Glue Programme Material for Berkeley - PowerPoint Presentation

Slide1

Glue Programme

Material for Berkeley

(Tim)

Slide2

Contents

Why do we need to have a glue programme?

Polling the Collaboration

First thoughts on a Programme Outline

1/9/13

Glue Programme Discussion

2

Slide3

Origins

Came out of ‘decision’ to migrate from SE4445 to ‘something else’ for module mounting during stave production.

Keep SE4445 during prototyping as there is ‘a chance’ damaged/failed modules can be removed

General consensus is that ‘something more sticky’ should be used for production

General realisation that glue choices across project are not ‘well defined’.Likes and dislikes

Reasons for choice lost in historyWhat’s Been Done ?

Attempt to elicit information by polling whole community

1/9/13

Glue Programme Discussion

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Slide4

Polling the Collaboration

1/9/13

Glue Programme Discussion

4

Request sent by e-mail to several ATLAS mailing lists… asking for input for any gluing step

ASIC

to Hybrid

Hybrid

to Silicon

Silicon

to bus tape

Silicon

to HV bias pad (if different from #

1)

Honeycomb

to Carbon-fibre face sheet

Cooling

tube to thermally conducting foam and foam to face-sheet

6 responses!

Nigel, Ingrid, Dave Lynn, Richard French, Steve McMahon & Eric

Anderssen

Most expressed ‘interest’ and/or listed recent expertise – Eric’s was the most thought provoking!

“The assembly

process dominates adhesive

selection.”

Slide5

What Surfaces are Glued?

In general, adhesives are required to join two of the following surfaces

Silicon (ASIC & sensor)

Kapton (Hybrid (solder resist?) & bus tape)

FR4 (Solder resist?) (DCDC converters/SP boards, EoS cards…)

CFRP (facesheet, honeycomb, ‘C’-channels)Kevlar (

Nomex

, N636, honeycomb)

Carbon (

Allcomp foam)Titanium (cooling tube)

PEEK (closeouts)Occasionally, the two surfaces are the same material

CFRP

facesheet

to CFRP ‘C’-channel

What about sub-components?

Face-sheet pre-

preg

, honeycombs, hybrids & bus-tapes are composites of several materials all laminated together with some adhesive or other.

My view is that these should be treated in the same was as say a sensor or ASIC in that the teams involved in their procurement/development should be ensuring that they are radiation-hard.

1/9/13

Glue Programme Discussion

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Slide6

How are Surfaces Prepared?

Good

surface preparation procedures

are essential for reliable glue jointsBut, they are notoriously difficult to define and ensure compliance to…Eg

. “abrade surface and clean up with alcohol”What grit? How much pressure? How often should the paper be changed? How deep should the surface scratches be? Which alcohol? What sort of wipe? How should the part be dried & stored? For how long is the procedure effective? Is it ‘safe’ to repeat & if so how many times,

etc

, etc..?

Online surface preparation guides

Hysol

: http

://www.henkelna.com/us/content_data/14258_LT4536_TT_Aerospace_Surface_Preparation_Guide.pdf

Distinguishes between ‘cleaning’ and ‘surface preparation’

Extensive use of chemical processes

Our parts…

Are quite delicate…

Thin sections of CFRP (<0.2mm), cooling tubes (~ 0.1mm)

Sensitive areas: silicon sensor, bond-pads, etc…

Are small / fragile making handling difficult

End close-outs, stave mounting components, etc…H

ave minimal ‘surface’Thermally conducting foam The tops & bottoms of honeycomb walls

1/9/13

Glue Programme Discussion

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Slide7

Cleaning Processes

Web-search reveals many different techniques – see graphic….

All come with dis-claimers.

Need to be satisfied any technique fulfils ALL requirements (including collateral damage)

Some

techniques may require access to specialist equipment

Try to make progress by …

Deciding which techniques are suitable for which substrates

Initiating a programme of work to identify which glues offer best chance of working with the cleaning desired cleaning regime

Talk to industry

Preparation of samples?

1/9/13

Glue Programme Discussion

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CO2 Snow??

Slide8

How Much Preparation can we Tolerate?

Suggest starting with a

web-search

D

etails of ATLAS construction (Can we find out what was

actually

done?)

similar projects (CMS, AMS),

A

erospace (NASA,ESA, …)

Electronics packaging & general industry (eg Hysol

guide)

Begins to open up assembly issues….

eg

….

If the bus tape is aggressively cleaned before lamination, how do we keep the top surface clean during stave assembly OR if the top surface is cleaned after stave assembly we need an effective procedure which is physically and chemically compatible with the stave?

1/9/13

Glue Programme Discussion

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Slide9

Surface Characterisation Techniques

Need to …

Compile complete list of useful surface analysis tools and understand which are applicable to each substrate

U

nderstand what facilities are accessible to the collaboration to characterise surfaces

Equipment in labs

Contacts with partner institutes / industry

Initiate a programme to evaluate the surface properties of different substrates cleaned & treated using the allowable procedures

1/9/13

Glue Programme Discussion

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Slide10

Measurements of Adhesive Properties

Here I’m not considering ‘Application Testing’

Hybrid-silicon peel test

Bus-tape CFRP peel testASIC-hybrid push-off test

Silicon-bus tape peel testInformation

should be available from suppliers!Many tests use ‘industry standard’ equipment

DSC, DMA, Universal Materials Testers

Identify institutes with suitable equipment & effort to collate manufacturer’s data

1/9/13

Glue Programme Discussion

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Slide11

Application Testing

Verification of ‘real life’ performance

eg

…What is the (change in) force required to pull off a 1cm2 baby silicon detector from a section of bus tape after 100 thermal cycles and 1.5xLHC dose?

What is the (change in) peel strength for the bus-tape from the CFRP face-sheet after 100 thermal cycles & 1.5xLHC dose?

What is the(change in) thermal impedance through a 1cm2 x 0.5cm thick bus tape/CFRP/foam/CFRP/bus-tape sandwich after 100 thermal cycles and 1.5x LHC dose?

Such tests are ‘expensive’

How many tests?

Ideally would like 5-10 tests of identical samples

Need to minimise (=1) process variations

Tests will involve many parts from different sources moving between different locations

Full life-cycle tracking of ALL components needs to be in place for every step at every location

Probably need to identify a few ‘simple’ tests

NB ‘Simple’ = well understood geometry, components, assembly processes, environmental conditioning & test protocols

1/9/13

Glue Programme Discussion

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Slide12

Programme Outline

I (Tim!) would be willing to coordinate the programme

Before Upgrade Week:-

Document & circulate requirements

Poll community for info on surface preparation & analysis

Hold a ½ day meeting during upgrade week

Review requirements

See who’s interested and what they can contribute

Begin to define a ‘plan’

Goal might be to have an informed choice for the SE4445 replacement by end of 2014?

1/9/13

Glue Programme Discussion

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Slide13

Backup

The e-mail I sent to the groups (1 slide)

The responses I got (3 slides)

Incomplete Glue Matrix (1 slide)A RAL “designer epoxy”.

1/9/13

Glue Programme Discussion

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Slide14

E-mail Request to the Groups

I'm trying to compile a survey of the different adhesives which are being considered for use at various stages of strip stave and petal assembly. The following list is a compilation of different gluing steps from hybrid assembly all the way through to stave core assembly.

1) ASIC to Hybrid

2) Hybrid to Silicon

3) Silicon to bus tape

4) Silicon to HV bias pad (if different from #1).

5) Honeycomb to Carbon-fibre face sheet

6) Cooling tube to thermally conducting foam and foam to face-sheet

I'd be grateful if you could e-mail me any information on any gluing experience (both good and bad!) for any of the above steps. Also, I'd be especially interested to learn if the subject of adhesives is either one which interests you or in which you have expertise!

Many thanks,

Tim

1/9/13

Glue Programme Discussion

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Slide15

Responses

Ingrid

I think that would be very interesting to join forces. 

I actually asked Luise to do a survey of what studies have been done earlier on when the

current detectors were prepared. Especially to understand what kind of radiation hardness and aging tests were done. For me it was not really clear if it is reasonable to do standard aging tests

were a humidity step is included (one cycle with higher humidity, percentage not really defined).

Did you

do something like this before

?

NigelI am interested.

For petals, we glue silicon to face sheet (or more correctly, silicon to parylene-C coating on face sheet). And we glue bus tape to face sheet.

You

could also add adhesives used inside the bus tape.

Our

experience so far:

Dow

Corning 4445 for silicon to

facesheet

: Spec has break-down field on the edge for endcap use. We have bought some and will try it. It is very expensive in the

Netherlands.

Richard FI spent from 1997 to 2003 studying polymer behavior including some glues so my expertise is more the glue structure and how to measure this such as contact angle measurements, surface measurements such as wetting effect

etc

etc.

Bottom

line is this was something I could do, have the test kit in house to access and am interested in. However I'm not sure how much to bite off here but would like to help.

Dave Lynn

BNL/Yale uses for (5)

Hysol

with 30% BN. There appears to work well although we have yet to do detailed testing. For (6) cooling tube to foam we seal the foam with hysol+30 % BN and then use CGL. We plan to move to an

Hysol

+ 30% BN only solution as the UK has had good results with this (but I have not yet seen any thermal contraction measurements). But so far we seem to have good results with the CGL (based upon camera thermal imaging) but cannot yet quantify. For (6) foam to facing, we again use

Hysol

+30% BN with good results (again only based upon thermal imaging).

1/9/13

Glue Programme Discussion

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Slide16

… and more…

Steve

McM

During our discussion on Friday I said that I would pass on the headline topics that came up in the discussion with Martin on the Thursday Pixel in Manchester. Items to be

added to the list of things to look at in the glue group.

In no particular order they were1.  Thermal conductivity2.  Loading the glues to improve TC  (Boron nitride

etc

)

3. Glass transition temperature

4. Radiation tolerance5. Pot-life6. minimum order quantity

7. Time to delivery8. Cost9. Preparation details10. Disposal at end of use

11. MSDS (datasheet safety)

12. Viscosity

13. Rework issues

14. Expansion or contraction of the glue on curing

15. Is the glue hygroscopic

16. Cure temperature

17. The temperature (value and stability) of the cure environment

18. Hardness19…….1/9/13

Glue Programme Discussion

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Slide17

… and the big one!

Eric

Anderssen

I've seen this request before, and wish the best, but what are you trying to get at?

An old trope in the adhesives business is that all adhesives are the same - it's all about how they get into the joint; their properties during application/assembly are as, or more, important than their cured properties, because they all perform similarly after cure.

When I say 'old trope' I mean old--I heard this at industry conferences back in '89, and it was common knowledge before I started attending--admittedly from companies in the business of dispensing said adhesives, but they had (have) a point.

An

adhesive joint isn't reliably predictable if you can't control how much adhesive gets there, how thick it is, or how well filleted the joints are.

The

properties of mixed 2-part systems or defrosted 1-part systems (pre-cure/dispensing) trump 'ideal' cured properties because control of application properties yields controlled cured

properties.

The

10-50% variation in 'measured cured properties' reported by various institutes are likely completely obscured by their assembly processes. That is a problem. If a syringe applied (low viscosity) thermal adhesive performs better than a screed-mask applied (thixotropic) adhesive, post-cure, is it because one adhesive is better than the other, or is it because the folk that report have better control over their process?

In

my experience, assembly process dominates adhesive selection. Not to confuse the issue, but at LBNL we either select, or modify, adhesives specifically for their characteristics during assembly.

For

example, if we want or need to use 9396, but need it to be more viscous to stay where it belongs in a joint, either we wait during it's pot-life until it becomes more viscous (partially cured), but

if

the process needs more time, we add Cab-o-

sil

(microspheres and talc) to change it's viscosity in-pot-life allowing time to introduce the adhesive to the joint. In terms of performance, there is a lot of overlap.

How

do you plan to normalize the data you request across the numerous and variable processes (and internal modification of adhesives

)?

1/9/13

Glue Programme Discussion

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Slide18

…. And one from 2 day’s ago

Tony

Affolder

ASIC to Hybrid The Tra

-duct 2902 (silver loaded epoxy) works well. It

is thick enough to screen print and has a good working life. There are a few issues with it:

It

is fairly expensive and has a 3-4 month delivery time

The cure

time is too long.  Ideally we would want something that hardens to the point that we can remove the vacuum in under 1/2 a working shift.  

So workable for 1/2-1 hour, hardened by 2-4 hours, cured in 12 hours

Hybrid

to Silicon

The

Fuller

Epolite

5313

is more problematic.  It is too thin to

screen on well.  And pre-curing to thicken isn't great. So we need an electronics-grade epoxy with the following characteristicsThick enough the screen on

workable for 1/2 hr-1 hr

cures in 2-4 hour without shrinking or expanding which

doesn't damage the silicon

radiation

hard

1/9/13

Glue Programme Discussion

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Slide19

Incomplete Matrix

Gluing Step

Adherends

Required Properties

Cure Conditions

Candidates

ASIC to Hybrid

Silicon to Au/Cu

Thermal conductivity

Electrical

conductivity ?

T ≈ 20°C

P ≈ 0barg

t ≤ 24h

 

Tra

-duct 2902

Hybrid to Silicon

Silicon /

Kapton

Compatibility with silicon

T ≈ 20°C

P ≈ 0barg

t ≤ 24 hr

 

Fuller

Epolite

FH-5313

Silicon to Bus-tape

Silicon /

Kapton

Thermal conductivity

Compliance

T ≈ 20°C

P ≈ 0barg

t ≤ 24 hr

 

SE4445

Silicon to HV bias pad

Silicon / Gold

Electrical conductivity

T ≈ 20°C

P ≈ 0barg

t ≤ 24

hr

 

Tra

-duct 2902 (?)

CFRP face-sheet to core

CFRP / (Nomex / CFRP)

Mechanical integrity

T ≥ 20°C

P ≤ 0barg

t ≤ 24

hr

Hysol

9396 (+boron

nitride)

Hysol

9309.3NA

CFRP face-sheet to Th.

Cond.

foam

CFRP / Carbon

Thermal conductivity

T ≥ 20 °C

P ≤ 0barg

t ≤ 24 hr

Hysol

9396 + boron nitride

1/9/13

Glue Programme Discussion

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Slide20

Status

A low modulus adhesive is required to bond detectors

An epoxy has been formulated at RAL

Low viscosityVery low Tg (approx

-40°C)

Very low stiffness at ambient temperatureLow tear strength above Tg (potential for reworking)

Cure currently 50

°

C for 24

hrs, should be possible to reduce this temperature

Detector epoxy -

S Canfer,

RAL

12/9/13

Slide21

Compared to SE4445…

This is an adhesive

Lower viscosity so a thinner joint should be achievable

so less material and potentially the lack of any filler is an advantage

Slide22

Properties in compression by DMA

STORAGE MODULUS MPa

Slide23

Plans

Irradiation at Birmingham

syncrotron

, hopefully OctoberMake mockups of detector on CFRP and thermally cycleTry to reduce cure temperature (by catalyst choice and concentration)Further formulation development options:

Thixotropic modifiersSilane bond promoter

Filler to increase K (but I prefer to aim for a thin joint)