Graham, Try EOS/ESD Society Advisory Docments WIP2.2- Garments Field Attenuation. This eill cover test procedures for determing the electrostatic field attenuation of garments. This society has a home page: http://www.eosesd.org Let me know if you need more help. Richard Haynes 609-497-4584 -----Original Message----- From: Graham Naisbitt <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: Friday, October 16, 1998 12:43 PM Subject: Re: [TN] Confomal coating adhesion >Dear Mary and Paul, > >Interesting comments. > >Also I have found de-wetting and adhesion to be two separate issues. >De-wetting, as you describe, is the effect seen when the coating is in a >liquid form, before cure. We see de-wetting issues mainly with silicone >contamination prior to coating. > >Adhesion is when the material is cured. In this instance a low surface >energy of the coating is a bad thing and will lead to bad adhesion. > >Thus optimum is a low surface tension before cure, and a high surface energy >after cure. > >In this respect I don't agree with 'the lower the better' in terms of both >requirements (no de-wetting and good post cure adhesion). > >As an example, a silicone conformal coating will wet just about anything, >but it does not adhere well to a PCB surface. It may pass a cross hatch >test, but only because the tape won't stick to it either! Silicone coatings >are often flexible enough to induce only very low stresses from TCE mismatch >throughout the life of the board, and the low adhesion therefore doesn't >manifest itself as delamination. > >We have done several studies of adhesion and de-wetting, and the issues >involved range from free silicones (from heat transfer compounds, buffering >materials and even mould release agents from component case moulding) to >levelling agents in high gloss solder masks. Flux residues and reflow >profile can also impact on localised adhesion. > >The result of our work is an adhesion modified coating material with no >degradation in terms of wetting ability. > >In terms of thin edge coverage, application procedure is the key. Paul do >you dip or spray? I have notes for optimising your application to minimise >these effects if you wish to contact me off line I can mail them to you. > >Best Regards. > >Alan Brewin >Chief Chemist - Concoat Ltd. > >-----Original Message----- >From: Davis, Mary <[log in to unmask]> >To: [log in to unmask] <[log in to unmask]> >Date: 12 October 1998 17:54 >Subject: Re: [TN] Confomal coating adhesion > > >>We found that success in wetting plastic packages very much depends on >>the conformal coating material. Assuming the packages are clean and >>free of oil and mold release, wetting is a function of the surface >>tension of the coating material and the critical free energy of the >>substrate. Some coating products have the appropriate surface tension >>for plastic substrates, some do not. Talk with your coating manufacturer >>and try various products. Do not assume that what worked elsewhere will >>work on plastic. Some plastics have very low critical surface free >>energies - in the range of 18-40 dyn/cm. Ask your coating manufacturers >>if they can tell you the surface tension of their coating products. The >>lower the better. If the surface tension of the coating is less than >>the critical free energy of the solid, complete wetting will occur; but >>if the surface tension is greater, partial non wetting can result. >> >>Call me and I can tell you the name of the product performed best in our >>application. >> >> >> Mary Davis >> Sr. Material & Process Engineer >> Product & Process Analysis Lab >> >> Raytheon Systems Company >> Naval and Maritime Systems >> KW 281, MK4C08 >> 6500 Harbour Heights Parkway >> Mukilteo, WA 98275-4862 >> 425.356.3311 >> 425.356-3185 fax >> >>> -----Original Message----- >>> From: Paul Stolar [SMTP:[log in to unmask]] >>> Sent: Monday, October 12, 1998 7:09 AM >>> To: [log in to unmask] >>> Subject: [TN] Confomal coating adhesion >>> >>> Does anyone have any good experience at improving conformal >>> coating >>> adhesion to plastic packaging? >>> >>> Is it a cleanliness issue, or is it inherent in materials? >>> >>> ################################################################ >>> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV >>> 1.8c >>> ################################################################ >>> To subscribe/unsubscribe, send a message to [log in to unmask] with >>> following text in the body: >>> To subscribe: SUBSCRIBE TechNet <your full name> >>> To unsubscribe: SIGNOFF TechNet >>> ################################################################ >>> Please visit IPC's web site (http://www.ipc.org) "On-Line Services" >>> section for additional information. >>> For technical support contact Hugo Scaramuzza at [log in to unmask] or >>> 847-509-9700 ext.312 >>> ################################################################ >> >>################################################################ >>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >>################################################################ >>To subscribe/unsubscribe, send a message to [log in to unmask] with following >text in the body: >>To subscribe: SUBSCRIBE TechNet <your full name> >>To unsubscribe: SIGNOFF TechNet >>################################################################ >>Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section >for additional information. >>For technical support contact Hugo Scaramuzza at [log in to unmask] or >847-509-9700 ext.312 >>################################################################ >> >> > >################################################################ >TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >################################################################ >To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: >To subscribe: SUBSCRIBE TechNet <your full name> >To unsubscribe: SIGNOFF TechNet >################################################################ >Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. >For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 >################################################################ > > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. 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