翻译一小段话，请捣糨糊的不要使用网上的翻译机！！

Product A is using 4 different bottom piece (base?) designs and 2 of them often cause the lower passing rate. The reason is that each of this 2 designs only has 2 soldering points on the PCB, thus it is difficult to fix (onto what?) during the test.

A产品的所有型号一共使用4种底盘。其中有2种底盘的型号是经常影响通过率的。
A product all models altogether use 4 kind of chassis. And some 2 kind of chassis's model is affects the capacity frequently.

因为此2个型号，PCB焊接点只有2个，所以在测试的时候不是很好固定。
Because of 2 models, the PCB weld point has 2 for this reason, therefore in test time is not very good fixed.

ps，下面说的不要翻译，A指一个系列产品，A里面只要分几个大类的型号，然后这些型号产品的底盘一共有4中，这段话比较别扭，希望高手解答，我在线等 ：
ps, below said do not translate, A refers to a serial products, inside A, so long as divides several broad headings the models, then these model product's chassis altogether has in 4, these words are quite irritable, hope the master to explain, I online and so on: