Yesterday i post a question i found it was not well described. After long research i found the term "Polymorphic Associations".
I try to find as simple solution as possible: MySQL - Conditional Foreign Key Constraints
But in my case the serial number is very important.The guide says in the link : product_id(in my case) will handle this. The problem is the product number is not exactly identify which ProductA or which ProductB was.
There is still problem that the implementation will be used in Cakephp which does not support composite primary keys.. Any advice?