adhesive test program - ge.infn.it · adhesive test program, dec 6th 2001 3 3 glue joints on...

C. Gemme – University and INFN / Genova Pixel week, Cern, Dec 6th 2001

Adhesive Test ProgramClaudia Gemme / INFN - Genova

ü Adhesives needed to assembly a moduleü Status of each adhesiveü To do list

Adhesive Test ProgramAdhesive Test ProgramClaudia Claudia Gemme Gemme / INFN - / INFN - GenovaGenova

ü Adhesives needed to assembly a moduleü Status of each adhesiveü To do list

22Adhesive test program, Dec 6th 2001

Module parameters to be assessedModule parameters to be assessed

C-C

MS adhesive:3 candidates Modules:

· 2 bump types

Flex-sensor interface· Different candidates· Different gluing

patterns and methods

Potting:· Different candidates· different methods


Glue Joints on ModulesGlue Joints on ModulesAt least 5 adhesives are needed during module assembly:� Flex on test support frame;� MCC on Flex;� Pigtail to Flex;� Flex to module:

ü Under the MCC;ü Under the Pigtail;ü Under the FE’s wire bonds;

� Module to Carbon-Carbon support.� Wire bonds potting.

General comments:ü No stress on bumps during thermal cycles (or other fragile points as flex

traces, wire bonds....).ü Experience in some labs with thermal cycles with hot/dummy modules.


Flex on support frameFlex on support frameRequirements:� allow wire bonding flex/frame;� maintain properties up to ~200 0C (flex glued on frame before SMD

mounting).Experience:� Only Bonn has experience on this topic: suggested high temperature epoxy.� Some experience now in Oklahoma for flex V3: chip tacking adhesive.To do list:� Is the Flex flat enough for probing?� Needed some pins during gluing for a better alignment?� Experience needed with flex V3.


MCC on FlexMCC on Flex

Requirements:� radiation hard;� quantity small enough not to wet the wire bonds pads;� electrically conductive;� thermally conductive (?, how many mW?);� no mechanical requirements;� no requirement on curing temperature/time or pot life.Experience:� Mipot: Epotec H20 in the centre + Epotec H70 outside the ground pad;� Bonn: E-SOLDER 3025 Silver epoxy.


Pigtail to FlexPigtail to FlexRequirements:� radiation hard;� quantity small enough not to wet the wire bonds pads;� no requirements on electrical and thermal conductivity;� requirement on curing temperature: if the pigtail attached after the flex-

module assembly, Tcuring <60 0C;� mechanical requirements: through the pigtail possible stresses on the

module (at least it will be permanently bent, …). This effect has to bestudied combined with the glue used to attach the flex on the module (4b).Peel strength constraint?

Experience:� Bonn: Pyralux LF 0300 Epoxy Prepreg foil (high temperature required).To do list:� Quantify the strength on the module when the pigtail is bent.� Verify possible damage on bumps (AMS-Genova, IZM-Bonn).� Pigtail has to fixed by clamp to the module/stave support during module

test.


Flex to bare moduleFlex to bare moduleMain Requirements:� keep the flex attached to the sensor:

å quantity enough to handle the module when attaching it to the stave;� support the stresses coming from the pig tail;� quantity small enough to reduce coupling flex-module and minimize CTE

mismatch;� uniformity (glue/not glue) under flex wire bonding pads;� no glue on the sensor alignment marks;� electrically not conductive;� radiation hard;� curing temperature < Tcuring <60 0C; short curing time (if possible).

Minor Requirements:� No glue in the guard ring region (? sensor tests and experience seem to

show no difference);� thermally conductive under the MCC (?);� pot life > 1 hour (more modules with the same glue…);� applied on the flex or the sensor by a dispenser (automatic and

reproducible way).


Deposition methods:

Candidates:� LBNL: Eccobond 45� Genoa: Eccobond 45, silicon DC 734, Epotek353� Bonn: DC SE4445 under the MCC, DC 3140 or 3145 and a primer ASEOL

under the pigtail, 9 small dots per side between the flex and the FE’s (DC3140 or 3145)

Flex to bare moduleFlex to bare module

LBNLLBNL GenovaGenova BonnBonn


Flex to bare moduleFlex to bare moduleTo do list:� define a standard and reproducible procedure for glue deposition using

glasses, dummy flex.� verify mechanical stress coming from handling when:

åattaching pigtail and bending it;åmounting on the stave (vacuum holder).

� thermal cycles in real conditions:åC-C support and ‘final’ MS adhesive;ådummy chain modules;åreal flex;åglue on module deposited with a standard procedure.

� Effects on flex (line ruptures) or wire bonding (detachments) can bemonitored only through hot modules.

� Wire bonds uniformity: test with nitrogen flow to verify the wb’s quality,x-ray, pull-up test.

Effects on bumps canbe monitored withdummy chain modules(PCB).


Wire bonds PottingWire bonds PottingCan we avoid wire bonds potting?Main Requirements:� radiation hard;� quantity small enough not to wet the zone for the vacuum holder;Experience:� Genova: silicon DC 734 (too fluid). Some experience with optical fibre.� LBNL:� Bonn: silicon?? First trials. No firm conclusions yet.Comments:� This adhesive can be chosen after the other ones.� Problems with weak wire bonds (if any) during deposition and thermal

cycles.


Module to Carbon-Carbon supportModule to Carbon-Carbon support

This is the most tested adhesive.

Requirements:� thermal conductivity > 0.2 W/mK;� soft: shear modules < 50 N/mm2;� radiation hard;� Electrically non conductive;� curing at room temperature;� adhesive confined within the chip;� good wetting;� not creeping after curing;� allow module replacement without damaging the support.


Module-support adhesiveModule-support adhesive

Status of the adhesive test program (first part):

� CGL7018 is the current baseline:å1 component thermal paste;åits function is exclusively “thermal”;åthe mechanical link of the module on the support relies on permanent UV tags;åthe long term reliability is unknown (it is a grease, only partially cured).

� Starting with a list of 15 candidates, after two selection steps werestricted the choice to the following two:

åEccobond 45 (Emerson Cuming): 2 component epoxy (flexible mixture).åSE 4445 (Dow Corning): 2 component silicon.


Eccobond vs SE4445Eccobond vs SE4445å deposition possible with dispenser

(similar to CGL)å do not need tackså good applicability with simple masks

(tricky on the stave?)å removal is feasible only heating up to

60-70 C (test on stave done inGenoa)

å stiffer (more stress on module)

Eccobond Eccobond å very flexible: easy removal, less

stress on moduleå applicability is possible and gives

good results using calibratedglass micro-spheres

å need tacks (?)å degradation after irradiation ?

(still to be tested)

SE4445 SE4445

To do list:� Shear and creep tests on irradiated SE4445 (samples ready at CERN).� Irradiate and repeat temperature cycles on samples already temperature cycled

(Marco and Wolfgang).� Equip a full stave with dummy Si heaters glued with the three adhesive candidates

and perform an evaporative cooling test to get a final assessment of the differentthermal performances (Marseille)

� Get more experience on SE4445 application. (done in Bonn, should also done inGenova, Bonn will send spheres..).


Conclusions to the MS adhesive programConclusions to the MS adhesive program� On the basis of the results available up to now we have two alternative

options to CGL7018.� We can decide to have three candidates or we can reduce them to two

(baseline + backup).� To have reproducibility is not easy and it’s a long job (Marseille experience

on CGL): each lab can not tune its own tools for each of the 3 adhesives.� When do we have to decide????

Still to do:� Radiation effects on SE4445 (when???);� Verify effects on pixel noise/threshold if adhesive is not confined under

the chip surface (relaxing this constraint would make easier to getreproducibility).

� Next slides refer to some measurements done in Genova (Apr 00).


Effects on glass of glueEffects on glass of glueDow Corning 734RTV and Epotek 353ND have been used on glass samplesbumped on bad electronics, both glues are fluid. A minimal quantity isapplied on two edges (parallel to columns), it enters in between chip andglass by capillary effect. Dow Corning enters <0.5mm, Epotek fills almosteverything.


Effects on electronics of glueEffects on electronics of glueSmall amount of Araldit353 has been put on glass sample and on a singlechip with FE_C (GE_C_7). In both cases glue is deposited at the EoC logicedge (the only accessible for the single chip once mounted on board).

EoC logic is here

Glue enters as expected (~3-4 mm)


Effects on electronics of glueEffects on electronics of glue

3150e3150e

5000e5000e

6500e6500e

140e140e

290e290e


Threshold before and afterThreshold before and after


Noise before and afterNoise before and after


How to go onHow to go on� Take a decision on module-C-C support adhesive (3 or less candidates).

When????� Make a test program on flex–module adhesive, using the new dummy

modules to define pattern deposition and candidates as a function of thebump bonder (IZM,AMS).

� We need to verify during thermal cycles and module handlingå flex lines;å bump connectivity;å wire bonds connectivity.

� Quantify possible effects induced by the pigtail bending.� I see no priority on other adhesives (MCC-flex, pigtail-flex, wb’s potting).

� We have some experience: we need to collect it but coordinate efforts.


Towards next Pixel WeekTowards next Pixel WeekFlex module adhesive:� As a main requirement there is the possibility to have uniform wire bonds

quality. This could be achieved putting no glues under the pads (then theflex could be no flat, other difficulty for the wb’s) or putting a uniformamount of glue.

� This was an issue in Genova where we always used glue under the padsdeposited manually. Now we have a automatic dispenser, reproducibilityshould improve.

� Check the wb’s quality using:å nitrogen flow (flow to be carefully tuned to individuate weak wire bonds but

not to weaken the good ones);å pull up test;å x-rays ( available in Genova in few months).


Towards next Pixel WeekTowards next Pixel Week� Test with thermal cycles: setup

å dummy chain modules gluing on a C-C support with a final candidate adhesive;å testing flex-module pattern glue;å real flex;å no wire bonds or potting.

� Monitoring:å by probing dummy chip or monitoring signals through a board (Bonn/Genova-

AMS in this case some wire bonds are needed to the board) to check bumpconnectivity;

å by probing flex to check line continuity.


Towards next Pixel WeekTowards next Pixel WeekPigtail stress on module:� Quantify strength.� First measurements can be done with old modules: attaching the pig tail

and bending it, eventually performing thermal cycles.� We can do measurement with the dummy modules already used before

again: : attaching the pig tail and bending it, eventually performing thermalcycles.

adhesive test program - ge.infn.it · adhesive test program, dec 6th 2001 3 3 glue joints on...

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