Just to add my C$0.02 worth of opinion: lead-free solder is unlike your lead-loaded solder (63/37 or 60/40).
Aside from the much higher melting temperature (over 60 degrees Celsius, which brings it closer to 240 C), it behaves differently and doesn't wet (i.e., creates the nice solder joint) or shines as lead/tin. It normally contains Silver, Bismuth, Antimony and/or Copper among other such metals. Each lead-free assembly is usually marked with Pb-free in the silkscreen, or crossed-out Pb in a circle, or sometimes RoHS compliant. In reality, lead is allowed to be in the assembly, up to 0.1% by weight. This started as a noble idea by the EU, quickly copied by California and some other countries (China, Japan, south Korea come to mind), to address the dumping of consumer electronics with regular trash and the potential to contaminate ground water. The geniuses didn't realize that the cure is possibly worse then the problem: lead-free (Pb-free) is much more brittle thus will bring more failing electronic assemblies to the dump, which will increase the amount of garbage. Tin whiskers, as well as other maladies, are also an issue, so be gentle with your electronics. On Sat, Mar 27, 2010 at 00:10, Jim Scott <jesco...@gmail.com> wrote: > > > On Thu, Mar 25, 2010 at 1:27 AM, Clark Martin <cm...@sonic.net> wrote: > >> On 3/24/10 2:20 PM, Bruce Johnson wrote: >> >>> >>> On Mar 24, 2010, at 12:31 PM, Jim Scott wrote: >>> >>> The most difficult part -- aside from my steep soldering learning >>>> curve ascent -- was removing the original capacitors. Apple used >>>> lead-free solder in those iMacs, and I literally burned up several >>>> solder guns of increasingly higher heat capacity before I got one that >>>> could melt the original solder enough to free the bad caps. >>>> >>> >>> You need to get a decent temp regulated soldering iron, Harbor frieght >>> used to have one for about $40, a quick googling finds them at >>> $30-$120-ish. >>> >> >> One of the mistakes people commonly make in soldering is using too small a >> soldering iron. What happens with a too small iron is the iron heats things >> up but the heat is conducted away to fast. The heat spreads out and damages >> things but it either doesn't reach the melting point of solder or it takes >> too long. >> >> For this sort of job I would probably use a 25W iron or perhaps a 40W, >> depending on the size of the caps. >> >> Of course the other big mistake is to use too much heat. > > > I had successfully soldered and desoldered a number of components on a lot > of boards before I took on my first iMac G5 project. But Jim Warholic < > http://jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php> cautioned > that a super-hot iron with quick heat recovery was necessary to melt the > lead-free solder used on the iMac G5 logic board. He recommended at least a > 60 watt iron. He was right. My 45-watt Radio Shack iron didn't do the job. > Then I moved up to a 75 watt Weller. No go. Then to a 100/140 watt Sears > gun. No go. Then finally I achieved success with a 130 watt Weller with a > "turbo" trigger that could deliver short bursts of 930 degree F. heat. Even > then I had to wait between capacitors for the iron to recover sufficient > heat to melt the next two capacitors legs free. Removing original caps from > iMac G5 boards is very hard to do, and Warholic was spot on with his warning > and his advice. There's something about those boards and the solder used > that's "different." Try desoldering a cap on one and you'll understand. > > -- You received this message because you are a member of the iMac Group, a group for those using Apple iMacs and eMacs. The list FAQ is at http://lowendmac.com/imac/list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to imaclist@googlegroups.com To leave this group, send email to imaclist+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/imaclist To unsubscribe from this group, send email to imaclist+unsubscribegooglegroups.com or reply to this email with the words "REMOVE ME" as the subject.
