Tony :
The nozzles you refer to being all plastic , and as such
subject to excessive wear. The whole idea of the self cleaning is it
requires pressure to push the inner portion of the nozzle which forms the
orifice when operating into proper position. When pressure is removed the
inner portion springs back and opens . First this takes force. Second you
have moving parts , if you have moving part you have friction and an area of
close fit where fine particles can lodge or wear the mating surfaces. I
never had any luck with them for consistent spray patterns and or droplet
size, and when the solution got loaded , they still clogged.
If I was going to use them today , it would be in a water rinse
section only. and only then if I didn't have conventional nozzles. They
would be great in very large sizes for cleaning tanks, or quenching steel
and such where you couldn't afford to have a clogged nozzle.
My experience is that you will get the most for you buck if you
spend money on positive filtration systems for the equipment in question.
Bag, or plate housings are the best for high flow rates. cartridges are
readily available and easy to change.
What ever form you pick , you will find that with a good positive
filtration ( ie one that all of the solution must pass through) consistency
of process is improved and some defects are diminished.) Just think about
it , take a developer for example , most have only a window screen to keep
the chunks out , but yet we deal with features considerably finer than the
mesh. Just for your information , I recommend a maximum filter size of 0.5
of the nozzle orifice diameter, or the smallest geometry to be processed
which ever is smaller. Thus if you have a developer with say Spray Systems
HVV 5005 nozzles ( 50 degree , 05 orifice size ) , the Equivalent orifice
diameter is 0.057" or about 1400microns divided by 2 for a filter size of
700 microns, since for example I want to clear holes say 0.010" ( 250
microns ) , then I want a filter 250/2 =125 or the next common size
100micron.
With any given nozzle size, if you increase the pressure you decrease the
droplet size, improve the spray pattern, velocity, and impact. the same is
true as the solution rises in temperature. the item that will degrade the
effects of pressure and decrease spray pattern, velocity, impact and
increase droplet size is an increase in viscosity.
Hope this helps , If you need further assistance let me know
Russell Smith
[log in to unmask]
----------
From: Tony Steinke
To: [log in to unmask]
Subject: [TN] SPRAY NOZZLES
Date: Wednesday, September 27, 2000 10:24AM
Good day fellow technetters,
We are a manufacturer of PCB's.I am currently in the process of replacing
old, worn nozzles in several areas of the wet process area and was wandering
if anyone out there has had any experience with
self cleaning nozzles from a manufacturer called Laidler. My question is are
they really self cleaning or
am I throwing money into a product for no reason for the nozzles are quite a
bit pricier than original
equipment manufacturer. Any input would be greatly appreciated.
Tony Steinke
Process Engineer
[log in to unmask]
Circuit Technologies
3622 Clearview Parkway
Atlanta, GA 30340
(770) 458-1700
www.cir-tech.com
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