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October 2002

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From:
Mike Fenner <[log in to unmask]>
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Date:
Mon, 14 Oct 2002 17:08:43 +0100
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Adding phosphorus as an anti-drossing control can be effective for a few
hours until the phosphorus burns out, precisely how long is related to
temperature and how much disturbance you give to the pot. At 340 C I would
expect the time to be quite short. There are some proprietary alloys claimed
to have lower drossing for this type of application.

I shouldn't think any organic chemical such as an oil or wax is going to
last very long at over 300C. Most likely they will contribute to your dross
problem by becoming slag.
You could consider nitrogen inerting which will also tend to increase the
surface tension of the solder.

Placing precise beads of solder on wires is commonly done but not so far as
I know by solder pot dunking. Slow blow fuses are a good example of this
application and where a degree of precision is required, but you would need
to change your technique entirely to do this. Might be worth waiting to see
if other Technetter have some ideas before going down that road.

Regards

Mike Fenner

Applications Engineer, European Operations
Indium Corporation
 T: + 44 1908 580 400
M: + 44 7810 526 317
 F: + 44 1908 580 411
 E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jos Groffils
Sent: Monday, October 14, 2002 3:06 PM
To: [log in to unmask]
Subject: [TN] solder deposition by dipping


Hello,
Maybe this question is not typical Technet-related, but I think I can find
some solder-expertise on this forum.

By quickly dipping a copperwire of 0.6 mm in a HighMeltingPoint-solderbath
(MP=296 -302°C), we succeed to take up 5 to 15 mgr (±1 mm(superscript: 3))
solder at 5 mm from the end of the wire (our target is 10 mgr). Because
this is a non-equilibrium process the spread is rather high. Nevertheless
we try to improve the reproducability. Important factors which we can
control are:  temperature and  withdrawal speed . Surface tension
(influenced by the flux) and viscosity of the solder must be important too
but difficult to measure and to influence.
I can use any ideas / considerations / information how we can improve the
reproducability.

some other related questions:
-how long works the addition of 100 ppm Phosphor in the solder ?
-which could be the influence of eutectic solder (Pb(subscript: 97.5)Sn
(subscript: 1)Ag(subscript: 1.5)  MP=309°C) versus paste range solder (HMP
Pb(subscript: 93.5)Sn(subscript: 5)Ag(subscript: 1.5)  MP=296-302°C) on the
solidifying and reproducability on the wire?
-we use flux to dip the wire and a scraper to evacuate the dross (lot of
dross!) on the solderbath-surface, we do not know a soldercover(oil) except
the too agressive ammonium-zinc-chlorides; are there alternatives? Bath is
operating at 340°C.
-are there alternative droplet depositioin techniques: what about droplet
deposition by jetting? Feasable?

Thanks in advance,
Jos
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