Report from Florence Bonding of Modules L12p Mirko Brianzi 20 April 2004

CERN, 20 Apr 2004Mirko Brianzi2 Bonding Setup in Florence Dage 3000 Delvotec 6400 There is a new Pull Tester in our system, now we are finally able to make good pull test.

CERN, 20 Apr 2004Mirko Brianzi3 Status Since March bonded 22 new modules (6 chips). For this L12p modules the loop height is very important, so it took a lot of time to set all the loop parameters and solve some problem. Now a new program for Delvotec is ready and it automatically bonds all the front side of the module, making all the loop shapes more reproducible (as much as possible). The failure rate for these modules has been 3fail/module because they are the first ones and we had to fix some problem, actually the last ones hadn’t any fail.

CERN, 20 Apr 2004Mirko Brianzi4 PA moving The main reason of failure is the PA not glued at the edge and this make often fail someone of the last bonds. Insert of teflon Making some pull test on bad bonds we can say that anyway too weak bonds are well visible. Solution:

CERN, 20 Apr 2004Mirko Brianzi5 Gold pad moving Similar problem bonding Bias to Filter Pad because the bond position is outside the Jig. support silicon end of jig bonds carrier Lateral View:

CERN, 20 Apr 2004Mirko Brianzi6 Dirt Sometimes bonding pads on PA are dirty and this has caused some fail.

CERN, 20 Apr 2004Mirko Brianzi7 PA gap For example… PA-Si gap can vary between 100µm and 220µm Very difficult to reproduce exactly the same loop height because the mechanical assembly of the module influence the bond loop

CERN, 20 Apr 2004Mirko Brianzi8 Vacuum Because the mechanical difference between each module, sometimes the vacuum flex the silicon during bonding… …so the central bonds can result 50µm higher (or more).

CERN, 20 Apr 2004Mirko Brianzi9 Readout bonds Loop heights are as much as possible (within the specifications) Specifications: min. 200µm max. 350µm?

CERN, 20 Apr 2004Mirko Brianzi10 Bias bonds Bonds in this module are too high but they have been corrected to 250µm. 370 Specifications: min. 200µm max. 350µm?

CERN, 20 Apr 2004Mirko Brianzi11 Filter bonds It’s very difficult to stay inside the specifications Specifications: min. 500µm max. 600µm In case that some bond is too low, we could accept it if it’s above a “safe limit” (350µm?). 3kV/mm (dry air) 500V=>170µm

CERN, 20 Apr 2004Mirko Brianzi12 Pull Test on PA Results of Pull Test on test bonds on PA for 8 modules: Mean force = 9.6g Standard deviations = g Abs. minimum value = 8.4g

CERN, 20 Apr 2004Mirko Brianzi13 Pull Test on Readout bonds Results of Pull Test on Readout bonds for 5 modules Mean force = 11.1g Standard deviations = 0.69 – 0.99g Abs. minimum value = 9.0g ( Correction Factor = 1.4 )

CERN, 20 Apr 2004Mirko Brianzi14 Pull test correction Measured geometry of bonds used for pull test to define the correction factor. Factors: 16°= °= °= °= °= °=1.00 Angles can vary depending on the exact point where the wire is pulled: 25°-27° for PA test bonds => factor = 1 16°-20° for readout bonds => factor = 1.4 These factors seems very high…

CERN, 20 Apr 2004Mirko Brianzi15 Pinholes after bonding Found after bonding 2 pinholes not present in the Database. 1 of them is probably caused by a fail during bonding. The correspondent bond have been removed… …in this case do we have to update the Bonding Database?

CERN, 20 Apr 2004Mirko Brianzi16 Conclusion New bonding program for Delvotec include also the automatic pattern recognition and it is fast and efficient (using some “trick” to avoid failure on PA). No problems with Data Base, it has been updated to the last version. Good and uniform pull test results.