🗹 Time for Fact Checking

On the test bench: Do linear spray systems clean better than rotating ones?

🗹 Time for Fact Checking

On the test bench: Do linear spray systems clean better than rotating ones?

„“The higher the spray pressure, the better the cleaning results? With No Clean production, cleaning is generally not needed? Always shadowing in batch machines? Spray processes are better than dip tanks“

Did you ever come across these questions about electronics cleaning? ZESTRON checked these myths scientifically -independently from machine manufacturers, technically well founded and transparent. Convince yourself.

A frequently heard statement says that cleaning systems with linear spray arms would be better than systems with rotating arms. Because only linear systems would deliver reproducible results.
But let’s first look at the cleaning principle of both systems.

▸ Functionality of both systems

cleaning pcbIn case of a linear system, the spray arm moves evenly over the substrates;
in case of a rotating system, the spray arm rotates over the substrates.


▸ Linear System:

lineare anlage elektronikreinigungThe linear movement of the spray arm suggests, that all parts receive the same volume of cleaning agent for the same time span.

Mathematically speaking, the volume of cleaning agent hitting a specific area in a time interval, is equal to a nozzle and arm specific constant divided by the linear velocity across the specific area multiplied with the number of passages of the arm in the time interval.

In a linear spray system the spray arm velocity is the same for every location, hence the specific volume is equal everywhere and the parts A1 and A2 see the same conditions.

▸ Rotating System:

Rotationsanlage reinigung LeiterplattenIn a rotating system the nozzles at the ends of the spray arm rotate around a bigger circle than the nozzles in the center. So the bigger the circle’s diameter, the bigger the area to be covered by the nozzle with cleaning agent. Assuming that the same volume of cleaning agent comes out of each nozzle, part A2 would get less cleaning agent than part A1.

Scientifically speaking, the velocity across an area is dependent on the angular velocity of the spray arm multiplied with the radius of the area. The previous equation changes and the volume becomes dependent on the radius. In simple terms, the larger the radius, the lesser the volume.

That would mean: While cleaning conditions in rotating systems vary, in linear systems they are the same for every part – regardless of the part’s position in the system.

Does it mean that only linear spray systems deliver reproducible results? What if this myth was true?

  • Does it mean that only linear spray systems deliver reproducible results?
  • Do assemblies in a rotating system not see the same conditions?
  • Are rotating systems then fundamentally worse than linear ones?



▸ The Fact Check:

We selected one cleaning machine with linear spray arms and one system with rotating arms and ran some comparative trials.

We checked the cleaning agent distribution along the spray arms during operation. The cleaning agent volume in the linear system shows hardly any difference between the positions. Whereas in the rotating system, the volume at the center is higher.

By defining a glass test board with test flux and different components and standoffs we were able to check the cleaning performance of both systems under components.

cleaning pcb

▸ The Result:

In thelinear system, the tests show the same, reproducible cleaning results under components of the assemblies in the positions A1 and A2.

In therotating system,the flux residues on the inside positioned assembly are cleaned off significantly faster than on the outside positioned one.

The test results show: Theoretically, the myth that only linear spray arms deliver reproducible cleaning results is true, BUT: Only if the movement of the spray arms is considered in isolation, provided that all other influencing factors on the cleaning process such as spray pressure and volume are identical. But this is not the case with systems on the market.

Are you interested in the trials’ details and would you like to better understand the different systems? Please feel free to contact us for detailled information

Simple and Concise

On the test bench: Do linear spray systems clean better than rotating ones?

The Statement

It is often claimed in the market that assemblies in systems with rotating spray arms do not experience uniform cleaning conditions. It is assumed that the parts are exposed to different cleaning time spans and cleaning volumes depending on their position inside the cleaning chamber. In contrast, the conditions in systems with linear spray arms would always be identical.

The Scientific Review

To check the myth, ZESTRON carried out some comparative tests:

  • Cleaning trials with a linear and a rotating spray system
  • Measurement of cleaning agent volume at different positions in the system
  • Flux removal under components by using a test board

The Solution

Is the myth true or false?

Your contact for fact checking

Are linear spraying systems better than rotating ones?

Request the trial‘s details and find out more about the different systems.

You will receive personal access data to a presentation held by one of our engineers.

Electronic Cleaning Myths – checked by ZESTRON