Brian:
Are you recommending water as the best fluid for US cleaning, or are there better fluids for this purpose? One more question, why is it that the US cleaner manufacturers include a heater in their equipment?
Diverging a little, I have also read in an article that water alone ( no soap ) is a good cleaner of clothes when is US agitated.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Wednesday, July 06, 2005 7:15 AM
To: [log in to unmask]
Subject: Re: [TN] Ultrasonic Cleaner
The best compromise firstly would be not to use IPA which is a mediocre solvent at the best of times! :-) Secondly, IPA in a US sump could be dangerous if the energy levels were high, as it may cause increased evaporation if cavitation occurs near the surface (e.g., with floating contaminants forming nuclei). Thirdly, would hot IPA with no useful US agitation be better than cold IPA with US agitation? As Doug would say, it depends. If the contaminants were readily soluble and the article had a fairly simple topology, I'd go for the hot solvent and no US. If the article had a complex shape, esp. blind holes, then the US may be better. That having been said, best results would certainly be obtained by immersion in boiling solvent, transfer to cold solvent with US and a final rinse in vapour phase. And even better results obtained with water!
Brian
Ingemar Hernefjord (KC/EMW) wrote:
> 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
-----------------------------------------------------
|
