Removing TQFP/TSSOP etc is very easy to do. Use a brand new razor knife and
carefully cut the leads where they enter the plastic body of the chip. About
5-10 gentle cuts per side is enough to cut through the leads and the chip falls
out. Then use a low temp iron and remove the bits of leads remaining.





BR Clive









[EMAIL PROTECTED] on 04/09/2003 09:38:39 AM

Please respond to "Protel EDA Forum" <[EMAIL PROTECTED]>

To:   [EMAIL PROTECTED]
cc:    (bcc: Clive Broome/sdc)

Subject:  Re: [PEDA] Prototype Assembly House



An easier method for doing this hand-soldering is to use what is known as a
mini-wave tip. It's a concave cupped tip that you fill with solder, and use
exactly as you describe - drag it along the pads. If the pads have been
designed right, it's really easy to do. Even without any special allowances,
it's fairly easy to do. I have no trouble with any TSSOP/TQFP/whatever that
I've tried. Make sure you put a liberal layer of flux along the pads you are
to solder, though.

I also do 0402 components by hand sometimes, and regularly do 0603
components. All without visual aids, although we do have stereo microscopes
available if required. SMT is not all that hard, and in fact I'd venture to
suggest it's less of a PITA than through-hole technology. Especially for
rework - it's much easier to remove 0603 components than it is to remove
through-hole components. TQFP devices are another story, of course...

Cheers,
Matthew van de Werken - Electronics Engineer
CSIRO Exploration & Mining - Gravity Group
1 Technology Court - Pullenvale - Qld - 4069
ph:  (07) 3327 4685     fax:  (07) 3327 4455
email:  [EMAIL PROTECTED]
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> -----Original Message-----
> From: Jon Elson [mailto:[EMAIL PROTECTED]
> Sent: Thursday, 4 September 2003 8:54 AM
> To: Protel EDA Forum
> Subject: Re: [PEDA] Prototype Assembly House
>
>
>
>
> Bagotronix Tech Support wrote:
>
> >>I can solder 0.5mm (19.685 mil) SMT IC's by hand no
> problem. BGAs are a
> >>
> >>
> >different story...
> >
> >I can do that too.  And my hand can slip, causing a solder
> bridge to an
> >adjacent pin.  It's a PITA to clear away that solder bridge
> from those small
> >pins.
> >
> >
> I have developed manual techniques to do these, and they work quite
> well.  I'm
> still fine tuning it, but I'm doing pretty well with it.
>
> What I do is manually squeeze out a VERY fine line of solder
> paste with
> standard
> syringe and a fine needle with the point ground off.  I lay this line
> around the
> outer perimiter of the component pads.  I then place the chip with
> tweezers, and
> solder 2 diagonal corner pads.  I then inspect the alignment on all 4
> sides, and walk
> the chip, if needed, one pad at a time.  When all 4 sides have their
> pads aligned,
> I just slide the soldering iron down the rows of leads, at a rate of
> about 2 pads a
> second.  If the right amount of solder has been deposited,
> there are NO
> bridges.
> If too much solder paste was applied, you will get bridges.  The best
> way to fix
> them is to remove some solder with fine desoldering braid
> that has been
> dipped
> in liquid rosin flux.  Then, you heat both leads at the same
> time, and
> the rest of
> the solder will pull into the pad/lead area, breaking the
> bridge.  (If
> the bridge is
> small, reheating the two leads simultaneously may clear it
> without the
> braid.)
>
> I then apply isopropyl alcohol to an old toothbrosh, and
> brush the leads
> vigorously,
> and wash in water from a sink sprayer nozzle.  It looks professional,
> like mass-
> produced boards.
>
> >Oh, how I long for DIP and 50mil SMT packages.  I figured it
> out - it is
> >possible to put an ethernet chip into a 28-pin package (with
> an 8-bit wide
> >uP interface).  So why doesn't anyone do it?  They have 100+
> pins.  Phooey!
> >
> >
> >
> Yup, but the old days had entire boards covered with DIPs to
> do what I
> can do now
> with ONE very pedestrian Xilinx Spartan chip.  And, if there
> is an error
> (there is
> ALWAYS an error or two) I can fix it in the configuration of
> the FPGA,
> and don't
> have to even hack a trace on the board, most of the time!
>
> (Of course, there was that one time I used a Protel PCB library part
> without checking
> it, and found out that Xilinx used a different convention
> with regard to
> pin 1 being on
> a corner or center of the side.  That one I couldn't fix with even a
> complete config.
> change!)
>
> Jon
>
>
>









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