Out-of-tolerance zero ohm resistors - Page 6

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: Out-of-tolerance zero ohm resistors
On Mon, 1 Jun 2015 14:28:53 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Quoted text here. Click to load it

That's true for thick gold. A few microinches of gold will immediately
dissolve into the solder and become only a trace component.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

We've slightly trimmed the long signature. Click to see the full one.
Re: Out-of-tolerance zero ohm resistors
On Mon, 1 Jun 2015 14:28:53 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:

Quoted text here. Click to load it


  Maybe that is why "too much" is never used on PCB pads.

  One has to 'wet', then release or wick, then re-wet", then repeat with
gold cup mil std solder pins...   NOT circuit pads.  Not much else at
all, in fact.

  There is no embrittlement on PCB assemblies.  Doh!  Edge connected or
through-hole SMA connectors or other gold plated "connectors"  and test
pins MAYBE, but not likely.  Mil std connector pins using solder cups
not crimps....  definitely, abated by using the above described
procedure.  PCB pads...   NOT!

  You read a lot, but understand little, much less KNOW.  Or you would
know the difference between one micron and several.  And your little
dogs too.

Re: Out-of-tolerance zero ohm resistors
On Tuesday, 2 June 2015 03:21:31 UTC+1, DecadentLinuxUserNumeroUno  wrote:

Quoted text here. Click to load it
Oh dear.
What?




Re: Out-of-tolerance zero ohm resistors
On Tue, 2 Jun 2015 01:58:55 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:

Quoted text here. Click to load it
  Gee...  junior willackers.

 ONE MICRON of gold is NOT going to cause intermetallics or
embrittlement..  Dig?

  A gold plated mil cup which is not properly evacuated first WILL cause
it in the wire that gets soldered into it.  That is why there is an
evacuation procedure. That is also why the military gets an RoHS
exemption. GET A CLUE.


Re: Out-of-tolerance zero ohm resistors
On Tuesday, 2 June 2015 13:23:34 UTC+1, DecadentLinuxUserNumeroUno  wrote:
  
Quoted text here. Click to load it

That obviously depends on the solder thickness.

However, you carefully missed the point.  You originally claimed that:
"...if you want to sell in Europe, you have to use lead-free, and that
means gold on nickel."

This is simply not true.  Many other board finishes are suitable for
lead-free.  I gave an example.
  
Quoted text here. Click to load it

Both tin-lead and lead-free solders can be affected by excessive
dissolved gold, so that can't be the reason for the military having
their RoHS exemption.  Maybe other factors like tin whiskers are
involved.

John

Re: Out-of-tolerance zero ohm resistors
On Tue, 2 Jun 2015 23:05:46 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:

Quoted text here. Click to load it

  It is not the sole reason, but it is one of the reasons.

Re: Out-of-tolerance zero ohm resistors
On 06/03/2015 02:05 AM, snipped-for-privacy@gmail.com wrote:
Quoted text here. Click to load it

Lots of cycling over extreme ranges of temperature and humidity is a  
good way of growing whiskers.  Lead-free solder is also mechanically  
harder than Sn63Pb, which makes the fatigue problems in pad metal and  
board traces worse.

Also there's some residual vague sense of proportion someplace--the lead  
prohibition was originally intended to protect people involved in  
recycling electronics, iirc, and maybe (just perhaps, you know?) people  
being shot at are in a bit more danger than they are.

Cheers

Phil Hobbs

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
We've slightly trimmed the long signature. Click to see the full one.
Re: Out-of-tolerance zero ohm resistors

Quoted text here. Click to load it


  Gold does NOT oxidize.

Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 23:42:57 -0400, DecadentLinuxUserNumeroUno

Quoted text here. Click to load it

Good Lord, AlwaysWrong.  Learn to read!

Re: Out-of-tolerance zero ohm resistors

Quoted text here. Click to load it

All mil PCBs these days are Gold plated traces and pads. and vias.

  Not rare at all.

Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 23:21:58 -0400, DecadentLinuxUserNumeroUno

Quoted text here. Click to load it

You're always wrong, AlwaysWrong.


Re: Out-of-tolerance zero ohm resistors

Quoted text here. Click to load it


  Nope.  A rivulet was when the solder mask was loose enough that the
traces filled up with solder appearing like tiny rivers under the mask.
It would have been simple had you simply gone and looked up the term.
Typical of old power supplies and cheaper PCB assemblies.  HASL and
tighter mask layers fixed it in most cases.  Yer brain must be rivetted.
Maybe that is an IBM fellow thing.  Hehehe.

Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 23:25:15 -0400, DecadentLinuxUserNumeroUno

Quoted text here. Click to load it

We had another name for them. SOlder would bunch up on traces and make
bulges in the solder mask, sometimes crack it.

The fix was SMOBC, so that there was no solder on masked traces.


--  

John Larkin         Highland Technology, Inc
picosecond timing   laser drivers and controllers

We've slightly trimmed the long signature. Click to see the full one.
Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 23:25:15 -0400, DecadentLinuxUserNumeroUno

Quoted text here. Click to load it

No, I was not an IBM Fellow.  Just a design engineer.  Idiot!  

You're still AlwaysWrong.


Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 13:50:05 -0400, DecadentLinuxUserNumeroUno

Quoted text here. Click to load it

We only do gold-over-nickel these days. ENIG.

If it really matters, our fab note will say

  START WITH 2 OZ COPPER

so they don't short-cut the plating. And if it really matters, I'll
include a test trace that I can ohm out. And TDR.

Most boards' copper seem to come out a little on the thin side these
days. We seldom get actual 1 Oz.


--  

John Larkin         Highland Technology, Inc
picosecond timing   laser drivers and controllers

We've slightly trimmed the long signature. Click to see the full one.
Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 14:42:24 -0700, John Larkin

Quoted text here. Click to load it

Good idea.  At the PPOE, we were failing ICT on one land with one of
the products.  Turns out that purchasing went to a new "cheaper"
supplier in India.  One of the nets went over the 3-ohm open-limit
(should never have been more than ~.1 ohm).  They blamed it on "some
necking" at corners.  Yeah, right.
  
Quoted text here. Click to load it

True, particularly if you're plating up from .5oz (typical).  Our
quality group is all over the suppliers where it matters (==where
specified).

Re: Out-of-tolerance zero ohm resistors
On 29/05/2015 16:13, snipped-for-privacy@yahoo.com wrote:

<snipped>

Quoted text here. Click to load it

Sound like the substitute parts are skimping on the Siemens, using only  
80 instead of 400.  It's certainly sharp practise, that way they can  
make five times as many parts from one bag of Siemens, plus the counting  
is quicker.

Cheers
--  
Syd

Re: Out-of-tolerance zero ohm resistors
Quoted text here. Click to load it

Quoted text here. Click to load it
  
Quoted text here. Click to load it

Yeah, they took lhe line of least resistance. No, wait....

Cheers

Phil Hobbs

Re: Out-of-tolerance zero ohm resistors
On Sunday, May 31, 2015 at 7:59:52 AM UTC-4, Phil Hobbs wrote:
Quoted text here. Click to load it
  

  
Quoted text here. Click to load it
  
Quoted text here. Click to load it

Resistance is fuse-ile.

(Better ablate than never?)

Cheers,
James Arthur

Re: Out-of-tolerance zero ohm resistors
On Sun, 31 May 2015 04:59:49 -0700 (PDT), Phil Hobbs

Quoted text here. Click to load it

Quoted text here. Click to load it

  *film* of least resistance?

Site Timeline