Report from Florence

Bonding of Modules L12p

Mirko Brianzi

20 April 2004

CERN, 20 Apr 2004 Mirko Brianzi 2

Bonding Setup in Florence

Dage 3000Delvotec 6400

There is a new Pull Tester in our system,now we are finally able to make good pull test.

CERN, 20 Apr 2004 Mirko Brianzi 3

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 2004 Mirko Brianzi 4

PA movingThe 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:

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Gold pad movingSimilar problem bonding Bias to Filter Pad because the bond position is outside the Jig.

support

silicon

end of jig

bonds

carrier

Lateral View:

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Dirt

Sometimes bonding pads on PA are dirty and this has caused some fail.

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PA gap

For example…

PA-Si gap can vary between 100µm and 220µm.

302 000 200 35 277

302 000 200 35 278

Very difficult to reproduce exactly the same loop height because the mechanical assembly of the module influence the bond loop.

100

220

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VacuumBecause the mechanical difference between each module, sometimes the vacuum flex the silicon during bonding…

…so the central bonds can result 50µm higher (or more).

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Readout bonds

Loop heights are as much as possible (within the specifications).

240340

Specifications:min. 200µm max. 350µm?

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Bias bonds

Bonds in this module are too high but they have been corrected to 250µm.

370

Specifications:min. 200µm max. 350µm?

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Filter bondsIt’s very difficult to stay inside the specifications. 420525

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

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Pull Test on PA

Results of Pull Test on test bonds on PA

for 8 modules:

Mean force = 9.6g

Standard deviations = 0.22 - 0.37g

Abs. minimum value = 8.4g

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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 )

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Pull test correction

Measured geometry of bonds used for pull test to define the correction factor.

Factors:16°=1.8118°=1.6220°=1.4625°=1.1827°=1.1030°=1.00

Angles can vary depending on theexact point where the wire is pulled:25°-27° for PA test bonds => factor = 116°-20° for readout bonds => factor = 1.4

These factors seems very high…

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Pinholes after bonding

Found after bonding2 pinholes not presentin 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?

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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.