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PJ F AOUEOUS CLEANING TECHNOLOGY FOR PRECISION ELECTRONIC PARTS

Yoshihide Shibano, President S 6 C Co., Ltd.

1. WHAT IS ULTRASONIC CLEANING?

Before I speak about our remarkable aqueous ultrasonic cleaning system, let's talk about cleaning systems in general.

I believe there is a great misunderstanding of the technology behind ultrasonic cleaning systems. This lack of understanding is delaying development of a remarkable ultrasonic cleaning technology, a technology which can replace those using CFCs and ethane. So, let's take a look at ultrasonic cleaning.

An ultrasonic cleacing system uses impact waves generated by small water-jets in the cleaning solution, which is produced when cavity created by ultrasonic waves of condensation and rarefaction is broken. ~

In another words, this is a physical cleaning method which is applied by cavity breakage generated by ultrasonic waves. In addition, cavity breaks toward solids on the surface of the solid materials and away from them on the surface of liquids.

There are various forms of cavitation such as circular and linear. These forms are determined by such factors as the bonding strength of liquid molecules, ion dissolved in the cleaning agent.

&vi tat ion Picture taken a t 1/1000th of a second

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So, the ultrasonic cleaning system is a method which uses cavitation impact force generated by ultrasonic waves. Whether you use water, CFcs, or l,l,l-trichloroethane, you must control cavitation otherwise, effective ultrasonic cleaning can't be done. This is why you need to fully understand cavitation.

2 . WHAT IS CAVITATION CONTROL?

Now, let's talk about cavitation control. Cavitation control is performed effectively by the following:

(1) Cavitation generating area control:

The standing waves must be controlled in order to have effective ultrasonic cleaning. Also, effective ultrasonic cleaning can be only performed with proper control of the area and forms of cavitation. Here are various types of cavitation distribution:

a ) Hori zon t a1 distribution b ) Vertical distribution c) Grid distribution d) Oblique distribution e) Globular distribution f) Cylindrical distribution g) Even distribution

a ) b)

C )

k i c dis t r ibut ion for water

Basic d i s t r i b u t i o n for w a t ~ r Basic distributioo f a r water

A Basic distribution for nta I I

Basic distribution for water

Basic distribution for water

( 2 ) Cavitation density control:

This is determined by the ultrasonic waveform, the cleaning solution and sound pressure density.

( 3 ) Cavitation impact force control:

The cavitation impact force is proportional to the pressure and is inverse to steam pressure and frequencies of water as a cleaning agent. Additionally, various factors determine the cavitation impact force.

( 4 ) Cavitation generating efficiency:

How to generate and use more cavitation by using the same amount of energy. That's the challenge we face in this area.

We at S h C have performed extensive research and experimentation into cavitation control technology as a basic technology, such as those I just mentioned, to develop an efficient ultrasonic cleaning system.

We are confident that we can provide you with the best cavitation control technology and lots of technological data on systems as well as on our performance record.

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3. WHAT IS AN ENHANCED CAVITATION SYSTEM?

Now, let's examine ultrasonic cleaning systems using C F C s . Many visible bubbles are seen on the ordinary ultrasonic oscillator and you can see them breaking on the surface of the CFC cleaning agent. These visible bubbles are N' and 0', that is. air bubbles.

If we say the phenomena of cavitation breaking is ultrasonic cleaning, air bubbles generated in the system must break somewhere. However, they don't break in the cleaning solution. Therefore, there is no cavitation in this case.

This is not the only disadvantage of ordinary ultrasonic cleaning with CFCs. The most common factor in cutting off ultrasonic waves is air bubbles and coarse meshes. The strainers cut off ultrasonic waves, Air bubbles are often used as a effective method to shut off ultrason'lc waves as well.

Here's my conclusion: It is so obvious that ordinary ultrasonic cleaning using CFCs doesn't generate cavitation which is the primary factor in proper ultrasonic cleaning, but it does absorb and shut off all ultrasonic waves thus producing only air bubbles.

Air bubbles are not visible during properly performed ultrasonic cleaning using CFCs. In fact, air bubbles generated by ultrasonic waves cannot usually be seen during any type of ultrasonic cleaning regardless of the cleaning so 1 uti on.

Most of the energy in the ordinary ultrasonic cleaning system using CFCs is wasted on vacuuming air from the cleaning solution. As a result of this, little energy is used for actual cleaning purposes.

Unfortunately, this is still a reality for ordinary CFC ultrasonic cleaning systems used worldwide.

I wonder if we could call this an effective ultrasonic cleaning system. We at S 6 c don't sell any CFC ultrasonic cleaning systems. What I have been telling you here isn't limited to CFCs. It's the same for any liquid cleaning solution. Again, cavitation is essential for these systems to perform properly.

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All cleaning solutions such as C F C s , l,l,l-trichloroethane, alcohol, gas oil, water and pure water are manipulated by ultrasonic waves in basically the same way.

All types of liquid solutions can be superior air absorbent. So, if necessary, air must be removed from the liquid to perform effective ultrasonic cleaning.

The amount of air contained in the liquid plays a definite role in the interaction between liquids and ultrasonic waves.

Our S & C Enhanced Cavitation System is one which uses cavitation properly and controls the amount of air in the cleaning solution. This enhances the cavitation's efficiency and provides peak performance.

I would like to explain to you how the aqueous ultrasonic cleaning technology has been progressing and our performance record with our cleaning system.

In addition, cavitation impact force is increased substantially and cleaning power improves as well.

When the DO value is changed to 0.5 - 2 ppm, standing waves can't be found anywhere, because the standing waves are now spread evenly everywhere. In this case, there is nothing to prevent ultrasonic waves from forming and most of the standing waves can be altered to cavitation.

These are ideal conditions for effective ultrasonic cleaning with water. This is also the on ly condition where water is a more superior cleaning tool than CFCs.

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G v i tation Enlargement of picture taken 1/1000th of a second

Cavitation distribution

. , . .

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4 . WATER & ENHANCED CAVITATION SYSTEMS

Water usually contains 6 - 8 ppm of oxygen and 14 - 16 ppm of nitrogen. Let's examine the horizontal standing waves of cavitation in the water with 6 - 8 ppm oxygen.

In this case, there are horizontal standing waves at 114 the ultrasonic wavelength from the surface of the liquid to the bottom of the oscillator, where high density cavitation is generated, and at 112 the ultrasonic wavelength from the surface of the liquid, secondary waves exist.

A third series of waves exists further down at 1 / 2 of the remaining wavelength. From here, waves are generated every 112 the distance of the remaining ultrasonic wavelength.

In fact, the power of cavitation is weakest and its cleaning power at its lowest in the situation I just described. However, this describes ordinary ultrasonic cleaning using water.

When the DO (dissolved oxygen amount) value is changed to 3 - 4 ppm, large fluctuations in cavitation distribution are present. Standing waves still exist, however, boundary lines between the first, second and third waves are gradually fading away.

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5. ENHANCED CAVITATION SYSTEM EXPERIMENTATION ,.

At the DO value of 0.5 - 2 ppm, once ultrasonic waves are generated, even if the distance is 1-meter between the ultrasonic cleaning oscillator and the liquid surface, many small waves are seen on the surface of the liquid and numerous tiny ultrasonic splashes of water are present.

In the above condition, the liquid squirts out 1 - 2-meters through a nozzle with 20 p - 100 holes onto the surface of the liquid. Its force is so strong, it can easily make holes in aluminum bowls.

This force can be harnessed to de-burr various manufactured parts and products.

We control cavitation in this case and use it for electronics cleaning and machine-processed parts cleaning.

The following are some examples:

6. ENHANCED CAVITATION SYSTEM APPLICATIONS

1) Current relay wash ultrasonic cleaning system: ~

This system is equipped to wash and dry an entire small sized relay unit with pure water.

No. 1 tank: Pure water, enhanced cavitation system Ultrasonic frequencies of 40 KHz, 100 KHz, and 200 KHz are generated concurrently.

No. 2 tank: Pure water, enhanced cavitation system Ultrasonic frequencies of 40 KHz, 100 KHz, and 200 KHz are generated concurrently.

No. 3 tank: Air blow, warm air

No. 4 tank: Vacuum dry

The small sized relay unit is equipped with four movable circuits and a coil. Approx. 20 mm x 30 mm x 15 mm

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.. Profile:

We at s & C performed the test washing 100 to 3 0 0 units of these small-sized relay units. The test showed better performance than with systems using C F C s in the amount of contaminant, electric characteristics and drying performance. Of course, operating costs are low.

2 ) Rosin flux removal on Precision PCB:

No. 1 tank: Special cleaning agent, Enhanced cavitation system Ultrasonic frequencies of 40 KHz, 100 KHz, and 2 0 0 K H Z are generated concurrently.

No. 2 tank: Pure water rinse

No. 3 tank: Pure water, enhanced cavitation system Ultrasonic frequencies of 40 KHz, 100 KHz, and 200 KH z are generated concurrently.

No. 4 tank: Air blow, warm air dry .

Ultrasonic cleaning systcm

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Besides PCB flux, IC flux can be removed with this type of system. Depending on the degree of cleaning required, the number of rinsing cycles will vary.

Of course, the amount o f washed particles and carbon left in the cleaning solution, and the electrical characteristics of the system are far superior than those using CFCs. Additional vacuum dry processes may be used to enhance the finished product.

3 ) Molded plastic parts cleaning:

No. 1 tank: Pure water, Enhanced cavitation system Ultrasonic frequencies of 40 K H z , 100 K H z , and 200 KH Z are generated concurrently.

No. 2.tank: Pure water, Enhanced cavitation system Ultrasonic frequencies of 40 KHz, 100 K H z , and 200 K H Z are generated concurrently.

No. 3 tank: Air blow, warm air

No. 4 tank: Air blow, warm air

Rotation type cleaning basket

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30% of our orders are for cleaning systems that use no chemical agents whatsoever: NO CFCs, NO chemical cleaning agents and NO surface active agents. They use only water or pure water. This trend is increasing.

50% of those systems using CFCs as a cleaning agent can be converted to the Aqueous Enhanced Cleaning Systems.

The remaining systems can use a combination of surface active agents and the enhanced cavitation system to end the use of CFCs.

~ ---+ Currently, this system processes plastic precision molding parts in the 600 mm x 6 0 0 mm x 500 mm basket in three ( 3 ) minutes.

4 ) Barrel processed parts cleaning:

Basically, the process is the same as the one used for molded plastic parts ,except this process doesn't use any cleaning solution other than water. NO CFCs or ethane are used.

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. 5 ) Lapping parts Cleaning:

No. 1 tank:. Cleaning agent, Enhanced cavitation system Ultrasonic frequencies of 2 8 KHz, 100 KHz, 200 K H z are generated concurrently.

No. 2 tank: Water Ultrasonic frequencies of 2 8 KHz, 100 KHz, and 200 KHz are generated concurrently.

No. 3 tank: Water Ultrasonic frequencies of 2 8 KHz, 100 KHz and 200 KHz are generated concurrently.

No. 4 tank: Air blow, warm air

We can guarantee better results in lapping cleaning with a two ( 2 ) minute tact cleaning in S & C ' s system as opposed to placing the same item in a CFC cleaning system for one day.

However, we must be sure to use the ultrasonic frequencies at the concurrent ,28 KHz, 100 KHz and 200 KHz rates for this purpose.

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S 6 C ' s enhanced system can be used for materials which are easily rusted such as bearings and sintering without using an anti rust agent simply by lowering the value of DO.

There are so many examples that I can show you. We at S 6 C sold more than 100 fully automated aqueous cleaning systems which replace cleaning systems using CFCS and ethane. We are also patenting our products in the US.

6. LOOKING TO THE FUTURE:

Water is a superior cleaning tool, however it has not been used much in the past. The S E. C enhanced cavitation system brings ultrasonic wave efficiency to a peak and can be used in a broad range of cleaning applicatlons, such as acid cleaning, de-burring and of course ordinary cleaning.

Our system has proven to be an effective replacement to

As a result of rapid developments in aqueous cleaning technology and widespread peripherals, we now believe that we have already developed an environmentally friendly aqueous cleaning technology. And, we are prepared to make these systems available for widespread use.

I believe that the best alternative to C F C s and ethane is WATER.

S b C ' S enhanced cavitation system will play a key role in the environmentally friendly aqueous cleaning system.

If YOU would like for information about our products, please stop by Booth l t 2 2 0 .

cleaning with C F C s and even ethane.

Water is superior.

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