What is United States cleaning. Is that something you do after 4th July?
And what is special about United States transducers,
are they better than english?
Erh..hmm..(cough)..hrrrm..
Brian, if you use a solvent as agitation media, won't the lowest temperature
theory collide with the fact that higher temperature increases the
solubility? If we use isopropanol for flux removal, what would be the best
compromise?
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brian Ellis
Sent: den 6 juli 2005 10:29
To: [log in to unmask]
Subject: Re: [TN] Ultrasonic Cleaner
OK, lesson on US coming up, sorry for the simplistic didactic matter! :-)
How does US cleaning work? You apply a mechanical vibration to the
liquid, which is virtually incompressible. When the pressure rises, the
fluid is pushed and the level rises (imperceptibly, of course). When the
pressure decreases, minute cavities form where there are nuclei. These
are essentially vacuums, but they do contain vapour, as well. At the
next positive pressure, the mechanical inertia of the mass of fluid is
too great for the cavities to be refilled. At the next negative
pressure, the cavities which are still present form the nuclei for the
cavitation and they thus grow bigger. After n cycles, the cavity will
have grown to a critical size and, being essentially a vacuum, they
collapse instantaneously (in picoseconds). This causes the vapour to be
adiabatically compressed, resulting in an astronomical temperature rise,
often of the order of thousands of degrees. The heat is dissipated in
the solvent and the energy contained therein becomes a mechanical shock
wave, a micro-tsunami if you like, and this shock wave is what scrubs
your parts clean. The effective radius of this scrubbing action is of
the order of µm, so you want the cavitation to occur where the dirt is.
Now, the favourite place for cavitation to occur is on gas molecules
which can be anywhere in the fluid, nowhere near the place to be
cleaned, so the energy is wasted there. This is why the solvent must be
degassed before use. In the case of some organic solvents, such as the
late-lamented CFC-113, applying the US for, say, 15 minutes before
starting to clean would degas the solvent sufficiently. Water (or
aqueous solutions) are a horse of another colour and degassing became a
complex procedure requiring heating and low pressures, then cooling,
before use.
What is the difference between liquid and vapour phases of a substance?
Only the size of the molecule. In an apparently homogeneous liquid, you
actually have some molecules in vapour phase (which is why the liquid
evaporates, as the larger molecules happen to randomly reach the
surface). This is also the motive power for Brownian movement. This is a
question of the equilibrium conditions of the vapour pressure at a given
temperature. The more molecules in vapour phase within the body of the
liquid, the more cavitation nuclei are formed remote from where you want
them, so the cleaning becomes less efficient.
However, it doesn't stop there. The higher the temperature, the more
vapour there is within a cavity and the lower the adiabatic compression
during collapse, resulting in a shockwave of lesser amplitude.
For the most efficient US cleaning, choose the lowest temperature
DEGASSED solvent you can. This is why, in the traditional vapour phase
degreaser, the US transducers are always placed in the cold sump,
receiving the condensate from the refrigerated freeboard condensers and
never in a heated sump.
I hope this makes it clear.
Brian
Dehoyos, Ramon wrote:
> I plead ignorance on this matter. I was taught that the fluid *had* to be heated. Could you enlighten us please?
> Thanks Brian,
> Ramon
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Tuesday, July 05, 2005 10:24 AM
> To: [log in to unmask]
> Subject: Re: [TN] Ultrasonic Cleaner
>
> You do realise that US cavitation becomes less effective if you heat the solvent, do you?
>
> Brian
>
> David Tremmel wrote:
>
>>Happy 4th Everyone,
>>
>>I am in the market for a benchtop ultrasonic cleaner and am interested
>>in purchasing a Branson 1510DTH (1/2 gallon capacity with a heater).
>>
>>It will be removing post-reflow flux residue from stencils and other
>>equipment and will be operating 5-10 hours per day.
>>
>>If anyone has any experience with this model or has a suggestion based
>>on their experience with another brand and model, please let me know.
>>
>>As always, I appreciate whatever feedback I receive.
>>
>>David
>>Technical Manager
>>BT Mexico
>>
>>_________________________________________________________________
>>Consigue aquí las mejores y mas recientes ofertas de trabajo EE.UU.
>>http://latino.msn.com/empleos
>>
>>---------------------------------------------------
>>Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
>>unsubscribe, send a message to [log in to unmask] with following text in
>>the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt
>>or (re-start) delivery of Technet send e-mail to
>>[log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing
>>per day of all the posts: send e-mail to
>>[log in to unmask]: SET Technet Digest
>>Search the archives of previous posts at:
>>http://listserv.ipc.org/archives Please visit IPC web site
>>http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
>>information, or contact Keach Sasamori at [log in to unmask] or
>>847-615-7100
>>ext.2815
>>-----------------------------------------------------
>>
>
>
> --
> ______________________________________________
> Please note new e-mail address [log in to unmask]
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
> -----------------------------------------------------
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
> -----------------------------------------------------
>
--
______________________________________________
Please note new e-mail address [log in to unmask]
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
