60/40 vs. 63/37 Solder
in [Basics]
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From: John Fields on 18 Jul 2010 17:14 On Sun, 18 Jul 2010 11:44:51 -0700, "William Sommerwerck" <grizzledgeezer(a)comcast.net> wrote: >>> Correct. The original writer was probably confused by the >>> fact that the materials ceramic ICs are made of can contain >>> radioactive materials that can cause errors. > >> No, the alphas from lead are a real problem. Ten years ago, there were >> folks going round to churches with lead roofs, offering them a new lead >> roof in exchange for their old--and now low-alpha--lead ones. > >But where is the lead /within/ ICs? (The wires are bonded, not soldered.) >Alpha particles have poor penetrating power. --- In the lead frame? ;)
From: Phil Hobbs on 18 Jul 2010 19:47 William Sommerwerck wrote: >>> Correct. The original writer was probably confused by the >>> fact that the materials ceramic ICs are made of can contain >>> radioactive materials that can cause errors. > >> No, the alphas from lead are a real problem. Ten years ago, there were >> folks going round to churches with lead roofs, offering them a new lead >> roof in exchange for their old--and now low-alpha--lead ones. > > But where is the lead /within/ ICs? (The wires are bonded, not soldered.) > Alpha particles have poor penetrating power. > > Only a problem with flip-chip (C4) bonding. At one point I worked in the packaging research group at IBM Yorktown lab (no, I'm not a packaging guy--it's a long story). Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: krw on 18 Jul 2010 20:13 On Sun, 18 Jul 2010 19:47:15 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >William Sommerwerck wrote: >>>> Correct. The original writer was probably confused by the >>>> fact that the materials ceramic ICs are made of can contain >>>> radioactive materials that can cause errors. >> >>> No, the alphas from lead are a real problem. Ten years ago, there were >>> folks going round to churches with lead roofs, offering them a new lead >>> roof in exchange for their old--and now low-alpha--lead ones. >> >> But where is the lead /within/ ICs? (The wires are bonded, not soldered.) >> Alpha particles have poor penetrating power. >> >> > >Only a problem with flip-chip (C4) bonding. At one point I worked in >the packaging research group at IBM Yorktown lab (no, I'm not a >packaging guy--it's a long story). The C4 balls were lead-indium, IIRC.
From: Phil Hobbs on 18 Jul 2010 20:32 krw(a)att.bizzzzzzzzzzzz wrote: > On Sun, 18 Jul 2010 19:47:15 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> William Sommerwerck wrote: >>>>> Correct. The original writer was probably confused by the >>>>> fact that the materials ceramic ICs are made of can contain >>>>> radioactive materials that can cause errors. >>>> No, the alphas from lead are a real problem. Ten years ago, there were >>>> folks going round to churches with lead roofs, offering them a new lead >>>> roof in exchange for their old--and now low-alpha--lead ones. >>> But where is the lead /within/ ICs? (The wires are bonded, not soldered.) >>> Alpha particles have poor penetrating power. >>> >>> >> Only a problem with flip-chip (C4) bonding. At one point I worked in >> the packaging research group at IBM Yorktown lab (no, I'm not a >> packaging guy--it's a long story). > > The C4 balls were lead-indium, IIRC. Lead-tin eutectic in my era (1987-2008), followed by gold-tin currently, IIRC. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: krw on 18 Jul 2010 20:43
On Sun, 18 Jul 2010 20:32:22 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >krw(a)att.bizzzzzzzzzzzz wrote: >> On Sun, 18 Jul 2010 19:47:15 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> William Sommerwerck wrote: >>>>>> Correct. The original writer was probably confused by the >>>>>> fact that the materials ceramic ICs are made of can contain >>>>>> radioactive materials that can cause errors. >>>>> No, the alphas from lead are a real problem. Ten years ago, there were >>>>> folks going round to churches with lead roofs, offering them a new lead >>>>> roof in exchange for their old--and now low-alpha--lead ones. >>>> But where is the lead /within/ ICs? (The wires are bonded, not soldered.) >>>> Alpha particles have poor penetrating power. >>>> >>>> >>> Only a problem with flip-chip (C4) bonding. At one point I worked in >>> the packaging research group at IBM Yorktown lab (no, I'm not a >>> packaging guy--it's a long story). >> >> The C4 balls were lead-indium, IIRC. > > >Lead-tin eutectic in my era (1987-2008), followed by gold-tin currently, >IIRC. The last time I dealt with any of this was in the mid '70s. Before TCMs, even (LEMs). I'm pretty sure they were lead-indium, but there may have been tin in there too. There was also an issue of polonium contamination causing uncorrectable L1 errors, but that's a completely different issue. |