deduction caused by external dead pixel in multiple batches of products of the same model before and after the implementation plan,several kinds of measures can improve the product yield.