- Sat Jan 12, 2013 4:28 am
#154127
I am climbing the Eagle learning curve and have mastered laser toner printing to the extent of producing single and double sided boards confidently with 10mil tracks without retouching and can do 8mil with luck. Even my method to get the top and bottom side print registered seems to work consistently. I am using a modified laminator for the toner transfer.
I have made a few single sided boards OK and used the liquid tinning approach which has worked ok so far.
Now I am taking the small step of a double sided board with wired components topside and some SMD caps and a couple of SOICs on the reverse. Time to try out some reflow, even though I could hand solder these few components.
I modified a toaster oven which is driven from a PID controller. After 'learning' the PID controller and testing the oven, I can get very close to the recommended ramp times.
Liquid tinning does not seem to like reflow! Rather the tinning goes from shiny to nasty grey so I guess I will have to give that up. My biggest problem now is the solder paste and its finish after reflow. I was expecting my test pieces with paste blobs to come out nice and shiney just like hand soldering. I am using a paste code SN62 RM89 AAS 85V. After reflow my solder blobs have a darkish gray film over them which does not clean off well with alcohol. It is thicker than I expected for a flux residue and 'peels' away from my test blobs like a conformal coating. By adjusting the ramp soak time I can get the coating to be harder or softer, but it still seems well stuck. the solder underneath has flowed and looks bright. I chose this lead based paste for its 210 deg C lower reflow temperature than non-lead alternatives
My question is am I using the wrong kind of solder paste, does everybody else get this kind of 'coating' and is it something I need to find a solvent for? I was hoping my test boards would reflow the solder nice and bright like manufactured boards so what am I doing wrong? I have read of others watching solder during reflow go into the 'coalesc' phase and run into a joint, but all I see is a grey spot with the solder phase hidden underneath.
I have made a few single sided boards OK and used the liquid tinning approach which has worked ok so far.
Now I am taking the small step of a double sided board with wired components topside and some SMD caps and a couple of SOICs on the reverse. Time to try out some reflow, even though I could hand solder these few components.
I modified a toaster oven which is driven from a PID controller. After 'learning' the PID controller and testing the oven, I can get very close to the recommended ramp times.
Liquid tinning does not seem to like reflow! Rather the tinning goes from shiny to nasty grey so I guess I will have to give that up. My biggest problem now is the solder paste and its finish after reflow. I was expecting my test pieces with paste blobs to come out nice and shiney just like hand soldering. I am using a paste code SN62 RM89 AAS 85V. After reflow my solder blobs have a darkish gray film over them which does not clean off well with alcohol. It is thicker than I expected for a flux residue and 'peels' away from my test blobs like a conformal coating. By adjusting the ramp soak time I can get the coating to be harder or softer, but it still seems well stuck. the solder underneath has flowed and looks bright. I chose this lead based paste for its 210 deg C lower reflow temperature than non-lead alternatives
My question is am I using the wrong kind of solder paste, does everybody else get this kind of 'coating' and is it something I need to find a solvent for? I was hoping my test boards would reflow the solder nice and bright like manufactured boards so what am I doing wrong? I have read of others watching solder during reflow go into the 'coalesc' phase and run into a joint, but all I see is a grey spot with the solder phase hidden underneath.