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March 2003

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From:
Mike Fenner <[log in to unmask]>
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Date:
Tue, 25 Mar 2003 14:29:17 -0000
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Thanx Brian.

Reminds me.....I used to carry around squares of Kleenex that had been
roller tinned.  They looked just like a piece of tinned copper right up till
you poked them with a soldering iron.

Saved hours of discussion about solderability.

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 Brian Ellis
Sent: Tuesday, March 25, 2003 8:27 AM
To: [log in to unmask]
Subject: Re: [TN] Roller Tinned PCB's


Mike

The others have not really answered what roller tinning is. Imagine a
trough of molten solder, in which an iron drum is rotated with a
peripheral speed of about 10 or 15 cm/s. On top of the iron drum is a
heat-resistant "rubber" roller. The drum is tinned with the solder, with
the aid of an active water-soluble flux. The PCBs are dipped into the
same flux and fed between the drum and the roller, copper side down.
This transfers some of the tinning onto the copper. This is the basis of
roller tinning.

The thickness of the tinning is microscopic and is really only the
intermetallic layer with an admixture of iron, except that a blip of
thicker solder is left on the trailing edge of each conductor (much
worse than the uneveness of HASL). It was used for both single and
double (2 passages) sided circuits before plating-through of holes was
common, often the holes equipped afterwards with some form of rivet.
Obviously, it was useless with PTHs, because there was insufficient
tinning on the drum to enter the holes: this was the real cause for its
demise.

The quality of protection was fairly mediocre, solderability being
maintained for only 2 or 3 months, because of the thinness of the
coating. Notwithstanding, it was a very popular, cheap, coating in its
heyday. It was not replaced by HASL, which came later, but by tin-lead
plated boards initially, followed later by hot-oil and then infra-red
fusion. About the same timeas the late days of roller tinning was the
forerunner of HASL, the Hydrosqueegee. This called for passing the bare
boards over a solder wave and then immersing them in a violent spray of
hot oil to level off the excess and clear the holes, even PTH. This was
not very popular because the smell was atrocious and the machines were a
fire hazard.

Brian

Michael Bell wrote:
> Hi all,
>
> Just a little stumped on terminology here, what is "Roller Tinning".  What
> is the specific differences between this method and HASL???  Are there any
> specific pros/cons for the Roller method???  Any information would be
> appreciated.
>
> Cheers
>
> Mike
>
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