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

2. 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 %

3. 4 batches out of 21 with a yield less than 90 %

4. Bonding : an old problem…

5. The recently found hybrid open circuit problem : the VIA problem
On batch _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 _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…)

6. These points should be linked together (and are not)
V250

7. 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 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.

8. CONCLUSION : This has not been seen on earlier TOB batches ?
_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).

9. 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 ?

10. 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€)