It's (past) time for us to get some more solder paste. There's a paste that seems to have twice the rated shelf life of those available on DigiKey:
Has anyone tested this stuff to see how well or badly it induces surface leakage on circuit boards? Our old paste did fairly well without cleaning the boards. {They also sell a water-clean form but generally these are horrible for leakage}
TIA!
I use Kester R276 paste (p/n 70160705200). No leakage problems. Not easy to get from mainstream distributors any more, but Adafruit has it.
Cheers
Phil
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
one too many zero's in the pn.
George H.
Quite so--my error. But Digikey shows zero stock.
Cheers
Phil Hobbs
Thanks. Kester doesn't seem to have much information on its chemistry (surprise!). Kester shows it being available a variety of sources, but many of those have '0 stock' ;
If you follow the octopart link it says Kimco has stock. There are also data sheet links.. shlef life is 6 months. (kept in a frig.)
GH
Thanks... seems like standard paste shelf life.
All of the reputable P&P shops hate so-called "no clean" since that crap makes more of an undesirable mess than the oldie but goodie acid core (just joking about acid core). "No clean" is a lie, needs more cleaning than anything else, and apparently the same level as if one was using acid core.
Octopart.com sucks...used "silver solder" as searchterm and got a gazzillion "american torch tips"...nonsequiter. Then tried checking the "lead free" box; a lot less NOT RELATED junk.
and
"No clean" with SnPb actually means good old rosin flux, with all the same properties we're used to since forever.
Cheers
Phil Hobbs
follow the link on octopart, it's explained.
some background:
-- This email has not been checked by half-arsed antivirus software
That's what I'm hoping for. Don't need "pretty", just reliable connections without leakage in high impedance applications.
I beg to differ. "No clean" flux is decidedly different WRT rosin flux, RA, RMA, etc.
Quote from
Soldering requires flux to dissolve oxides and to promote wetting. Rosin (made from tree sap) is one flux material that has long been popular, and comes in various strengths- RMA (Rosin Mildly Activated) or RA (Rosin Activated). Kester says you can leave the flux on the board under fairly benign conditions and experience bears that out (it only becomes active = corrosive) at elevated temperatures, however most manufacturers will clean the board for cosmetic reasons and to allow inspection. Cleaning often involves the use of petroleum solvents- for example by vapor degreasing or just scrubbing.
Aqueous clean fluxes have been developed that can be cleaned without solvents- using just hot water and detergent.
No clean fluxes allegedly don't need to be cleaned and can be left on the board, however many of us have had problems with no-clean processes having relatively conductive residue. The residue is ironically extremely hard to remove, much more difficult than the two above-mentioned processes, more like 'can't clean'. Think twice about this kind of flux if you're thinking of sensitive analog boards that have high impedances. Even circuits you may not think of as being analog such as RTCC chips with an external crystal may be affected.
Safest for sensitive boards is rosin flux followed by a thorough cleaning process.
A, etc.
According to the Kester guy, R276 is rosin flux, which is what "no-clean" m eans _with_SnPb_. Last time I checked, there were exactly zero types of pas te advertised as using rosin flux. The buzzwords are different.
Cheers
Phil Hobbs
Well you have to use a tool the right way. If you know a part number octopart is great for checking stock/prices at various distributors. I've never used it find a part. (Digikey is my fav for that.. though not perfect.)
George H.
RMA, etc.
means _with_SnPb_. Last time I checked, there were exactly zero types of p aste advertised as using rosin flux. The buzzwords are different.
I've had issues with this "non-wash" flux.
George H.
The datasheet says "water soluble" right on it. I've done picoamp TIAs with R276, no worries.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Huh? You mean the data sheet in the Newark link? That seems to be for all of Kester's solder products. There is nothing very specific in it about the "245" flux, that I can find. (it's listed on page 10) I was just saying that not all "no-clean" fluxes with Sn/Pb, Rosin activated are going to be benign at high impedance. YMMV
George H.
Missed that, you're right. It says that 245 is rosin. What sort of problems did you have with it?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Oh snap, I knew you'd ask that. To be honest I've forgotten. It could have been leakage, or it could have been just because the pcb's looked ugly. I've got a few rolls on my shelf, I'll check.
OK a quick test shows no leakage at the 100 meg ohm level. slightly bigger guns, no leakage at the ~10 Gig level... (Signals are looking ugly... ~60Hz, maybe from the power supply.)
OK maybe this flux isn't as bad as I thought. George "44" Herold
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