I am not an expert, just an interested witness to this 'RoHS solution' party. Tin whiskers are not a recent phenomena, they were first noticed back in the 1940's.
If you are really interested, you need to read this NASA report. It is quite an article about how whiskers can materialize within days or weeks. They can start, stop and then resume for no known reason.
That is the problem - there is no means of determining when or where they will occur as the cause is unknown - just be assured they will develop. Thankfully most do not cause a major issue and infrequently significant damage. Voltage does impact the presence (growth) but NASA claims they develop in vacuums, which eliminates most arguments for what we can do to prevent them.
The most serious implications are that they will penetrate conformal coatings - the only assured method to prevent it appears to be that adding Pb inhibits the growth, again the reason is unknown.
Keith, it is my understanding that tin whiskers form long after the product is completed, shipped and in use. Typically they form when the solder is under stress, which makes the problem most common in military and aerospace applications. At least that's when I've seen in NASA reports.
350 F should remove tin whiskers as the melting point of tin particles is 177 C or 350 F. Tin Whiskers range in size from 6 nm to 10 um - well within the specification of a tin particle. Besides, 'normal handling' of a PCB will break the whiskers as most individuals do not handle PCBs properly outside of the industry and they cannot 'see' the root cause.
I've had problems with an HP printer I purchased about 4 years ago. I finally gave up on it. My guess is the quality problems coincide with outsourced manufacturing.
I have been fighting a problem with Mitsubishi PLCs model FX2n. They were built about the time RoHS was first being implemented. I have about 300 of them on machines around the country, and so far 5 of them have lost their minds, each in a different way. One started making addition error. Another kept changing the value of one of the customer input data. Another kept changing several of the values of battery-backed parameters. Etc. Mitsubishi is no help, all they say it that it can't be doing it or it must be my programming of it. Of course they can't explain why I have 295 out there with the same programming that work fine, or why these worked fine for years.
So I am very eager to try baking one of these, and see if that fixes it. However, I am not sure what parts can withstand the heat of baking. Does anyone have a list of things that can't be baked?
Most lead free solder used in electronic production melts around 220C (428F) and reflow temperatures are slightly higher. I have to doubt that a 350F oven fixed a lead free solder problem.
Most likely the baking helped with either a moisture/conductivity problem, or with a thermal intermittent. Two problems in PCB manufacturing came along at almost the same time -- the switch to brittle, lead-free solder, and the switch to water-soluble flux. I've seen problems caused by both issues that could be "fixed" by baking.
If you have a cracked solder joint, the only permanent fix will be to find it and re-solder it with good solder. Typically, it's heavy components with large tabs that have the soldering problems, both because the thermal mass of the heavy part tends to result in a cold solder joint under the best of circumstances, and the weight of it exacerbates any vibration or thermal expansion problems, which can crack brittle solder. An engine control relay module in ~1990 Honda Civics was notorious for that.
If conductivity is the issue, if the device is kept in a warm dry environment henceforth, it may be fine. If not, the best solution is to scrub the board with warm, soapy water and a soft brush, blow it dry with clean air, bake it to drive out remaining moisture, and if operation over a wide range of temperature or humidity is expected, spray both sides with two thin coats of a conformal coating. Ordinary clear acrylic enamel can be used, but I prefer the silicone coating for its flexibility.
In 1987 I started a small business and purchased a HP Laserjet Series II Printer. I used it heavily at first and it worked well. A few years later it was out of warranty but I got a local fixit place to repair something on the motherboard that had failed. Later I replaced a damaged platen that cures the toner. The first repair was $100, the second $26. The business closed but I kept the printer. I am still using it now, having gone through 8-10 print cartridges (10,000 pages per cartridge). The majority of my printing is documents and it still puts out a clean page. A little slow, but I am not in a hurry. It is now 24 years old and the current cartridge cost $90, but it is least the last 4 years and still doing well.
Planned obsolence - I think that is too much credit to our fellow marketers.
As much as RoHS has become a necessary evil, it remains an evil. Tin Whiskers are going to haunt us until someone determines its cause and a means to end it. NASA's link: http://nepp.nasa.gov/whisker/reference/tech_papers/2011-kostic-Pb-free.pdf desribes how 'bad' product can suddenly be good as arching removes the 'short' caused by tin whiskers. I suspect there are many issues occuring that are blamed on people that are caused by lead-free electronics - Check out NASA's report on the Toyota sudden acceleration cause.
So the next time you have a 'bad' electronic device, take it apart and hit the electronics with some compressed air - you will probably save yourself some serious dough. Just remember - the problem will come back....
1) Have a OKIDATA ML 391 wide-carriage printer connected to a DELL 486/33 PC that I still use for one program. PC & Printer are over 20 years old & still working!
2) Also have a H-P IIIP laser printer which I alternately connect to the DELL 486 or to the DELL TOWER w/ WINDOWS XP PRO. Still works, after 20 years, BUT I did replace the laser motor board assembly about 6 years ago. The kit came w/ a new board assembly AND a VCR tape w/ EXACT tear-down, remove, install, re-build instructions. Just bought a new (NOT replenished!) toner cartridge from an outfit in California. Was about $40.
3) Did considerable p.c. board design work several years ago using EAGLE software. So, I needed a color printer for checking the layouts. Bought an EPSON printer from OFFICE DEPOT. Was less than $100. Used it, but had some install problems (drivers, etc.) Needed to go to EPSON website for updated drivers. Worked OK after that. After only about 18 months of use I didn't need it anymore, so it sat next to the PC. When I tried it again, the ink wouldn't flow. Tried their built-in Diagnostics, and Printhead cleaning routine several times. The ink was too caked. Then I remembered that I had a 2 year warranty from OFFICE DEPOT. With only one month to expiration, I brought it back to the same store, filled in the paperwork, and received ALL my money back, including the sales tax. That was the BEST part of owning an EPSON printer.
I am also an avid amateur photographer, who shoots digital AND film. I hesitate to purchase a decent photo quality printer for several reasons, mostly I'm afraid of spending a sizable amount on the printer (CANON has some real doozies!!), only to see the printheads get permanently plugged. For images which I want to publish, I do the same as RATSKY suggested..... downloading them to a drive or to the photo shop for printing on their high-end machines.
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