On 02.09.2012 21:56, Gerrit Heitsch wrote: > On 09/02/2012 09:07 PM, email@example.com wrote: >> Like most HK boards, with excessive solder flowing under ground planes >> and traces, making it more difficult to desolder things, with solder mask >> peeling off, etc. This is how most of the boards look like. Japan boards >> were of top quality. Clean, flat soldered, no peelings of anything. > > Hm, I know the kind of board you are refering to. They usually have a light > green solder mask while the others do have all kinds of other colors. But > to me this looks like only one specific maker and I only have one of their > boards, all others in my collection are of good quality and, from what's > printed on them, from all kinds of makers. The sticker on the expansion > port bracket always says 'HKC' though, which I read as 'Hong Kong'. I also know that kind of boards. I wouldn't say the PCBs are low quality, they were just made with a different process which is more sensitive to wrong temperature in wave soldering or something like that. The difference is in the surface of the traces prior to applying the solder mask. The older ("better") boards have blank copper traces which are then covered by the stop mask. There is no tin, lead/tin or solder layer between the copper traces and the stop mask! Nowadays, this is the preferred process because it saves you money if the tin layer is only present on exposed contact areas. During wave soldering, it is almost impossible for the wave solder to get between copper and solder mask. The other boards have a tin or tin/lead layer applied to the copper before applying the solder mask. During wave solder, if the temperature is too high, or contact time too long, the tin layer will melt and excess solder can flow into this layer, giving the effect we all know. I think there is also an advantage of the tinned boards. If you have a leaking capacitor, the alkaline electrolyte will attack the solder mask and the copper traces readily. The tin layer will protect the copper trace so there will be no or less attack to the copper. Nicolas Message was sent through the cbm-hackers mailing listReceived on 2012-09-03 16:00:32
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