Hey folks! Happy Friday!
I've had excellent luck putting down fine-pitch (208 QFPs) regularly
using a mini-wave soldering tip (1121-0490-P5) on a Pace solder station.
If you are unfamiliar with these tips, they're shaped like a horse-hoof
and work on the principle of solder surface tension to hold a small bead
of solder to deposit exacting amounts on each joint automatically. With
liberal use of a flux-pen and a bit of practice, you can get absolutely
perfect "toe-heel" filleting on all of the joints down the line, and
have a 208 pin part attached in about 90 seconds or so. With a bit MORE
practice, you can also rework/break solder bridges using ONLY the tip of
the iron - very rarely do I ever pull out my wick any more, and there's
far less chance for damage. The station also has built-in hot air reflow
which I use for putting down all of my passives with solder paste when
prototyping. We use EFD's paste, and for general soldering applications
I've found the 325-500 mesh size works best.
For a while Pace had a bunch of demonstration videos on their
website of different rework techniques as well as technical documents
which described what you were seeing in detail as well as a
cross-reference to their part numbers for each, though they seem to have
restructured the site lately. Regardless, Pace's products in soldering
stations and hot-air reflow are the best I've worked with yet and I'm
happy to give a recommendation. Like anything else in this business, you
definitely get what you pay for.
For stereo-microscope, we have a made-for-SMT-work ScienceScope
SZ-BD-B2 long-boom scope with incandescent fiber illumination ring, and
it's the best money we've ever spent on anything to help the quality of
assembly and rework, aside from probably the soldering iron itself. In
the past five years I've only had to change the lamp twice, and (for
those in the US) replacements are actually available locally at Granger
in a pinch.
Regards,
-- Matt
Dennis Saputelli wrote:
> i have tried this paste and air method also and as i wrote i gave it up
> and found hand soldering with an iron to be easier, faster and better
>
> plus paste goes bad so quickly and if you refrigerate it you need to let
> it warm up
>
> but if there are several parts it may start to pay off to use the
> air/paste method
>
>
> Dennis Saputelli
>
>
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> Phillip Stevens wrote:
>
>> I have a Madell 850 which I think is similar to the Hakko.
>> They are running a moving sale on them right now:
>> http://www.madelltech.com/Movingsale.html
>>
>> They have some low cost ovens too.
>>
>> Related to this has anyone tried one of the toaster ovens? :P
>>
>> I experimented with some prototype stencils on a 208 pin QFP,
>> but ended up with solder balls between the pads and shorts under
>> the part between the pins.
>>
>> My technique now is to tack the part down on the pads, making sure
>> it is aligned. Then to run a thin bead of solder paste (OK dispensing
>> gun and one of the green size nozzles) just in front of the row of pins
>> I want to solder. Then run the hot air gun slowly down the row of pins
>> and reflow the solder letting the hot air station push the solder
>> paste towards the pins. Then solder wick up any excess solder. Touch
>> up any pins that didn't pick up enough solder.
>>
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