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SMD removal. 3

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itsmoked

itsmoked

Electrical
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Check this out...
It is supposed to ease SMD component removal/rework by use of a "magic" solution that causes the solder's melting point to plunge. !!

Has anyone tried this stuff? Does it actually work?


Keith Cress
Flamin Systems, Inc.- <
 
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Yes! That was a concern to me too..
And what happens to all the neighboring parts with this stuff slopped on them?


Keith Cress
Flamin Systems, Inc.- <
 
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No magic, just a low melting alloy that alloys with and thereby lowers the m.p. of the solder.
"Chip Quik consists of a low temperature removal alloy in wire form with excellent wetting ability that melts at 136°F (58°C)."

Common Fusible/Low Melting Alloys usually contain bismuth, lead, tin, cadmium or indium. Some eutectic alloys and their m.p.'s (omitted any with Cd or Pb):

In66.3Bi33.7 72oC
Bi57In26Sn17 79oC
In52.2Sn46Zn1.8 108oC

Adding Gallium, m.p. 30oC will further lower the alloy m.p.

Perhaps someone who removes SMD's can buy the stuff, or get a free sample as offered on the website, and report the Patent No. and any MSDS info re composition.
 
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Hi kenvlach;

I guess that's what's bothering me. You have a solid material that melts at 400C.. I don't see why a material that melts at 58C would affect the high MP material WHATSOEVER. That's like saying put this molten lead against this steel bar and the steel will now melt at 400C. I don't understand. I can easily see that mixing the various alloys while they are both in liquid form would lower the MP of the final alloy.

Keith Cress
Flamin Systems, Inc.- <
 
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I ordered a sample of it, but haven't tried it. I asked for SMD removal suggestions on sci.electronics.design or (comp.arch. embedded) and got about 10 replies suggesting that I try Chipquik as it works great. I did replace an FPGA on one of my boards since I got the sample, but I wasn't brave enough to try it on such a large and critical device.

I too have wondered about the melting point. From what I remember from materials and chemistry: with heat applied the material will rise in temperature until the melting point is hit and it begins to melt. Once all of it has melted, the temperature can begin to rise again until the boiling point is reached. So, even though it melts at a low temperature, it can be heated up enough to melt solder. It probably also has a very high thermal mass and high conductivity, meaning it stays hot so that solder that it is in contact with melts and stays melted long enough to remove the device.
 
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How is this different than flux?
 
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Flux is for cleaning and wetting. Not for changing the melting temperature of solder.

I'm open to corrections if I missed a day at class.

 
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Hi itsmoked,

Think of putting salt on the road in winter.
Water melts at 32 degrees F.
Salt melts at some very high temperature.
Salt water melts at 0 degrees F.

Jim
 
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Yo Jim.

I understand that [blue]totally[/blue]. But in that case applying NaCl a dis-solvable solid onto snow.. Hmmmm on a microscopic level... The snow is solid water... What if you have 5F snow and throw 3F salt on it, does the snow still melt? How/why does the snow melt enough to allow the NaCl to start dissolving. Now you've gone and caused me more perplexity!! If this can be explained then I guess the chipquik can be.

I was rather thinking that you were flat going to have to heat every speck of existing solder up to its original temperature at least briefly enough for it to liquefy thereby allowing the alloying to be changed albeit quickly. If this supposition is correct their "remove parts at 300F" would seem misleading, as in the solder will remain liquid at lower temperatures once its melting point has been altered.


Keith Cress
Flamin Systems, Inc.- <
 
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I thought of the same issue. My best guess is since you're slathering this stuff on across many pins at once, rather than pinpointing a single pin, total heat build-up will be less. Each pin will get to the required melting point for the standard solder, create the new alloy, and allow you to quickly remove heat... this certainly beats holding an iron against a single pin and having it overshoot in temp (very easy to do on a single pin/trace).

In that regard, this makes sense to me for removal. But as I mentioned before, you would have to clean the board quite thoroughly to prevent the next solder attempt to continue creating more alloy (and killing off any industrial/military spec for the board).

Potentially useful, with care...


Dan
Owner
 
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Hi, itsmoked.
When the highways department uses salt it is often colder than the snow. In many ares the salt is stored in open front sheds.
It will eventually be at the ambient temperature. When snow is forming, both the latent heat of vaporization and the latent heat of fusion are released into the atmosphere. It is fairly common for the temperature to rise when it is snowing. A snow storm is often the end of a cold spell. At this point the snow is probably warmer than the salt.
respectfully
 
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The kit comes with a whole set of things to clean up the pads and with a syringe of solder paste, to resolder the new component with uncontaminated solder I guess. So the concerns about contamination are real.

The alloy absorbing the tin-lead? Maybe. When a part is soldered to an ENIG board, the gold just gets dissolved into the solder, even though the gold has a higher melting point than tin-lead. So maybe that the same thing happens here.

Using a syringe of solder paste to resolder a new part? Yeuk.

The process of cleaning the pads and reapplying the new solder can be more time consuming than just replacing the part the old fashioned way.
 
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As the chipquik itself melts well below 300F, isn't it just a question of a solid dissolving in a liquid?

You don't need to melt salt to get it to dissolve in water.

- or am I missing the point?

A.
 
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felixc: "ENIG" escapes me. What does that stand for?

Zeusfaber.... You might be onto something there. I hadn't thought of that! Nice comparison. I certainly don't think of a metal dissolving into a liquid. I haven't seen any re-bar dissolving in the rain but that is just the common experience. Nice.

Keith Cress
Flamin Systems, Inc.- <
 
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Sorry, it means Electroless Nickel Gold Immersion. Those pc boards with a golden finish all over. When a pad is soldered, the gold dissolves into the solder, (it isn't just covered by the solder), leaving a solder-to-nickel contact.
 
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I spent a summer working as an intern for HP, fabbing circuit boards. We only made gold boards period! I could walk through the plating line area where there were gold nuggets the size of walnuts laying on the floor, many dozens of them down an isle.

I guess I never heard the name of the process. lolo

Keith Cress
Flamin Systems, Inc.- <
 
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It's simple metallurgy: eutectic phase diagrams have lower melting points than the component elements. You're familiar with the Pb (mp 327oC)-Sn (mp 232oC) eutectic at 183oC. Well, Ga (29.6oC) – In (157oC) has a eutectic at 15.7oC. With alloyed metals of similar atom sizes and electronegativities, a ternary eutectic will be lower in temperature than the constituent binaries, and a quaternary eutectic will be even lower. This is because the thermodynamic entropy of mixing favors the liquid phase vs. the solid. So, solder mp's can be tailored fairly readily, although some elements are more expensive than others and not all solders have good mechanical properties, wettability, thermal fatigue resistance, etc. But, Chip Quik doesn't need to have any good long-term solder properties – it only has to wet and dissolve (liquid phase alloying) an existing solder into a low melting alloy.

Noway2, did you get an MSDS with the composition, or a Patent No.?

felixc, of course the concerns about contamination are real – you don't want an extremely low melting solder that melts or creeps during use!

A recent article “High-strength and High-fatigue-resistant Lead-free Solder” based upon the Sn/Cu/In/Ga system includes some metallurgy; note the Ga-In phase diagram. Within a certain alloy range, increasing In content lowered mp by 2oC per 1%In, and adding 0.5%Ga lowered the mp by 2.5oC.
A very low melting quaternary eutectic is Indalloy® 46L, 61Ga-25In-13Sn-1Zn, an alloy with mp 7-8oC, developed to replace mercury in liquid switches.
The recent 2006 TMS Annual Meeting's Symposium on “Lead Free Solder Implementation: Reliability, Alloy Development, and New Technology” included a paper “Thermodynamic Models for the Bi-Ga-In-Sn-Zn Lead-Free System.” (They studied addition of Ga to the Bi-In-Sn-Zn system).
John R. Barnes' website “Designing Lead-Free, RoHS-Compliant, and WEEE-Compliant Electronics,” with lots of information on elements and solder alloys, regulations in Europe, California, China and elsewhere, and lots of links, seems very useful:
 
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kenvlach; Thanks for the input Mr.Materials.[reading]

Can you shed any descriptive light on the molecular action that takes place allowing 300C solid to melt in the presence of a eutectic mate at only 150C before they have been combined?

Keith Cress
Flamin Systems, Inc.- <
 
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I wouldn't use the wording "allowing 300C solid to melt" since the process occurs well below 300 C. Although I haven't seen Chip Quik work, my guess is a rapid interfacial reaction dissolving/alloying the 300 C solid into the lower temperature melt.

This is similar to ladle metallurgy: Small pieces of (sometimes higher mp.) alloying element, usually as a 'master alloy' rather than elemental, are added to the melt prior to pouring the casting(s). The addition dissolves rather than melts, e.g., Si into Al(l) as an extreme case (done perhaps 400-500 C below the Si mp).
 
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