Inventory control for waffer/die in substrate fabrication

[Former Member]

Hello gurus,

Looking for advice for inventory control of substrate fabrication. Fundamentally, how do we configure SAP such that 1 piece of a component (wafer) may yield different QTY's of sub-assemblies (sliced die), and plan MRP at the wafer level?

We use a wafer, say W-1, that may be printed into different size die based on the pattern being dispensed. This affects the yield of the wafer- EX, we can yield 121 of D-1 and 242 of D-2 using 1 piece of W-1 based on the print of the die. My question is, how do we configure SAP to plan to order the correct QTY of W-1 with these requirements? We are not able to use a fractional QTY of the die BOM for the wafer (i.e. a die BOM to consume 1/121 wafer per W-1 die). We have heard of solutions using UoM conversion (where 1 die EA = 1 die Sq Inches, so 121 Sq. Inches = 1 Ea Wafer). I have also heard solutions for alternate BOMs based on lot sizing... could this apply here also?

(1) W-1 -> (121) D-1 -> (121) Assembly-1; Demand for 1,000 Assemlby 1

(1) W-1 -> (242) D-2 -> (242) Assembly-2; Demand for 6,000 Assembly 2

How to get SAP to plan to order ~34 W-1?

Using R/3 release 7.3

Regards,

[Former Member · Accepted solution]

Timothy,

If I understand your question correctly I think this is fairly straightforward scenario.  First establish the following BOMs

BOM 1

Assembly1                                    121 EA

                D-1                               121 EA

                                W-1                  1 EA

BOM 2

Assembly2                                    242 EA

                D-2                               242 EA

                                W-1                  1 EA

For Material “W-1” set the Rounding Value (in MRP1 view) to 1.000.

If you have demand for 1000 Assembly 1 and 6000 Assembly 2 then when you run MRP here’s what would happen:

1000 Assembly 1 requires 1000 D-1 which would require 8.264 (=1000/121) W-1, but with the Rounding Value for W-1 set at 1.000, that gets rounded up to 9.

Similarly, 6000 Assembly 2 requires 6000 D-2 which would require 25.793 (=6000/242) W-1, but with the Rounding Value for W-1 set at 1.000, that gets rounded up to 25.

Total requirements for W-1 = 9 + 25 = 34.

Hope that helps.

Dave

[Former Member · Accepted solution]

Hello,

Thanks for the reply. In your example above, are you suggesting setting the base QTY for Assymbly1 and D-1 to 121 in CS02 BOM, and leaving W-1 with QTY (1) in the D-1 BOM?

[Former Member · Accepted solution]

Yes, exactly.

[Former Member · Accepted solution]

Dave,

Thanks, will try & check back-

[Former Member · Accepted solution]

Timothy,

Any luck?

Dave

[Former Member · Accepted solution]

Dave,

This was fairly straight forward as you suggested. MRP plans the correct QTY's using the configuration described above. We are having GPD issues upon shop order release instead. I will post questions in a different thread as we understand them better.

Thank you for your answer.

[Former Member · Accepted solution]

Timothy,

Glad to hear it!

Thanks,

Dave