Glue Programme (Tim)

Origins Came out of ‘decision’ to migrate from SE4445 to ‘something else’ for module mounting during stave production. General realisation that glue choices across project are not ‘well defined’. – Likes and dislikes – Reasons for choice lost in history What’s Been Done ? – Attempt to elicit information by polling whole community 10/07/2013Glue Programme2

Request 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 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 10/07/2013Glue Programme3

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 ? Nigel – I 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 F – I 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). 10/07/2013Glue Programme4

… 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 were 1. Thermal conductivity 2. Loading the glues to improve TC (Boron nitride etc) 3. Glass transition temperature 4. Radiation tolerance 5. Pot-life 6. minimum order quantity 7. Time to delivery 8. Cost 9. Preparation details 10. 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. Hardness 19……. 10/07/2013Glue Programme5

… 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)? 10/07/2013Glue Programme6

Gluing StepAdherends Required Properties Cure Conditions Candidates ASIC to Hybrid Silicon to Au/Cu Thermal conductivity Electrical conductivity T ≈ 20°C P ≈ 0barg t ≤ 24h Hybrid to Silicon Silicon / Kapton Compatibility with silicon T ≈ 20°C P ≈ 0barg t ≤ 24 hr 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 CFRP face- sheet to core CFRP / (Nomex / CFRP) Mechanical integrity T ≥ 20°C P ≤ 0barg t ≤ 24 hr Hysol 9396 Hysol NA CFRP face- sheet to Th. Cond foam CFRP / Carbon Thermal conductivity T ≥ 20 °C P ≤ 0barg t ≤ 24 hr Hysol boron nitride 10/07/2013Glue Programme7

Conclusions …. So far In general a poor response – atlas-upgrade-itk-strip-modules (108) – atlas-upgrade-itk-engineering (???) – 6 replies… General ‘interest’ in the problem but no ‘real’ work to establish reasons for pre-existing choices – If anything, the work done in ‘old’ WP4 materials on adhesives is almost all there is! Next Steps… – Think a little about Eric’s response – i.e. how is just as / more important than what – Define a programme to establish a baseline for missing areas 10/07/2013Glue Programme8