In my personal experience, the cold joint could be due to manufacturer defect or mechanical stress that over-stress the connector's joint over time.
在我个人的经验,冷联合可能是由于制造缺陷或机械应力,过度强调连接的联合随着时间的推移。
It is a kind of special card making material which aim at finished product ID card (entrance guard, sell rice…), student card such need to cold joint personalizeddesign.