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Topic: What is Chip Quik? (Read 581 times) previous topic - next topic

ChrisTenone

Oct 14, 2016, 07:43 am Last Edit: Oct 14, 2016, 08:22 am by ChrisTenone Reason: I fixed the math and nomenclature.
I have a 'Quik Chip SMD Rework Product', so actually, I know what it is: I wanted to desolder a board, and it seemed like a good way to do it - and yep! It works as advertised!

But I'm curious! It stays molten - or at least slushy - for a long range of cooling down temperatures, after melting it with a soldering iron. It looks like regular solder, but is a lot more brittle. The purpose of this metal is to mix with regular solder, and keep it liquid for a longer time, to facilitate removing components soldered in multiple locations, like an SMD chip, or board with lots of pins. It keeps solder joints workable for 15 or more seconds. But what is it?

I've see this question asked here before. It reminds me of Wood's metal, but that contains lead and cadmium, two of the most toxic heavy metals! Surely they wouldn't sell that! So I did an experiment on the stuff in the package of Chip Quik that I bought a couple weeks ago at Fry's Electronics:

A sample of 'chip quik' solder was prepared by cutting a piece approximately 0.3mm x 0.7mm x 0.2mm with diagonal cutters directly onto a sticky, carbon film coated, sample pin, and pressing it firmly into the film. The sample was inserted into a Phenom ProX scanning electron microscope, and imaged with configurational color. The material appeared granular, with three different components. Refer to figure a:


figure a - image modified to improve readability

On the right side of figure a, is an elemental analysis of each of the grain types, obtained by Energy Dispersive x-ray Spectroscopy at 15kV. This data shows the percent of each element in the material targeted.The three different materials are:

1) A light colored material that seems to have flowed between the other grains, contracted and cracked upon freezing. This material comprises about 64% of the total. It is 79% bismuth (Bi), 16% carbon (C), and 4% sulfur (S).

2) Dark, rounded grains approximately 10 microns in diameter. The dark grains comprise 27% of the total. They appear to be an alloy composed of 62% tin (Sn), 16% Bi, 7% indium (In), 8% C, 7% oxygen (O), and 0.3% S.

3) Pinkish gray grains, about 5 microns in diameter.  These grains account for 9% of the total material. They look like an alloy made of 65% Bi, 18% In, 13% C, and 4% O.

The overall composition of the material is: 63% Bi, 17% Sn, 14% C, 2% In, and about 1% each of oxygen and sulfur. Plus or minus ... 2% ish?

The presence of carbon is more than would be expected due to physical handling, and may account for the brittle nature of the material. It may also account for the 'slushi-ness' of the semi-liquid mixture while it is in the elongated cool down stage, explained by carbonate/thionyl nucleation sites that remove cooler, solidifying, molecules. Or it could be oily contamination from the manufacturing process.

Anyway, here it is. Please interpret this data!
What, I need to say something else too?

ChrisTenone

#1
Oct 14, 2016, 09:23 am Last Edit: Oct 14, 2016, 09:24 am by ChrisTenone
Figure b, sample sites (open in new window for full magnification):


What, I need to say something else too?

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