Some parts have a recommended "reflow" curve that says how fast
temperature should ramp up, and how how long the part should dwell at
different temperatures.  You can look here for an example (near the
end):

http://rocky.digikey.com/WebLib/Zilog/Web%20Data/ZHX1820.pdf

It shows a recommended max of 240 C.  I don't think the storage temp is
relevant, since this is for a short time.  Also, remember that the specs
are a guarantee.  They have a safety margin built in.  Just like people
can run PICs at 40 MHz, you can exceed temp specs a little and probably
be ok.

In my first trial, I did it the harsh way.  I preheated the oven to 450
F and stuck the part in.  It took about a minute to reflow.  Then, I
yanked it out and put it on top of the oven to cool.  That probably puts
the maximum stress on the components, but everything worked ok.  Other
folks have experimented with using temperature controllers to match the
curves, but most people just stick the parts in and get good results.
Next time, I am going to put the board in a cold oven and let it warm up
with the oven.

Another description of the process is here:

http://www.pcbexpress.com/stencils/index.php

They sell stencils that help with applying solder paste.  They are kind
of expensive at $150, but it would save some time.

Alex

> -----Original Message-----
> From: Tony Goetz [mailto:NaB25J@AOL.COM]=20
> Sent: Tuesday, July 01, 2003 3:24 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Easy-bake SMT Rocks! (pics included)
>=20
>=20
> Hey, is this method of soldering fine for the chip? I have=20
> some chips that would be alot easier to solder this way, but=20
> the datasheet says a storage temperature of up to 150*C=20
> (302*F) and the site in the original message=20
> (http://www.seattlerobotics.org/encoder/200006> /oven_art.htm)=20
> has it hotter for several minutes. The=20
> datasheet also mentions a soldering temp of 235*C (455*F) for=20
> 10 seconds. Would it be worth trying?
>=20
> A very interesting method, in any case!
>=20
> -Tony
>=20
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>=20

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