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Re: For the coiler who has everything else? (fwd)...SMD (fwd)

---------- Forwarded message ----------
Date: Mon, 02 Jul 2007 19:20:23 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: For the coiler who has everything else? (fwd)...SMD (fwd)

I build boards with SMD components at work (where board real-estate is a 
serious cost concern). I always start the proto board with their larger 
cousins. It's important to get it right the first time. Once the SMD 
board is built, replacing and even troubleshooting can be a challenge 
simply due to it's size. There are irons designed for several standard 
SMD packages, but each iron tip is specific to a package and it quickly 
gets expensive.

When it comes to coiling or other "hobbies", I personally would not use 
SMD components unless I couldn't find it's larger cousin.

Tinning the smd pad is important. Use thin solder and keep the heat 
down. SMD's are designed for solder paste where a template in stainless 
steel is placed over the board. Holes in the template cover only the 
pads. A paste is applied. The template is then removed and the board 
travels to a robotic system which grabs the components and places them 
in their locations. The solder paste is termed "paste" for a reason. The 
component literally sticks to it. The board then travels through a heat 
system which heats the solder paste and effectively solders the 
components to the board pads. The board then travels to the through hole 
room where any through hole components are then inserted and wave 
soldered. This process works great for smd components.

I can actually see a product here. A paste and heat machine for proto 
smd boards.

But if you have to replace a component for some reason on a workbench 
(and you will), even the smallest pointed tip using a nice Weller 
station is a real challenge. You'll find out just how steady your hand 
really is. Chips are easy but those little 603 resistors and diodes are 
a bear.

Helpful tip: When removing a bad smd chip. Use an exacto knife to cut 
through the lead (right next to the chip). Remove the chip and then 
desolder the remaining leads. This prevents accidental lifting of the 
pads. Remove excess solder and add a new level of solder. Install the 
new chip with typical soldering technique.

Take care,

Tesla list wrote:

>---------- Forwarded message ----------
>Date: Sun, 1 Jul 2007 22:44:30 -0700 (PDT)
>From: Brett Miller <brmtesla2@xxxxxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: Re: For the coiler who has everything else? (fwd)...SMD
>Well, I'm 32 but with my glasses I guess I make the
>cut.  Just slightly tin your pcb on both sides where
>the SMD component is about to go, then use your left
>hand to hold down the little chip component with a
>wooden toothpick.  In your right hand use your Weller
>12w soldering pencil and heat up the component on each
>side.  They come pre-tinned anyway.  I've just used a
>little lens for magnification...but I've only dabbled.
> I'd like to work more with SMD and learn more about
>finding the parts fast and assembling my parts list. 
>I just tend to know more about finding leaded
>components due to experience...nowdays the digikey
>search engine makes that stuff easy though.  
>Some guys have done some amazing stuff with SMD and
>solid state for micro mini sstcs and drsstcs.
>>     As for SMD's, all it takes is 20-year old eyes
>>and steady hands and a good 10 power binocular
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