>>>> One question that I have is whether or not the corrosive properties still exist after cure or does the corrosive nature take place only during the vulcanizing process. As usual, it depends. The cure process can go on for a very long time before completion, if it completes at all (although most of it should happen in a few days). This depends on lots of factors, including material mass and volume, ambient humidity, etc. I think it would be unwise to expect any acetoxy RTV to be completely non-corrosive after a few days, or even weeks or months. Peter -- -------------------------------------------------------- Peter Swanson [log in to unmask] INTERTRONICS http://www.intertronics.co.uk Tel: +44 1865 842842 Oxfordshire, England INTERTRONICS is dedicated to providing quality material, consumable and equipment solutions to the high technology, high performance assembly industries, incorporating outstanding levels of technical support and customer service. -----Original Message----- From: Kasprzak, Bill (sys) USX [mailto:[log in to unmask]] Sent: 20 December 2004 19:47 To: 'TechNet E-Mail Forum'; 'Peter Swanson' Subject: RE: [TN] RTV potting materials Peter, Thank you for the nice categorical breakdown of RTV. It is certainly an area that has been taken for granted because "we always do it that way". I'll certainly be more aware of intended applications and be more selective. One question that I have is whether or not the corrosive properties still exist after cure or does the corrosive nature take place only during the vulcanizing process. Bill Kasprzak Moog Inc., Systems Group, Process Engineer -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Peter Swanson Sent: Monday, December 20, 2004 1:03 PM To: [log in to unmask] Subject: Re: [TN] RTV potting materials There are a number of different types of RTV silicone cure mechanisms, all of which give off a by-product upon curing: 1) Acetoxy - by-product of cure is acetic acid, not normally used in the electronics environment because of corrosivity. Quick cure, and the stuff you normally get to seal your shower at home. 2) Amine - cyclohexylamine (a building or construction grade product) 3) Oxime - methylethylketoxime 4) Alkoxy - commonly a mixture of methanol and ethanol These two are used in electronics, can be called "neutral" cure. The oxime types, like the Dow Corning product mentioned, can react with copper - check this. 5) Acetone - acetone This latter one is a newer variety, and seems to offer a lot of promise, because the very small amounts of acetone given off are non-corrosive, non toxic, not very smelly and they cure pretty quick. Peter -- -------------------------------------------------------- Peter Swanson [log in to unmask] INTERTRONICS http://www.intertronics.co.uk Tel: +44 1865 842842 Oxfordshire, England INTERTRONICS is dedicated to providing quality material, consumable and equipment solutions to the high technology, high performance assembly industries, incorporating outstanding levels of technical support and customer service. -----Original Message----- From: Phil Nutting [mailto:[log in to unmask]] Sent: 20 December 2004 16:25 To: [log in to unmask] Subject: Re: [TN] RTV potting materials Dave, We currently use Dow Corning 737 Neutral cure RTV for bonding many large components, capacitors, inductors, etc., to circuit boards and chassis parts. The acetal cure of many RTVs stinks, but more importantly is the fact that it creates acetic acid as it cures which can etch bare copper... that could be bad. The neutral cure stuff has little of no discernable odor. I'm sure GE makes a competitive product. Phil -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Roach, David Sent: Monday, December 20, 2004 11:15 AM To: [log in to unmask] Subject: Re: [TN] RTV potting materials We currently use an alcohol-based RTV silicone (Dow 3145) to adhere some tall through-hole capacitors to the PCB to improve vibration resistance. Is anyone aware of any water-based RTV silicones that are PCB firendly that would work as well and not have the odor while curing? Dave Roach Trane Controls St. Paul, Minnesota --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------