[sdiy] SMT?

[harry]

Ahhh......... NO!   ;^)

"jap stacking" works very well... no conformal coating needed, but CAREFUL
foresight.  If you alternate the body / lead orientation... the bodies
mechanically
separate the leads.  You cannot short them without hitting them woth a hammer.
They support each other.

Also, the same care will make those long leads, in almost every single case...
have the
lower impedance, or be ground, or one of the supply rails.  So the "feedback"
resistor will have the long lead tied to the output... and the short one right
at the inverting input.

Now... unwanted coupling is much more of a concern with the "stack" approach.

The conformal coating was achieved in the early Japanese radios with a waxy
substance. When I asked my dad what this stuff was.. he replied "fish paste"...
but
of course you have heard some of the stories of OTHER things he said. I doubt
the
veracity of that tale... ;^)

BTW... this is not a holy war. Whatever works for you is correct... the clock is
not
going backwards, SMT is here to stay. But the driving forces are really robotic
assembly and extreme low profile. Great for a cell phone (ptooey!) but hard on
the
poor bastard who has to debug the first one.  Repairs of SMT are much harder
also...

H^) harry  (SMT = holy war NOT!    BBD = holy war.......)



Rob wrote:

> "jap stacking", as you call it, can be more of a problem than a solution if
> you don't use some sort of conformal coating or insulation..
>
> Those lil suckers can touch one another and you won't be able to easily see
> it and could destroy your project completely, taking hours upon hours of
> troubleshooting. Actually had this unfortunate turn of events happen to me
> once.. I ended up so frustrated, I tore the board down and repopulated,
> making *sure* to put all the leads in one direction and using shrink on the
> leads that were questionable.
>
> I can also only think that the polarization of the resistors standing up
> could act as little antennas. Also, too, building upward is not always an
> option either where space is a premium.
>
> OTOH, when things like this happen with smt, you just rewet the solder
> joints around where you suspect the problem is, and usually it goes away, or
> changes, then you at least know where your problem lies.
>
> BTW, rarely have I had to use anything more than a headset magnifier, but,
> with 20/400 vision, I have a built in microscope.. I just take my glasses
> off and I can see atomic activity. ;))
>
> Like I said before: smt resistors have a *huge* advantage, as do trannies,
> standard opamps, and caps (only the monos and mica caps usually are devoid
> of labeling, all the others are easily identified).. Pricewise, its
> definitely worth every bit of effort.
>
> Other ICs, otoh, I wouldn't bother with trying to make it a big issue trying
> to find a cross ref in the smt world.
>
> Anything that cuts back on drilling and snipping makes me happy. ;)
>
> So, can't we have the best of both? Or is this another religion type of
> argument?
>
> CyborgZero Technologies
> www.angelfire.com/il/cyborgzerotech
> AIM:cyborgzr0 <--- that last thing is a number
> repairs/mods/retrofits
>
> > one known in the USA as "jap stack"...  named after the billions of
> transistor
> > radios
> > sent to our shores !!! This is mounting the resistors vertically, hairpin
> style.
> > I'll bet if
> > I pick this technique I'll give the SMT a run for the money !!!