RE: [CAD_CAM_EDM_DRO] Pick and Place question

Jon

Do you know a little more about the paste.

Reason I’m asking, a pot of solder paste must be at least 10 times a reel of
solder. Over in the UK 500G of leaded solder is about £7, lead free was £20
but I can now get that for £12, but solder paste they want £70 for 40gms, I
presently buy mine from China.

Lead free is going to have tin and silver in it, I assume alloyed before and
then broken down.

You say the solder is tiny balls, is there a special reason for this rather
than grinding it into a powder.

And flux, what are they using, it must be simple cheap chemicals, but any
idea what?,

Like explosives do I have enough under the kitchen sink plus a bit to make a
good flux for lead free solder. Don’t need to make explosives I’m licensed
for them.



Regs Mark



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: 28 March 2007 18:50
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Pick and Place question



BRIAN FOLEY wrote:

> Hi, i see references to solder paste and then to glue or adhesive. i

always thought the solder paste was used as the adhesive till it was
reflowed...

> perhaps some one can explain if there is a difference? thanks, brian f.

If you want to place components on BOTH sides of the board and
then reflow the solder all at one time, the bottom-side
components will fall off either before or as it is heating up.
So, you put dots of glue under the bottom-side components before
placing thos parts. You then place the bottom components,flip
over and place the top side. The glue is designed to stick
until the solder melts and pulls the part a bit closer by
surface tension.

The solder paste can be trusted to hold the top-side components
in place if the board isn't handled roughly, but that is about
all. Solder paste is a mix of tiny solder spheres and flux,
with a small amount of solvent to make it flow (barely).

Jon





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