Jorge > 1) Prior conformal coating I need wash the board, but there is 6 SMT > photo sensor and more than 20 LED , what cleaning method should I use in > order to not damage or affect performance of this components ? It MAY not be necessary to clean the boards, but you MUST get your process under good control. If you do feel the need to clean - which is undoubtedly the safer option, then I would need to know the volume of assemblies you have to process before giving you an answer as to the cleaning process you should consider. > 2) What level of DRY the board should be before coating, the > LED are heat > sensitive and could not be exposed to high temperatures for baking ( more > than 125 degree C ), what baking set up should work ? If you have a good cleaner, then it should not be necessary to bake the assemblies before coating. If you need to, then 6 to 8 hours at 80DegC should be fine. > 3) What kind of conformal coating should I use for spray application ( > acrylic, epoxy,silicone or polyurethane ) , the board environment will be > exposed to 74 degree Celsius in a sunny day ( air temperature inside the > box ) First, I should inform you that the most likely temperature inside a box exposed to the sun will be nearer 95DegC. The easiest / most forgiving material you could use would be an acrylic coating - and it will give you all the protection you could require UNLESS there is something you have not told me? Application would always be better by dipping. However, I assume that you have lots of components all over the assembly that you do not want to coat so spraying will be cheaper (less labour for masking and de-masking). Selective coating will be good, but your investment will be around $40K. > 4) The photo sensor and LED should not be conformal coated, what kind of > masking should I use, for spray coating. Use a peelable latex temporary masking compound. Better results will come from a natural latex than a synthetic. > 5) In the back side of the board ( there is no component in > this side ) a > heat sink will be attached, and no conformal coating should be > applied since > this heat sink will be in contact with a sheet metal, but the heat sink > covers about 30% of area in the bottom side, It is OK to leave the bottom > side without conformal coating since there is no components at > this side, or > should I mask the conformal coating and then attach the heat sink after > conformal coating was applied ? Now you tell me! Should have read this message first before replying! Well, first off the coating if applied correctly, will not be a good thermal insulator - only around 0.002" or 50 microns thick. Maybe this will be OK with no masking? However, with no components, and some masking on the top-side, I would strongly recommend spraying top-side only. > Thanks for any advice at any question. > > Jorge Santana You are welcome, I hope this helps. Visit my web site for much more info. Regards, Graham Naisbitt [log in to unmask] www.concoat.co.uk <http://www.concoat.co.uk> For instant access to Product Data Sheets register on the Tech-Shot area of www.concoat.co.uk <http://www.concoat.co.uk> Concoat Limited Alasan House, Albany Park CAMBERLEY GU16 7PH UK Phone: +44 (0)1276 691100 Fax: +44 (0)1276 691227 Mobile: +44 (0)79 6858 2121 --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------