Answer:  PPM (Part Per Million) this field is where you would enter in the defect opportunities.

In the ROUTING screen, the PPM is opportunities for defects.  What this means is there are a certain number of things that can go wrong and cause a failure of the assembly.  The PPM is the total number of defects that might occur at each work center in the assembly of the product. 

Example:  If you have a board with one part on it, you can start with PPM = 2: the board can be wrong, and the part can be wrong.  But then you can expand on that by counting the number of leads on the component.  It is possible that if there are eight leads on the component, any one of them may have a bad solder joint.  So now the PPM is 2 + 8 or 10.  Now it is possible to insert the component backwards, so polarity is another PPM.  So now the PPM is 10 + 1 or 11.  It may be that the part is correct, the leads are ok, but it is defect.  Now the PPM is 11 + 1 = 12.  The 8 leads on the component must go somewhere, so there will be traces or conductors on the board.  Each of these may be a defective due to the manufacturing process by creating either shorts or opens.  So now the PPM is 12 + 8 or 20.

Lets say that there are two such parts on the board.  Now the PPM rises by the same complexity (but not the board itself), so now the PPM is 20 + 19 or 39 PPM.

There may be similar PPM's for each step in the process, depending on what is done in the process, and which parts might be affected.

So, if the work order is for a total of 100 boards (and we didn't add any other PPM's), then the PPM for the lot would be 3900.

What PPM is readlly intended to convey, is a measure of the quality of the boards assembled.  It is the number of defects observed in the lot divided by the total opportunities for defects.  In this example, if one board was found with one unsoldered pin, that would account for one defect out of 3900 possible defects, or approximately 256 PPM (1/3900*1,000,000).

Obviously, most assemblies will have much more PPM's than this example.  The Customers of Manufacturers sometimes require certain PPM quality or penailize the CM.  Of course, the Manufacturer will then attempt to make the PPM's as high as they can, to lower the defects.