Electronic Tech Tips


We got lots of emails to MyStory@jameco.com this month and we've included a few of the most interesting below. James from Antioch, California suggested the most important tip was to read the Jameco newsletter, but you already knew that.


Working with SMT Components
Eco Friendly Etchant
Sharp Probes
No Solder Sucker Here
Exact Clipping

Working with SMT Components

As a professional who has worked with a lot of SMT components both passive and IC, I can safely say an ungrounded iron or work station could be a source of problems for sure. Solder and flux choices could also make a difference in the successful assembly and operation of circuits.

When working with SMT components, a solder-paste silk screen method plus a good baking in a special oven to make the paste flow works best. But for most of us working on small projects with a limited budget, angel hair solder and a fine tip iron that is ESD safely grounded is the way to go. Those new to SMD components may struggle with "tomb stoning," which happens when one end of the component is soldered and the other end pops up in the air. Here's an easy solution.

You will need to use both hands (assuming they do not shake too much) one to hold the Iron and solder and the other to hold down the passive component with a small tool or tooth pick until the iron is removed and the solder has solidified. I also find that using a high-quality solder iron and rework station are worth the cost, both for businesses and hobbyists.

Bruce Weidner
Columbus, Ohio



Alternative PCB Etchant

I thought I would share my experiences with creating quality circuit boards using household supplies as an etchant. The basic goal I set out to achieve when I started was to create a factory quality; double-sided circuit board without having to purchase ferric chloride. After many years of research I learned that a basic pool chemical combined with simple over-the-counter hydrogen peroxide creates one of the best etchants.

I set out to create an etchant that, by my calculation, would be roughly 8 times cheaper than ferric chloride. I used two common household chemicals: muriatic acid (pool chemical) and hydrogen peroxide. Anytime you decide to mix chemicals, it's a good idea to wear protective gear like gloves and goggles.

Mixing your own etchant is not without its hassle factor, but the wonderful part is that this etchant can be easily mixed on the fly in a measuring cup and only requires a 3 oz mixture to etch a 1" x 1" board in one minute at room temperature. I know that may sound unbelievable, but simply mixing 1 oz of muriatic acid with 2 oz of over-the-counter hydrogen peroxide yields one of the most economical etchants one can ever find.

Supplies:
    1. 16 oz 3% Hydrogen Peroxide
    2. 32 oz 31.45% Muriatic Acid (available from pool supply or hardware store)
    3. 150ml measuring cup
    4. Plastic TableSpoon
Recipe for a household etchant:

Wearing gloves and goggles, simply pour 50mL of Hydrogen peroxide (3%) in your 150mL measuring cup then add 25mL of Muriatic Acid (31.45% Hydrogen Chloride). Stir this mixture with a plastic spoon for a few seconds. Remember never to add the peroxide to the acid. Instead make sure you add the acid to the peroxide.


Through trial and error I have successfully timed and etched .5 oz copper clad boards (double and single sided) without an etching tank or heater in less than 2 minutes. Boards smaller than 2" x 2" can take considerably less time.

I don't recommend you make an extra supply and store it, because the moment these two chemicals combine, a reaction starts which slowly neutralizes the solution. Happy etching, and thanks for reading.

John Macklin
Wichita, Kansas



Sharp Probes

The March Jameco newsletter suggested that some might use a scalpel as a sharp probe. I've had good results using a sewing machine needle that I soldered to some wire and an alligator clip. It worked well for me. (See image below)



Manny Silva
North Plainfield ,NJ



No Solder Sucker Here

I work mostly with small boards (less than 2.0 square inches). Unless the board has an accelerometer chip on it, I find the easiest way to get rid of excess solder is to give it a sharp whack. If you heat a connection then immediately whack your hand on the bench (while holding on to the board) the molten solder will fly off and hit your work surface. It's quick and dirty and probably dangerous, but it saves me time.

Denis Lebel
Sudbury, Ontario, Canada



Exact Clipping

I've often used an X-acto knife test lead clip with my meter in order to make voltage and resistance checks on fine-pitch parts. With the clip lead attached to the back of a pointed blade, I've got the blade handle for safety and easier control, and the sharp point can make hand-probing down to < 0.5mm possible and can pierce solder mask if needed. It's also a good way to confirm I'm just about to cut the correct trace when doing an ECO.

William Burton
Houston, TX



Once again send us your tips and all your electronics stories to MyStory@Jameco.com and we'll share as many as we can.