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Re: Surface mount component holder



Very good tips, Assi!

It's what I used to do when I worked in engineering.  In the absence of two
soldering irons or guns, there are a couple other tricks I have used.  They
work, but obviously not as good!

1.) If you can use an iron with a wide enough tip, then sometimes you can
touch both sides of the component at the same time with one iron (OK for
resistors and ceramic caps.  Will not work with tantalum caps since the pads
don't come over the top normally).

2.) Move the iron back and forth between the pads several times in a row.
Leave it on the pad just enough to start solder reflow.  Eventually the pads
will be hot enough that both will have molten solder and you can move the
part into place.


If you want to get really, really fancy, Metcal makes special soldering
irons designed for handing surface mount components.  Probably pretty pricey
but they work really well!

Finally, one other trick I found worked (regardless of using one or two
irons) is to add a small amount of solder to the PC board pads BEFORE
putting the part down.  Put the solder down and then put the part down.
Then "reflow" the solder by using the tips you suggested.  I found that with
the shaky-ness of my hands (I could NEVER be a surgeon), I could knock the
part out of place (even while holding it with a tweezers) when trying to add
solder.

One last suggestion for bigger components with flanges and so forth would be
to use a heat gun!

Great suggestions!

73,

Jon
NA9D

on 1/26/01 12:45 PM, assib@imap1.asu.edu at assib@imap1.asu.edu wrote:

> 
> Solder in the mouth is not a good idea.
> 
> Here is how we do surface mount discrete:
> 1. Put water soluble flux on the pad.
> 2. Place the component on the pad, but do not align it. Just place it so the
> component touches the pads.
> 3. Put a little bit of solder on the solder-gun's tip (first hand).
> 4. Hold the part down with your favorite set of tweezers. Don't hold it from
> its sides, just use the tip of the tweezers to keep it from moving. If you try
> to hold it from the sides the muscles in your hand will cause it to
> shake. It's the same muscles that work against us when we do sharpshooting.
> 5. Apply the solder to one of the pads. Due to the flux, the solder should get
> sucked onto the pad.
> 6. Now that one side is tacked down, you can remove the tweezers, get some
> more solder on the tip and go for the other side.
> 7. In order to align the component properly, we used another solder gun to do
> what we call "solder reflow". Take to solder guns. One in each hand, and heat
> both pads at the same time. Due to surface friction, the component will
> "pop" into place. This technique was taught to us but Chuck Green N0ADI -
> thanks Chuck!
> 8. you are done! and only used two hands - no extra appendages needed!
> 
> BTW, we also have a fan to carry the flux fumes away. Some of my guys said it
> gives them headaches, it doesn't to me, but I guess my brain is already fried!
> Also, I make sure that the guys are well fed before they do SMD work, hungry
> people tend to shake. Pizza does it really well for students :-) (After
> extensive research it turns out that Papa-Johns is better than Pizza-Hut for
> SMD)
> Assi 4X1KX/KK7KX
> 
> --------------------------------------------------------------
> Assi Friedman, ASUSat Program
> Tel: 480-844-1458 (home)
> Tel: 480-965-2859 (Office)
> Tel: 480-965-2474 (ASUsat lab)
> Fax: 480-965-0277 (ASUsat lab)
> Email: assib@asu.edu
> Home Page: http://www.public.asu.edu/~assib
> ASUSat Page: http://nasa.asu.edu
> ---------------------------------------------------------------
> 
> 
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-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Member:  ARRL, AMSAT, DXCC, NRA

http://www.qsl.net/ke9na

"A life lived in fear is a life half lived."

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