At least one mfr is already making a green coloured LF paste as you

describe.



Regards,

Chris

 

-----Original Message-----

From: Leadfree [mailto:[log in to unmask]] On Behalf Of Emanuel Zimmermann

Sent: 09 November 2005 08:13

To: [log in to unmask]

Subject: [LF] Avoiding Solder Paste Mixup



Hello Experts,



I'm monitoring this forum for a while now and thankfully could learn a

lot

of your expertise.  Since I can't claim beeing expert myself in this

arena

my return is much less.

We just ran into the issue that our assembly house mixed up solder

pastes

and soldered lead containing BGA's with LF paste. Despite the assembly

house assured that they have used Sn/Pb paste I could show that the

solder

joints are LF (with the help of lead test sticks I first heard of in

this

forum).

This made me think for a method how it may be possible to distinguish

between LF and lead containing pastes easily already in the printing

phase

of the paste to the PCB. Has anybody of you spent any thoughts about

this?

What came to my mind was that maybe LF pastes could have some adds that

let them appear in a color, green for example, instead of the metallic

grey. These adds may can evaporate during reflow or even better remain

in

the solder to have colored joints on LF boards and metallic grey joints

on

Sn/Pb boards. Would this be an option?



Thanks for your thoughts,

Emanuel



---

MPL AG                                   www.mpl.ch

Emanuel Zimmermann       [log in to unmask]

Manager R&D                       Phone: +41 56 483'34'34

Taefernstrasse 20               Fax:      +41 56 493'30'20



CH-5405 Daettwil

---



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