Dylan Smith wrote:
> On Fri, 20 Feb 2009, jerrytr2.com wrote:
>
>> One part I scrounged is the same package as the 24FJ256GB106
>> processor I'm planning to use - a 64-pin TQFP. Good LORD those pins
>> are small. Can Toner Transfer make boards this tight? According to
>> the spec sheet, the pin pitch is .5mm, or about 20 thousandths of an
>> inch. So the traces need to be 10 thousandths of an inch, and will
>> only have 10 thousandths of separation. Ouch.
>
> 10/10 is not too difficult, one of my first toner transfer PCBs were
> 10/10. I've since got down to 8/8 (for 0.4mm pitch LQFP).
>
> I find hot air and solder paste does the easiest/neatest job when
> soldering SMD.
>
>
Do you apply a continuous trail of solder paste along each row of pads
of a quad plat pack IC ? If so you you use a syringe to apply the paste ?.
I found it easier to just use solder wire and dragging the iron across.
There are many videos on the net showing this method.
For all small SMD parts (resistors, caps, transistors,...) I found
trying to apply paste to individual pads by syringe was waste of time.
It was much easier to:
1) tin all pads using a soldering iron and 0.5mm solder wire.
2) use tweezers to lay all components on the board in approximate location.
3) apply liquid rosin flux over the whole PCB.
4) use two soldering irons to simultaneously maneuver the component and
melt solder of each pad.
For desoldering large ICs I use a cheap electric hot plate from a
kitchen shop. I place layer of glass cloth followed by the PCB. I get
the PCB to 100 ~ 150C and then hot air gun on top to desolder the IC in
question. Lifts off in a breeze, without any collateral damage.
Double sided heating like this is much less heat stress.