One of our customer insist on repair of solder mask even if it is pin holes or less than 0.010 sq in. area.
Based on our knowledge bank, we though of thre options, there could be many more. 1. coat the exposed area with original solder resist (from PCB vendor) and cure 2. coat with solder - hand soldering 3. coat with transparent coat of chemtronics clear coat option 2 & 3 can become cosmetic issues . We could not fine specific reference in IPC stD to this kind of repair method. Can anyone provide info on more options as well the pecific ref to IPC std. ? Ashok
Ashok: Well, your customer probably has a good reason for wanting you to send them boards without holes in the solder mask. What is their goal for the mask capabilities after you get do reworking the boards? * Cosmetic surface coat? * Performance to SM-840?
So tell me, why are you letting your supplier send you boards with holes in the solder mask? What is the cause of the these holes?
Regarding your approaches to reworking the holes in the solder mask: 1 Recoat and cure original solder mask. You need to determine: * How are you going to clean the surface prior to coating? * How are you going to get the material on the board? * How are going to cure the material at 150�C for 30 to 60 minutes?
2 Coat with solder. I don�t consider solder to be a solder mask, does your customer? I�d think of solder as solder. How do you make solder stick any place other than traces and pads?
3 Coat with liquid clear "nail polish." See 2 above.
There is no IPC standard, as such. Guidelines are:
IPC-7711 Rework of Electronic Assemblies. The procedures in this guide detail the proper step-by-step techniques, tools and materials, and cautions needed to reliably rework assembled circuit boards. IPC-7721 Repair and Modification of Printed Boards and Electronic Assemblies. The procedures in this guide detail the proper step-by-step techniques, tools and materials, and cautions needed to reliably repair and modify bare and assembled circuit boards.
An alternative to the IPC documents is the guidelines posted by Circuit Technology Center at: http://www.circuitnet.com/guides/rework_repair.htm