For me, the important things are a) there must be no water puddling
between the components (i.e., instantaneous draining; if it occurs, it
will dissipate the kinetic energy of the jets before the water can do
any work under the components b) the jets should impinge at an acute
angle to the plane of the board, to ensure there is max ingress under
the components c) the angle of impingement must vary d) there must be no
shadowing e) the wash must have solid jets and the rinses very fine
sprays (water droplet diameter < smallest under-component space) f) the
pressure is relatively unimportant: it is the energy imparted to the
water that counts. As a rule of thumb, you need ~2 kW of pump for every
metre of wash bar. Too high a pressure can even be negative because the
water tends to bounce off the surfaces. This is the voice of experience
as an ex-maker of aqueous machines. See my book for more details. g) the
number of rinses should be sufficient to ensure several replacements of
water under the tightest component. h) high speed (>200 km/h) air knives
form an essential part of the cleaning process, also impinging at an
acute angle, to blast residually contaminated water from under the
components.

Brian

John Parsons wrote:
> We are looking at adding to our current batch washer (Older Aqueous Tech
> unit) and I am interested in hearing some thoughts as well as first hand
> experience on how the following two cleaning systems work with regards
> to low profile (BGA's etc.) devices run as both conventional and
> lead-free processes.  We are currently running water soluble flux and
> are not using saponifiers for the cleaning process.  I have listed the
> two machines we are considering along with my thoughts.  I am interested
> in hearing yours.
>
>
>
> Aqueous SMT1000
>
> -         dish washer style loading, poor loading = poor cleaning
>
> -         vertical loading improves throughput
>
> -         high pressure pumps 120psi wash, 45psi rinse for leadfree but
> can this style of machine effectively clean under BGA devices?
>
>
>
> Electrovert Aquajet
>
> -          large cleaning area (30x30") but horizontal loading would
> appear to limit throughput.
>
> -          Is any racking available for this machine to process boards
> vertically for increased throughput (within height limitations of front
> opening) or does design technology reduce cleaning cycle when compared
> to Aqueous machine thereby somewhat offsetting loading capacity.
>
> -          wash and rinse technology coupled with horizontal loading
> seems that it would do a significantly better job on cleaning under low
> profile devices
>
> Regards,
> John Parsons
>
>
>
>
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