EPCS128N issue unexpected erased

[Altera_Forum]

We have manufactured more than 70 units of a board that uses a CIV and a EPCS128M memory during the last 5 years. The boards are working without any problem. In the last fabrication of 25 units, some months ago, we have use a EPCS with the reference "EPCS128N 991W1 V5 MYS 013". We have found a problem in a significant number of these boards. After some weeks working, when we turn on the board we detect the FPGA is not configured, and memory is erased (when we read the memory all the positions has a value "FFh"). To get more information about the problem, We use a SW that turn ON / OFF the board each 30 sec and tests if the FPGA is configured. With previous fabrications we don't have any problem, but with the last fabrication we have detected this problem in a significant number of units. After we change the EPCS memory with another reference the boards have been working properly for weeks (with the turn ON/OFF Test). Have anybody used this EPCS reference or have found this kind of problem?

[Altera_Forum]

It looks like a bad batch. You should contact your supplier. 

Just to be sure, after you got a board to work again, did you try and solder back one of the supposedly defective EPCS chips and did you reproduce the problem? Just to be sure it wasn't a soldering problem that you just solved by a manual soldering operation.

[Altera_Forum]

I think that it is not a solder problem. Before to change the EPCS memory we check it. We have detected the problem in more than 9 units, in almost all boards it was posible to access to the memory, but in two of them it was not posible neither write neither read. 

Until now we have not soldered the memory in another board, but we are going to do it in a different board type.

[Altera_Forum]

Most probaly those are likely bad or defect devices since you have replace with new units EPCS128 and the configuration works. You may want to check with the devoce supplier and try to requalst for failure analysis.