Effects of Ultrasonic Cleaning
Autor: Marcelo Chirai | Publicado: 2017-01-19T21:09:00-02:00


April 12, 2016


Effects of Ultrasonic Cleaning 

http://www.circuitnet.com/experts/52525.html
Does ultrasonic cleaning have an adverse effect on crystals or other components on a PCBA?


If there is a negative affect are there any ultrasonic cleaning methodologies that would prevent problems?




K.U. 





Experts Comments










The answer is no. The answer is yes.

Take your pick. There are two schools on this subject. Smart, 
intelligent, and experienced engineers will tell you that there is 
significant risk of component damage when exposed to ultrasonic energy. 
From damaged crystals to wire bond fractures, that fact
 is that there is the possibility of damage. In fact, several years ago,
 a major assembler of electronic assemblies published data linking 
component damage to ultrasonic energy.


In reality, while the above statements are true, the chance of component
 damage on modern ultrasonic cleaning equipment is rare. Modern 
ultrasonic cleaning equipment utilizes frequencies of 40 kHz. The 
frequency is "swept" up and down to reduce potential component
 damage. Also, if the watts to fluid volume is low enough, damage will 
be further reduced.

Here's the real issue. It doesn't really which school of thought you 
subscribe to. What matters is what your customer, QC manager, 
reliability engineer, and others think.


The
 fact that there is legitimate belief that ultrasonic energy has the 
potential to cause component damage normally precludes it from being 
used to
 preform a defluxing process. 

The
 fact that you are asking this question, illustrates my point that 
ultrasonic energy is not openly accepted in the defluxing world, despite
 compelling
 arguments to the contrary.

I would strongly recommend spray-in-air technology for your cleaning / 
defluxing requirements. It is universally accepted as the conventional 
wisdom for defluxing applications and is never suspected of contributing
 to component damage.















Mike Konrad
President
Aqueous Technologies
Mr.
 Konrad has been in the electronic assembly equipment industry since 
1985. He is founder and CEO of Aqueous Technologies Corporation, a 
manufacturer of automatic de-fluxing
 equipment, chemicals, and cleanliness testing systems. 





We have several published articles available for download on our
web site,&nbsp;click on the
 "Recommended Reading" button. 

The article by B.P. Richards et al. "Does
 Ultrasonic Cleaning of PCBs Cause Component Problems: An Appraisal"
 best addresses your question: "Does Ultrasonic cleaning have an adverse
 affect on crystals
 or other components on a PCBA?" My paper, "Reducing the Cost of 
Misprinted PCBs", addresses the parameters that would help prevent 
potential problems.

I also recommend the IPC-7526, "Stencil and Misprinted Board Cleaning Handbook."















Bill Schreiber
President
Smart Sonic Corporation
Mr.
 Schreiber developed the original ultrasonic stencil cleaning process in
 1989. Obtained the only EPA Verification for specific parameters of 
Environmental Safety, User Safety
 and Cleaning Efficiency for a stencil cleaning process. 





If the frequency of the crystal matches the frequency of the ultrasound, then there is resonance and the component can fail.

Regular cleaners are better than ultrasonic cleaners precisely for this reason.















Karthik Vijay
Technical Manager - Europe
Indium Corp.
Currently
 with Indium Corporation and responsible for technology programs and 
technical support for customers in Europe. Over 15 yrs experience in 
SMT, Power, Thermal &amp; Semiconductor
 Applications. Masters Degree in Industrial Engg, State University of 
New York-Binghamton.






In
 the early days of integrated circuits, say the 1960s and 1970s, 
ultrasonic cleaning was generally not used for cleaning components. The 
affect was
 not on the crystals or components themselves, but on the leads going 
through the packaging.


Repeated,
 high-powered ultrasonic cleaning simply vibrated the leads too 
strongly, causing metal fatigue and component failure. This was 
particularly
 true for military and aerospace systems, which actually banned 
ultrasonic cleaning in one of the now-long-forgotten mil specs.

Modern
 ultrasonic cleaners use "sweep" frequency management to avoid this 
problem. The machines change frequency constantly, so the energy is 
never
 on a harmonic frequency of the lead for very long, and never at the 
same power setting, which has been proven to minimize damage to 
components.


At
 the same time, I think every expert would urge careful and thorough 
testing on your boards, your components and your systems before 
certifying the
 process to be trouble-free.

A
 better answer might be to look at vapor degreasing. Vapor degreasing is
 a much gentler form of cleaning that does not need ultrasonics to work 
well.
 Check out one source at Micro Care, Why is Cleaning With Vertre Better than Cleaning With Water
 or Some Other Solvent ? or&nbsp;another option is
Does MicroCare Have Any Solvents Suitable for Use in Vapor Degreasers?















Mike Jones
Vice President
Micro Care
Mr.
 Jones is an electronics cleaning and stencil printing specialist. 
Averaging over one hundred days a year on the road, Mike visits SMT 
production sites and circuit board
 repair facilities in every corner of the globe, helping engineers and 
technicians work through the complex trade-offs today's demanding 
electronics require.