|
I plan to replace the MUX (U2530) this weekend and wonder if I can put solder mask on the guard traces between signal pins?? I would use Circuit Works CW2500 epoxy which is good to 350 C.? I cant think of any downside and it would help avoid solder shorts.? The guard traces are very close to the signal pins and shorts mean rework with solder braid.? 14 pins at this pitch are sure to get one that needs touch up.?
toggle quoted message
Show quoted text
I haven't decided yet whether I will do hand soldering or hot air.? I purchased a griddle at Walmart for $18.00 to act as a preheater and calibrated it with my IR temperature meter.? Its easy to hold the temperature around 170 C.? I will use a hand held fan to cool the board after soldering and before lifting it off the griddle so I don't temperature shock the board.? But I may loose my nerve and just hand solder the new part.? Either way, I think solder mask over the guard traces would help keep the solder from overflowing. On ?Monday?, ?April? ?23?, ?2018? ?09?:?02?:?08? ?AM? ?CDT, Chuck Harris <cfharris@...> wrote:
As I said, you must heat the bottom of the board to 100-150C.? This is well below the solder melt temperature, and cool enough that it won't damage parts.? Then when you use your hot air, you can keep its temperature throttled back to 300-350C, and you will only have to heat the joint for a couple of seconds. When you try to do all the heating and melting with just hot air at the top of the board, you have to way overheat the parts to get the solder to melt. The underboard heater doesn't have to be anything fancy, it could be a hot plate made to warm your coffee cup. I use a commercial product, which cost about $100, and has temperature control.? Search: quartz under board heater. I also use a beaker stirrer that has a temperature controlled heater.? With that I can even reflow smaller boards. A teflon coated frying pan, or griddle, would work too.. you will have to do something to throttle the heat down, and the sides get in the way. If you must use a soldering iron, use something with a chisel tip, and lots of flux.? You can wipe the tip over the leads. -Chuck Harris machineguy59 via Groups.Io wrote: ? Thank you.? I have the right jumpers in the right place.? I also found a J103 on the schematic and put a jumper on it as shown on the schematic.? The scope now powers on without incident except the trace vertical positions, and intensity knobs do not change trace position or intensity.? I am using the screen bias adjustment as an intensity control. |
