Homebrew PCBs

----- Original Message ----- 
From: "Harvey White" <madyn@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, February 20, 2009 9:01 PM
Subject: Re: [Homebrew_PCBs] Surface Mount


> On Fri, 20 Feb 2009 20:27:33 -0000, you 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.
> 
> In theory, yes.  You might find yourself using 8 mm traces, or 10 mm
> traces and somewhat larger pins.  I inadvertently made a board with
> 0.5 mm spacing pins on one 4 pin connector, and it turned out semi
> "OK".  The whole board was a bit over etched, so the pins did not look
> as nice as I would want, but otherwise ok, I'd suppose.
> 
> You'll either want a small tip (almost a needle) soldering pencil for
> the leads, or you'll want to tin-lead coat the pads before soldering.
> Very find gauge solder is also a must.  I find that upon occasion, a
> larger soldering iron to solder multiple pins at once, and a
> desoldering tool (built in air pump kind, not spring release) cleans
> up things nicely.  NOT elegant, I know.

Drag-soldering is much quickerl.

Leon
--
Leon Heller
Amateur radio call-sign  G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller