Silicone contamination

[ken2]

Anyone familiar with the control/monitoring of facilites for contamination by silicones (broad term I know, sorry)ESPECIALLY in areas where critical bonding operations take place? Any relevant standards (IEST, Mil etc.)?

 

[akat]

Couple of things :

1. Silicone (uncured) present on the surfaces to be bonded is the real problem. Zero contamination is impossible and any silicone present on the bonding surface adds to the knock down factor.

2. If you are looking to quantify, monitor the amount of silicone cntamination on the bonding surfaces: then XPS is good reliable but expensive method. There is also a new method that has shown up in recent years, using uv light and reflection data. (

http://www.photoemission.com)

Last but not the least, if your bonding substrate surface is composite, then silicone contamination is really bad and reduces the shear strength of the bond. The failure modes are different. Surface preperation by bead blasting does help, however the residual uncured silicone molecules add to the knock down factor.

I hope this helps.

AK
AK

 

[ken2]

Thanks AK, will check out the site. We have used Digesil and plasma etching as surface preps here. A verification of the surfaces for "acceptable" levels of conyamination after treatment by one of the methods you mention would be helpful in qualifying our critical bonds.

Thanks
Ken