Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" 
<leon_heller@h...> wrote:
> 
> ----- Original Message ----- 
> From: "Chris Warnes" <warneschristopher@h...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Tuesday, January 20, 2004 3:33 PM
> Subject: [Homebrew_PCBs] Gas Soldering Irons as hot-air pencils?
> 
> 
> Hi Guys,
> 
> I am looking at options for a project I have underway,
> which "unfortunately" requires me to solder a 100pin TQFP surface
> mount component to a PCB (yet to be designed). There appear to be
> various ways of doing this, but the one that I think I can manage is
> using a hot air pencil. I've seen various designs modifying
> desoldering tools but being in the UK they are quite expensive -
> certainly not as cheap as £9.99 from RadioShack! I have found one,
> from Rapid Electronics which is fairly priced at around £20, but it
> is an "inline" desolder, and I am uncertain if this could be
> modified. Likewise, there is no specified power output for it, so I
> am unsure as to its suitability.
> 
> Another technique is to tack down the corners, apply plenty of 
liquid flux
> and 'flood' the leads by dragging a blob of solder along them. 
Clean off the
> excess solder with desolder braid and remake any suspect joints.
> 
> The other option I thought of is perhaps using a portable gas
> soldering iron. Rapid again sell a 70W equivalent gas soldering iron
> with a hot air tip, and I wondered if anyone has tried one of these
> to see if it works?
> 
> My other concern is that I will be manufacturing the board using the
> Resources at my University, which are just like any other "school"
> PCB manufacturing tools using etching chemicals - am I likely to get
> the "resolution" needed for etching the pads onto the PCB for this
> component using the chemical etching process or will this also be
> problematic?
> 
> If the lead spacing is 0.5 mm this could be tricky. 0.65 mm should 
be OK.
> 
> 
> 
> Leon Heller, G1HSM
> Email: aqzf13@d...
> My low-cost Philips LPC210x ARM development system:
> http://www.geocities.com/leon_heller/lpc2104.html



You did miss one option.  paste flux and the oven.

The smother, then uncover is the way a lot of people do it.

Another option is to google a little more.   I read a how-to on 
taking a standard high watt iron, adding some small copper pipe and a 
small fish pump to make your hot blow gun.

IIRC, he used steel wool to hold the copper away from the iron and 
that acted to help pick up the heat.

some small tip, probably a little beating action and you get a narrow 
tip.  Use a Tee connector on the copper to let you connect your 
tubing.  I think I would extend the tubing back along the handle and 
wrap it with some sort of insulation so as to make the plastic 
contatc a cooler place than near the tip

good luck!

Dave