Quote:
Originally Posted by chaps2018
I had no idea tin lead solder was even available. Sure enough you can still buy it.
IIRC the PC industry switched over nearly 2 decades ago.
The Hengs fan had to be assembled with lead free. Some joints I added more, some I removed/replaced.
The some of the leads were so corroded the solder would not wet to them. I didn’t have any flux with me, but I will put some in my kit for next time. I will try that before removing components. :-)
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{RANT}
Yes, the Reduction of Hazardous Substances (RoHS), was forced on the world by bureaucrats at the European Union in 2006 with plenty of notice. My understanding it that the decision was made by bureaucrats, not technical people. They had heard that children's development suffered when they consumed large quantities of lead-paint chips, so everything containing lead had to be banned or strictly recycled. (Of course, lead paint was banned back in the 1970s.) This completely ignored the fact that lead (in its pure state) is very inactive. It doesn't want to combine with nearly anything. We've all grown up crimping split-shot weights on our bobber fishing poles and don't seem to be harmed.
But there are no perfect substitutes for Sn/Pb solder. The lead makes it ductile, and shock or vibration will crack a joint. In the first few years after its introduction, smartphones were so delicate that a short fall would ruin them.
And you might have heard of Mark Saylor, a California Highway Patrol officer who took his family on a Lexus test drive. The Lexus had a so-called "throttle-by-wire" accelerator. The throttle pedal rotated a potentiometer (like a volume control) and the engine computer used this signal to decide how much gas and air to feed the engine. When the solder joint failed, the computer interpreted it as Wide Open Throttle. There was no ignition key in this car (proximity fob) the driver did not know how to stop the vehicle. As the officer was trying to maintain control, a passenger phoned 911 and the saga was recorded. All four passengers died. Since that event, at least 93 people died due to the Toyota lead-free solder accelerator design.
Source:
https://www.nytimes.com/2010/09/19/b...s/19autos.html
Toyota ultimately paid a US Department of Justice fine of $1.2 Billion for and recalled 8 Million vehicles over this design.
Source:
https://www.washingtonpost.com/busin...572_story.html
Source:
https://www.transportation.gov/brief...d-acceleration
But that isn't the only well-known incident. Modern, dense integrated circuits (ICs) may have thousands of connections. A common practice is to create an IC on a silicon surface with transistors on one layer, and several layers of interconnections above that. On the top surface is a solder ball for each connection. The IC ("chip") is turned over and placed upon a "substrate", originally ceramic, with metallic plating, and heated until the solder balls melt and the chip bonds to the substrate. Interconnects go clear through the substrate and end in more solder balls on the other side. The top and side of this assembly are "encapsulated" to keep moisture out. This assembly, called a ball-grid array, is placed on a matching pattern on a printed circuit card and once again heated until the solder reflows.
See:
https://www.zurich.ibm.com/st/electr...rconnects.html
And here is where the trouble comes in. IBM had practiced solder ball techniques since the 1960s and found it to be robust and reliable. But when lead-free solder was introduced, the reliance on tin-lead's ductility (ease of deforming) became apparent. As integrated circuits became more dense, heat became an issue. A printed circuit card does not have the same thermal coefficient of expansion as an IC substrate. The amount of power dissipated in an IC became limited by the temperature the complete assembly could withstand.
In an interesting engineering blunder, in the first version of the XBox gaming computer, the graphics chip had been designed by Microsoft engineers. (They had reportedly had a bid from Nvidia, an experienced graphics chip design firm to do the design for $5 million, but the in-house engineers had convinced their management they could do the work for $1 million.) The design performed as expected, but the designers had failed to do heat calculations and reducing the power used by non-critical circuit paths. (The faster any path must be, the more power it takes.) The chip ran at a temperature way hotter than the packaging could withstand, the chip and substrate expanded and contracted at different rates, and eventually the lead-free solder balls broke. When this happened, the startup program detected an error and signaled "General Hardware Failure." This was indicating three LEDs surrounding the power button individually, in sequence. This ultimately became known as the Red Ring of Death.
Source: ttps://en.wikipedia.org/wiki/Xbox_360_technical_problems#:~:text=Three%20flashi ng%20red%20lights%20around,Blue%20Screen%20of%20De ath%20error.
I remember reading "Yoshida, Junko (June 9, 2008). "The truth about last year's Xbox 360 recall". EE Times.", referenced
here as footnote 30.
This application of lead-free solder cost Microsoft over $1 billion from an attempt to save $4 million.
A newer problem
I'm not sure if this is a newer problem or one that we are slower to recognize. Lead-free solder does not "wet" the metals you are soldering as well as tin-lead solder does. Those of us who have "sweated" copper pipe before and after the cutover have surely recognized this. It simply doesn't alloy as well with the pipe and fittings. And those who work in electronics have surely seen this, too.
One of the things that was done to try to improve this was to use stronger, more active fluxes. Prior to the introduction of lead-free solder, a very mild resin (customarily spelled "rosin") was used on electronics. One of the first things novices learned is that corrosive acid-core solder was NEVER used on electronics, just on thick items like copper pipe.
As Chaps2018 mentions above, we are seeing corrosive fluxes used to hide the problems with lead-free solder. It simply eats right through fine, stranded wire. He saw it on a fan.
You know those Harbor Freight flashlights they used to give away: blue with two parallel sides and two semi-circular ends? (The name for this shape is "stadium".) I must have a dozen of them here. I used each one until it got intermittent and I had to bang it to make it work. I've taken a few apart. each has two hand-soldered wires, one from battery+ to switch and one from switch to printed circuit card. All four ends were eaten away. When I first looked at this I thought "Gosh, they couldn't have used acid-core solder for this!" As I was reading Chaps' post, I realized this was simply a flux made for lead-free solder. Score another point for the EU Commission and RoHS!
{/RANT}
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