Quality Control – Assurance JD.Berst, JM.Brom, april 2004 Quality Control – Assurance for the Front-End Hybrids (update april 2004)

10 % 3 % 6 % 20 % 1 % 36 % 5 % 12 % BATCH YIELD Prod BAD APV CHIP CIRC. VIA SHRT V250/ V125 G V125/ ASLY MANIP OTHER 040116_TIB6SU 93,68 285 18   1 6 4 2 040120_TOB6PU 85,60 250 36 5 040123_TIB6PD 96,42 279 10 3 040129_TOB4PU 90,00 200 20 040129_TEC4U 92,61 176 13 040129_TEC6U 94,23 104 040130_TEC6D 93,53 201 040218_TEC6U 92,78 97 7 040226_TOBP6U 85,91 291 41 21 040304_TEC4U 96,50 428 15 040309_TOB4PD 89,33 150 16 9 040312_TOB4PU 94,00 300 040323_TEC6U 83,75 80 040323_TEC6D 95,18 83 040325_TIB4PD 94,50 11 040326_TEC4U 97,39 153 040401_TIB4PD 92,88 267 19 12 040401_TEC4U 97,04 169 040407_TOB6PU 93,65 252 040413_TIB6PD 65,75 254 87 82 10 % 3 % 6 % 20 % 1 % 36 % 5 % 12 %

4 batches out of 21 with a yield less than 90 %

Bonding : an old problem…

The recently found hybrid open circuit problem : the VIA problem On batch 040120_TOB6PU : suspicions : an unusual number of hybrids have the same default : Open on the V250 (or V125) line. In the following batches : no problem (at a level less than 1%) On batch 040226_TOB6PU : confirmation of the problem … Investigations showed a prime suspect : The via(s) running from the bottom plane to the top and back. 2 faulty samples send to Cicorel for cutting and investigations. Last week : 5 FNAL modules showed a strange behaviour attributed to the same problem. FAULT : no V125 on the APV … No reference … Pedestals values subjects to external conditions (temperature, stress, light…)

These points should be linked together (and are not) 30216711602834 30216711602876 V250

The via is incompletely metallised Not reports of such fault on TIB hybrids Problem seems to affect only TOB hybrids CICOREL used for the TOB hybrids circuits which have been prepared on the same batch (1400 circuits) and stored before lamination A test cut on one of these circuits showed that the copper deposition was at the limit 10-11 microns instead of 12 -13 microns What may append : The via is incompletely metallised the conductivity is bad …. FHIT error …. FAULT the conductivity is OK …. FHIT OK ….. GOOD Under stress (thermal dilatation) the PBC expands a little and break the copper line inside the via …… ERROR By pressing on the via, it can be possible to restire the contact.

CONCLUSION : This has not been seen on earlier TOB batches ? - 041217_TOB is probably affected, but the bonding problem was discovered on this batch. No further investigation has been made… (under way) A long time before suspicion and confirmation (and action) ? - This problem may affect only one batch, at an visible extend of less than 10 % - Need a complete data taking to show the problem (FHIT is too fast) THIS MAY APPEND AGAIN : An impossible problem (evolution of a via…) can escape all the tests we made All failures have to be reported immediately (but with a production of 500 hybrids per week…) A re-analysis of all batches may always to be done (and it is posisble).

THE SHORT PROBLEM On the last TIB batch (040413_TIB6PD) poor yield (65%) 95 % of the failures of the same type : short circuit between V250 and V125 Re-analysis : problem present all the time Connectivity test … OK SMD mounting …. OK Connectivity test …. BAD (short) This problem can not (in principle) escape the tests. Possible explanation : Flow of soldering running trhu vias and making short on the bottom plane (?) Delamination (cold delamination) : some examples. BUT IMPOSSIBLE …. This is related to incomplete metallisation on some vias ?

New problems will probably arrive … Time insufficent for proper understanding Murphy’s law is still at work Reports on failures are very importants (mail to Alan , JMB, Web site ?) Reparations nearly impossible All QA parameters and results now in the DBase (query made by P. Juillot) 16000 hybrids needed : already about 4000 "wasted “ (200 k€)