[sdiy] More SMT

[Scott Gravenhorst]

Dave Manley <dlmanley at sonic.net> wrote:
>On 4/14/2013 9:08 PM, dan snazelle wrote:
>>
>>
>> On Apr 14, 2013, at 11:53 PM, Scott Gravenhorst wrote:
>>
>>>
>>> This is regarding a video which depicted using a Schmartboard to solder a 64 pin 0.5 mm
>>> pitch TQFP package.  The video showed a fine point soldering tip being used and the
>>> process was to use the point of the tip to push solder already on the traces leading to
>>> the IC pins.
>>>
>>> I do not have such a soldering tip, but I did have a good quality small chisel tip (I'm
>>> guessing 3/16" wide).
>>>
>>> I first put paste flux on the Schmartboard with a toothpick. 
>Just a slime coating. Then >> I put the IC onto the board and 
>after several attempts got it lined up. It's tiny stuff >> for 
>me, so I had to use a magnifier (telescope eyepiece in my case) 
>to make sure that the >> IC leads lined up with the traces and 
>that all were going to connect properly. >> >> I taped the board 
>onto my desk with masking tape. I then taped the IC to the board 
>once >> I had it registered correctly. >> >> I then cleaned my 
>iron well and applied a very small amount of solder to the iron 
>and >> dragged it while heating both the board traces and the IC 
>pins. >> >> Of course there was a small amount of "too much 
>solder" which made bridges. >> >> I wiped and cleaned the 
>soldering iron as much as I could and re-dragged the same places 
>>> on the board. This caused solder to come out from the bridges 
>and go onto the PCB >> traces. I used the magnifier to look at 
>the solder job and it looks clean. I will "ring >> it out" 
>tomorrow to see if I need to use solder wick. >> >> -- ScottG >> 
>________________________________________________________________________ 
>>> -- Scott Gravenhorst >> -- FPGA MIDI Synth Info: 
>jovianpyx.dyndns.org:8080/public/FPGA_synth/ >> -- FatMan Mods 
>Etc.: jovianpyx.dyndns.org:8080/public/fatman/ >> -- Some Random 
>Electronics Bits: jovianpyx.dyndns.org:8080/public/electronics/ 
>>> -- When the going gets tough, the tough use the command line. 
>>> >> _______________________________________________ >> 
>Synth-diy mailing list >> Synth-diy at dropmix.xs4all.nl >> 
>http://dropmix.xs4all.nl/mailman/listinfo/synth-diy >> > > > > 
>informative post! can you explain how you taped the chip down? 
>what kind of tape? and did you put it over the chip or behind it? 
>> 
>
>There's no need to tape down the part - just put some solder on 
>one of the corner pads, and then under the microscope/magnifier 
>heat the pad and push the corner lead into place. Then tack down 
>the opposite corner and then do the 'drag solder' thing for the 
>rest. Use a lot of liquid flux. 
>
>Gets very easy after you do a few of them.
>
>-Dave
>

I was paranoid about soldering if it wasn't held down somehow.  I used masking tape.  I do agree
that it is probably not necessary since the paste flux is sticky and these boards have a heavy
solder mask that helps align the pins.




-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- FPGA MIDI Synth Info: jovianpyx.dyndns.org:8080/public/FPGA_synth/
-- FatMan Mods Etc.: jovianpyx.dyndns.org:8080/public/fatman/
-- Some Random Electronics Bits: jovianpyx.dyndns.org:8080/public/electronics/
-- When the going gets tough, the tough use the command line.