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'[EE]: Soldering - wet sponge'
2000\10\16@012430 by staff

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Arthur Brown wrote:
>
> Hi Lindsay,

> One of the most important things is the Tip must be kept clean use a wet
> sponge and if your tip is copper replace with an iron plated one, this will
> last longer. use the tin of tip cleaner sparingly as it's very corrosive.
>
> Regards Art


Oh, no! I can see this might start a big flame war but here goes.
We stopped using "wet sponge" in the workshops here about 10 years
back, it's just not the best method. Cooling the tip from 350 degrees
down to 20 degrees over and over causes metal fatigue and porosity
of the tip, and a porous tip (ie, rough, lots of tiny holes etc)
is no good to solder with.

I have had regular fights with my apprentices who have just finished
soldering/hand tools (yr1 subject) over this. They get taught the "wet
sponge" stuff by the teacher so it must be right! ;o)

The system we use in the two workshops here is the "solder blob"
method, basically it replaces the wet sponge with a big solder
blob. When the tip gets dirty, you apply fresh solder, give the
core flux a second to do it's job and then wipe it on the solder
blob. All the crud gets wiped onto the blob, which grows in size.
The tip gets clean and polished.

This has a lot of advantages. Doesn't make steam, doesn't cause
tempering damage to the tip from rapid cooling, no constant wetting
of the sponge is needed, and the best benefit is that the tip is
slowly polished by the rubbing against metal (solder blob), and
after a few weeks like this the tips get really good, because they
are non-porous and polished all the crud wipes straight off and
wetting is excellent. We get 3 times the life from tips now compared
to the old days. It's quicker, little/no re-heat time needed, as
the tip doesn't cool much. There is also always some residue flux
left in your big solder blob, so rubbing the tip on this blob causes
great cleaning.

I cringe when I have to use another iron that sees "wet sponge"
usage. It really is a step backward. I also hate using new tips,
knowing it will be a couple of weeks before it gets polished enough
to give good performance like the old ones did.

For the record, I like the Weller magnetic type irons, good steel
jacket tips. We only have to replace them when they get arc damage
from soldering charged caps (we've all done it!) as with the
solder blob method they don't wear out.
-Roman

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2000\10\16@061615 by mike

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On Mon, 16 Oct 2000 16:21:47 +1000, you wrote:

>Arthur Brown wrote:
>>
>> Hi Lindsay,
>
>> One of the most important things is the Tip must be kept clean use a wet
>> sponge and if your tip is copper replace with an iron plated one, this will
>> last longer. use the tin of tip cleaner sparingly as it's very corrosive.
>>
>> Regards Art
>
>
>Oh, no! I can see this might start a big flame war but here goes.
>We stopped using "wet sponge" in the workshops here about 10 years
>back, it's just not the best method. Cooling the tip from 350 degrees
>down to 20 degrees over and over causes metal fatigue and porosity
>of the tip, and a porous tip (ie, rough, lots of tiny holes etc)
>is no good to solder with.
..which is why you don't use a _wet_ sponge but a _moist one_ to avoid
cooling the bit too much.  The only pain is that it dries out fairly
quickly.

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2000\10\16@065848 by Arthur Brown

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Hi all,

When I said Wet sponge of cause I meant damp sponge and the iron is cleaned
on the way back to the irons test, not on the way from the rest to joint
being done.
I did not to give a very detailed account of every action in the process of
keeping the tip of the iron clean. But the original poster did say he had an
iron was tip was so contaminated that the only way to clean it would be to
take a file to it.

The point I was making was it's very important to keep the irons tip clean.

You could use loads of tip cleaner but that is not the best way as it is
costly both money wise and in replacing tips.
The job in hand is also contaminated by the strong cleaning compond used.
In the past I have seen people use tip cleaner for every joint they make.

The tip I have in my Weller 1301 is Only 8 years old, do you think it may
win an award for long service.
mind you it's now only used 2 days a week now as it's on my rework bench.
but it's on for 48-46 hours.

now saying that what's the odds it now fails at the next switch on....

I have done a lot of Ministry of Defence rework for a well known British
company
and you have to follow their rules. for example ESD, Work Shop practice,
down to what is allowed in the shop and what's not.
Soldering standards include  things like if you replace a resistor you trim
the lead to length before soldering, I have seen work rejected because
someone cleared the pads
inserted resistor soldered the resistor in circuit then cut off surplus lead
length. so I think every job as to be done to the standards of the employer.

Regards Art

{Original Message removed}

2000\10\16@172932 by Tony Nixon

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Arthur Brown wrote:

> Soldering standards include  things like if you replace a resistor you trim
> the lead to length before soldering, I have seen work rejected because
> someone cleared the pads
> inserted resistor soldered the resistor in circuit then cut off surplus lead
> length.

I always leave the leads intact while soldering because they provide an
extra measure of heat transfer away from the component.

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2000\10\16@175052 by ArthurBrown
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Hi Tony.

The reasons for the work being rejected was that

1. cutting the lead put the joint under stress.?  <unlikely>
2. the end of lead was exposed something to do with oxidation. <again
unlikely>

I know that sounds daft but this was military hardware and in this piece of
kit all the via's had to be filled with Solder, again for what reason?.

Regards Art

Ps.  Tony How is your Programmer Project going? < have you pasted the Seven
Code runs yet? <BBG>

{Original Message removed}

2000\10\17@054556 by mike

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On Mon, 16 Oct 2000 22:46:16 +0100, you wrote:

>Hi Tony.
>
>The reasons for the work being rejected was that
>
>1. cutting the lead put the joint under stress.?  <unlikely>
If it's cut too close to the solder blob (i.e. cuts part of the joint)
it could potentially put stress on the pad.
>2. the end of lead was exposed something to do with oxidation. <again
>unlikely>
>
>I know that sounds daft but this was military hardware and in this piece of
>kit all the via's had to be filled with Solder, again for what reason?.
Probably to reduce the risk of the via detatching from the pad under
extreme stress/vibration conditions.
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2000\10\17@085425 by Olin Lathrop

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> Soldering standards include  things like if you replace a resistor you
trim
> the lead to length before soldering, I have seen work rejected because
> someone cleared the pads
> inserted resistor soldered the resistor in circuit then cut off surplus
lead
> length.

I'm curious.  What is the advantage to trimming the lead before soldering?
I would have thought the other way around to be more reliable.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olinspamKILLspamcognivis.com, http://www.cognivis.com

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2000\10\17@093145 by Don Hyde

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It's a very fine point.

If you trim the leads before soldering, then the trimmed end of the lead
will get coated with solder.  Since this prevents the exposure of a junction
of dissimilar metals to the atmosphere, it is less susceptible to corrosion.

> {Original Message removed}

2000\10\17@094733 by Andy Howard

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> From: "ArthurBrown" <EraseMEartbspam_OUTspamTakeThisOuTCABLEINET.CO.UK>

> I know that sounds daft but this was military hardware and in this piece
> of kit all the via's had to be filled with Solder, again for what reason?.


Maybe it was to restore some of the mechanical strength of the boards lost
by the drilling?

If so they're wasting their time. As anyone who's ever tried to tear a stamp
from a sheet or a cheque from a stub can attest, the perforations are
invariably the strongest part...





.

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2000\10\17@110311 by Spehro Pefhany

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At 08:21 AM 10/17/00 -0400, you wrote:

>I'm curious.  What is the advantage to trimming the lead before soldering?
>I would have thought the other way around to be more reliable.

It avoids the possiblity of fracturing the solder joint or lifting a
pad when cutting the joint. The latter can be a particularly common failure
mode on single sided boards with heavy-leaded parts in sloppy holes (typical
consumer electronics construction for easy assembly).

Best regards,
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2000\10\17@112254 by staff

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Olin Lathrop wrote:
>
> > Soldering standards include  things like if you replace a resistor you
> trim
> > the lead to length before soldering, I have seen work rejected because
> > someone cleared the pads
> > inserted resistor soldered the resistor in circuit then cut off surplus
> lead
> > length.
>
> I'm curious.  What is the advantage to trimming the lead before soldering?
> I would have thought the other way around to be more reliable.


I can believe this! A lot of the problems with bad joints we get in
TVs are because the exposed tip of the steel leg started to corrode,
then this travelled down the outer surface around the leg and eventually
dry jointed. Dissimilar metals and oxygen and stuff. When re-soldering
these bad joints I scruff the top surface of the pin as well as the
sides, so the solder then forms a full seal around it.

I was very intrigued by the military soldering info, I think it
would be very schmick to cut the leads just clear of the board,
then solder them to completely cover the lead and protect it from
the environment. Sounds like a bit more work, and may need something
to hold the component while soldering so it doesn't fall out.

If we didn't already encapsulate our product and use very cool running
parts I would consider this. Classy move, especially where the parts
run warm or are exposed to the air. Also filling the vias is a classy
move, thinking about doing that one!
-Roman

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2000\10\17@131145 by Andy Howard

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> From: "Olin Lathrop" <spamBeGoneolin_piclistspamBeGonespamCOGNIVIS.COM>


> > Soldering standards include  things like if you replace a resistor you
> > trim the lead to length before soldering, I have seen work rejected
> > because someone cleared the pads inserted resistor soldered the resistor
> > in circuit then cut off surplus lead length.

> I'm curious.  What is the advantage to trimming the lead before soldering?
> I would have thought the other way around to be more reliable.

According to one mil-supplier I did some work for recently it's because of
the shock-loading of the finished joint when the lead is cropped. Seems a
little excessive to me, but then I suppose that at the prices the military
pay, they could have their stuff made exclusively by left-handed unicyclists
if they
ask...



.

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2000\10\17@132326 by M. Adam Davis

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And colleges would start including classes to teach left-handedness and
unicycling in the core cirriculum of the engineering degrees...

Andy Howard wrote:
> I suppose that at the prices the military
> pay, they could have their stuff made exclusively by left-handed unicyclists
> if they ask...

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2000\10\17@140416 by Bruce Cannon

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I got the part about precutting leads, but why fill the vias again?

Bruce Cannon
Style Management Systems
http://siliconcrucible.com
(510) 787-6870
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Remember: electronics is changing your world...for good!

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2000\10\17@152458 by dre Domingos F. Souza

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>I got the part about precutting leads, but why fill the vias again?

       Corrosion. Sometimes a via can get corroded in a point it inserts a significant resistance on the circuit, or even interrupt a circuit. When it happens, as you say, it's a "pain in the ass" to fix. I've seen lots of cases of things like this happening. And it's always hard to troubleshoot. you only find the fault when you have nothing else to see.


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2000\10\17@161146 by Spehro Pefhany

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At 10:59 AM 10/17/00 -0700, you wrote:
>I got the part about precutting leads, but why fill the vias again?

It's not all that uncommon for there to be a micro-crack at the
interface between the plated hole barrel and the traces. Easy to
see when you section the PCB and look at it through a microscope,
difficult to inspect non-destructively.

Putting solder in the hole makes the vias more reliable because it
flows from top to bottom, not relying solely on the integrity of
the plating.

This used to be a very big problem with boards, it is much less
these days, but if you are paying $10,000 per pound to loft
something into space, putting it under the ocean or if someone's
life might depend on it, it seems like cheap insurance.

Best regards,

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2000\10\18@053757 by staff

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Bruce Cannon wrote:
>
> I got the part about precutting leads, but why fill the vias again?
>
> Bruce Cannon
> Style Management Systems
> http://siliconcrucible.com
> (510) 787-6870
> 1228 Ceres ST Crockett CA 94525

I guess to stop possible corrosion in the hole, and because it
electrically joins the top and bottom layers of the board without
relying on the PTH mechanism that may fracture. ??
-Roman

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