New Heat-Reduced Magnetic Solder Could Revolutionize Chip Design 103
A new heat-reduced soldering technique using magnets may lead to some revolutionary changes in the way chips are manufactured. Details are scant since the inventor seems to be playing it close to the vest for now in hopes of attracting chipmaker interest. "The result is a tin-silver alloy that contains a dispersion of iron particles tens of micrometers in diameter. When a magnetic field is applied to the solders, two things happen. First, the iron particles heat up, locally melting the solder. This localized heating, which works on the same principle as inductive stoves, remains completely contained, keeping the surrounding area cool. And second, the iron particles line up with the direction of the magnetic field, squeezing and pushing the liquid in that direction. This alignment is retained when the solder solidifies, and the well-ordered particles provide mechanical reinforcement that's greater than that afforded by a regular dispersion of particles."
Re:Wait.... (Score:3, Informative)
This would work great for individual components, and you could leave final assembly in the realm of other soldering techniques.
The only problem with that is that when you want to use two separate bonding techniques on a board, the cost and complexity skyrockets. This is why (or at least, one reason) this is traditionally avoided (the exception for that is reflow and wave soldering, which touch different component types... DIP vs. surface mount... even then though, the chemistries involved are frequently similar).
Even if you could manufacture that on the cheap, how are you going to support it? Throw away whole boards instead of rework/repair them? Some boards might be cheap enough to just throw away... but if they're that cheap, you're probably not using a fancy pants soldering technique anyhow.
Re:magnetic field? (Score:3, Informative)
Not to be pedantic, but this is the Internet... They are applying magnetic flux to their solder, not just a magnetic field. A field doesn't impart any energy.
Perhaps true, but keep in mind that in the context of Solder, "Flux" [wikipedia.org] has an entirely different meaning.
Re:What about the RF characteristics? (Score:3, Informative)
Seems to be based on core loss (Score:2, Informative)
Solder is already conductive, so the eddy current losses won't be localized in the iron particles. Further, copper traces are even more conductive.
This must be based on the hysteresis losses in the iron B-H curves. That means he's probably got a very high frequency magnetic field generator that he's using to heat up the iron. Seems like a simple principle.
That said, I still don't want iron filings in my solder!
Re:magnetic field? (Score:3, Informative)
Neither does magnetic flux. Magnetic flux is a local property of the static field and not the same thing as EM flux. It was a good pun, though.
Re:magnetic field? (Score:3, Informative)
Magnetic flux is simply the area integral of magnetic field strength. You can't have one without the other. (For the pedantic, the integrand here is actually magnetic flux density, which is proportional to magnetic field strength.)
However, for inductive heating you need a time-varying magnetic flux, which in this case is probably achieved by varying the field strength. The field can still be aligned on an axis, so the method works anyway.
No useful details in the article. (Score:4, Informative)
Quote from ScuttleMonkey, the Slashdot editor: "Details are scant..."
Neither the Slashdot editor or the writer of the linked article understand the physics. Magnetic fields cause something to heat only if the field is rapidly changing. Then the magnetic field causes everything conductive to heat, including iron particles.
Re:magnetic field? (Score:3, Informative)
You can't apply a magnetic field to a material where a field didn't previously act without having the field intensity fluctuate (flux).
"Magnetic sensitive components"? (Score:5, Informative)
When you bring a magnet near a PC, the damage is done to magnetic recording media, not the chips. Silicon is not generally sensitive to magnetic fields. This guy [magconcept.com] has managed to put a video game controllers, keyboards, and mice inside an MRI bore. If those integrated circuits can work in a 3T magnetic field, I'm pretty sure it can survive this new magnetic assembly technique.
Re:Isn't that how we make cold joints (Score:3, Informative)
It's for use with assembly line surface mount technology [wikipedia.org]
The boards are then conveyed into the reflow soldering oven. They first enter a pre-heat zone, where the temperature of the board and all the components is gradually, uniformly raised. The boards then enter a zone where the temperature is high enough to melt the solder particles in the solder paste, bonding the component leads to the pads on the circuit board. The surface tension of the molten solder helps keep the components in place, and if the solder pad geometries are correctly designed, surface tension automatically aligns the components on their pads. There are a number of techniques for reflowing solder. One is to use infrared lamps; this is called infrared reflow. Another is to use a hot gas convection. Another technology which is becoming popular again is special fluorocarbon liquids with high boiling points which use a method called vapor phase reflow. Due to environmental concerns, this method was falling out of favor until lead-free legislation was introduced which requires tighter controls on soldering. Currently, at the end of 2008, convection soldering is the most popular reflow technology using either standard air or nitrogen gas.
The researchers are proposing to replace these methods with a high-frequency oscillating magnetic field that would heat the solder to melting point