How many times has this happened to you, your working on that new project in the latest QST when POP, you release all the smoke out of that hard to find IC that took you 3 weeks to get mail order?
Well fear no more, here’s how you can replace the smoke in the IC and get your project back up and running.
First a little background. When IC’s are manufactured there is a certain amount of semi-conducting smoke added to facilitate the proper operation of the IC’s design parameters. Look on any IC and you’ll notice a notch or dimple located on the edge of the chip, this is not only used to identify the position of the number 1 pin, it’s also where the smoke is inserted during the manufacturing process.
Armed with this knowledge and with the help of a common Ink Refill kit sold for color Ink Jet printers, you can replace the smoke and restore the IC back to proper operating condition.
Here is a list of what you’ll need ahead of time.
You’ll need a small workbench vise, the hypodermic needle from an Ink Jet refill kit, a 2oz. tube of Big Johnson Fill-A-Crack Gel®, a small drill bit, and a can of liquid semi-conducting smoke (available from Radio Shack, PN# OICU812).
Let’s work with a very common IC, the 555-timer.
First remove the chip from the circuit and clamp into a small workbench vise. Next locate the dimple or notch and using a small drill bit, drill into the IC. Note that you’ll only want to drill to a depth of 1/64 of an inch.
Fill the hypodermic with the liquid smoke and set this aside for now. You’ll need to look in the data sheet for the proper amount of smoke to replace in the chip. This is very important because not using the exact amount recommended by the manufacturer may cause the chip not to operate as designed. An example of this would be adding too much smoke in the 555 would cause it to operate as a 556 dual timer IC.
For my test IC, I found it requires 2gms of smoke to operate properly. Carefully inject the required amount of smoke into the IC while being careful not to breath any of the smoke as the Surgeon General has determined that smoking IC’s can cause cancer and lead to low birth weight in babies.
When you have the proper amount of smoke in the IC grab your Big Johnson® and smear the gel around the orifice (of the IC). Allow a minute for the gel to start curing and carefully remove the hypodermic from the hole while keeping pressure applied to the gel while it hardens. If your finger becomes stuck in the gel, simply use an Exacto knife to remove the top few layers of skin from your finger thus freeing the IC.
Let the IC sit over night to allow the gel to completely setup, then re-install into your circuit and test. If you find that the IC is still not working properly, repeat the above process until you get it working.
This method can also work with diodes and transistors, but resistors and capacitors require a different type of smoke as they are not semi-conducting devices. Radio Shack sells this type of smoke as well
