Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!att!mcdchg!mcdphx!xroads!wiz
From: wiz@xroads.UUCP (Mike Carter)
Newsgroups: sci.electronics
Subject: Re: Surface-mount chips
Summary: IRONS and CMOS and EDDY CURRENTS
	 SMT and TELSA
Message-ID: <738@xroads.UUCP>
Date: 27 Jun 89 03:42:25 GMT
References: <465@sdcc15.ucsd.edu> <25991@amdcad.AMD.COM> <19590@cup.portal.com> <3243@kitty.UUCP>
Distribution: usa
Organization: Crossroads, Phoenix, Az
Lines: 43

In article <3243@kitty.UUCP>, larry@kitty.UUCP (Larry Lippman) writes:
> In article <19590@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes:
> > [Discussion about replacing SMD deleted]
 [[ DIscussion about bravery with an iron deleted ]]
> 	On a more serious note, I would be rather concerned about stray
> leakage currents from the soldering iron destroying CMOS circuits, since
> I don't know of any soldering gun which has grounded elements.
> 
> <>  Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.

I have heared a lot of folks say this in the past about working with CMOS and
some saying the same thing about TTL...(although they were taken with a
tablespoon of salt too..)
The only problems I have ever encountered with CMOS are:
(1) Don't discharge your 6.5 foot TESLA coil near a CMOS circuit
(2) Dont scrape your feet over a 70% nylon carpet and touch a CMOS circuit
 
Other than that, I've desoldered and resoldered miles upon miles of
jumperwire, broken traces, component leads on CMOS boards and not once have
had any other I.C's die because I worked on the board without a grounding
strap. My bench top is grounded....but I.C's dying from AC eddy's from my
iron..NO.
In fact..if this had any merit to it, all of the major and all of the minor
manufacturers and repair shops would be using other means to solder CMOS
I.C's into pcb's. SMT chips may be physically smaller in size, but the chips
(the working guts within) rarely change in physical size. Just the
packaging...
The only extra care needed with SMT is the LENGTH of time the iron sticks
around...they are more susceptable to heat dammage.
 
.....that and the uncanny ability for the SMT's to jump right out of your
hands
 and find the most conjested waste basket with the deepest and ugliest
content array.
 
Of course I'm gonna get flamed by the purveyors of scientific research and
the 500 watt soldering iron crowd....(sigh)
 
-- 
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= Mike Carter  N7GYX, Phoenix AZ| Q: Why did the Chicken cross the road  ?  =
= hplabs!hp-sdd!crash!xroads!wiz| A: To ESCape the Main Menu .              =
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