Water Batch Cleaners

We are anticipating switching from RMA to OA flux for both reflow and wavesolder in the next few months. If you use a batch cleaner running DI water only I would like to hear your experiences. How is it for cleaning under low standoff components like TSOPs? Any advantage with spraying from the side as well as top and bottom? Some cleaners have the drying air blowing from the back and others have it blowing from the side of the chamber. Any difference? Any experience you can share is much appreciated.

Thanks,

Bob

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Very good questions Bob� Given the fact that my company is a manufacturer of batch cleaning equipment, I will speak more in general terms rather than in specific terms.

There are several criteria used in the evaluation of batch aqueous cleaning systems. Some of which would not be appropriate for this non-commercial forum (manufacturer's support, quality, etc).

In the world of spray-in-air batch-format aqueous cleaning systems, you may choose from either two-sided or four sided spray systems. We happen to manufacture both formats (I only say this to validate my next comment). I would NOT recommend a two sided spray system for high-density, low profile SMT applications (not even ours).

Populated boards are three dimensional products. A two sided spray system can only provide two angles of attack (this is not true with in-line machines as the boards are presented to the spray almost perpendicularly). A four sided spray system eliminates the potential of shadowing by providing four distinct angles of attack. A study by Raytheon, which compared two and four sided spraying systems, confirms the above statement.

In addition to the two -vs- four sided spray concern, you should also pay attention to the type of spray nozzles used in the batch cleaner. As a general rule, nozzles are defined as follows:

Spray Pattern GPM Pressure

Spray Pattern. The actual spray pattern of the nozzles are vitally important. On most two sided spray systems, a "FAN" spray pattern is used. On four sided spray systems, "FAN" sprays nozzles are used on both upper and lower manifolds while "FULL-CONE" nozzles are used on the side mounted manifolds. In either nozzle design, fine water diffusion is the key to proper under component penetration and impingement.

GPM / Pressure. There are two trains of thought regarding pressure and flow (GPM). Some batch technologies use a "flooding" technique (high flow, low pressure). This is ideal on through-hole boards with "drive-through" stand-off heights. Surface-Mount components however, require more pressure than flow. For through-hole applications, a system with course nozzles works well (50 - 60 GPM, 20 - 30 PSI). For surface-mount applications, I suggest 15 - 20 GPM, 60 - 90 PSI).

As far as drying is concerned, it really does not matter if the drying ducts are mounted on the side of the unit or the rear of the unit. What is most important is that both the intake and exhaust ducts are mounted on the same side of the unit. This action causes full and complete air recirculation and maximum turbulence. Other "benchmarks" of the drying capability of a batch aqueous cleaner are the blower's CFM and air heater wattage.

I hope this helps,

Mike

| We are anticipating switching from RMA to OA flux for both reflow and wavesolder in the next few months. If you use a batch cleaner running DI water only I would like to hear your experiences. How is it for cleaning under low standoff components like TSOPs? Any advantage with spraying from the side as well as top and bottom? Some cleaners have the drying air blowing from the back and others have it blowing from the side of the chamber. Any difference? Any experience you can share is much appreciated. | | Thanks, | | Bob |

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| We are anticipating switching from RMA to OA flux for both reflow and wavesolder in the next few months. If you use a batch cleaner running DI water only I would like to hear your experiences. How is it for cleaning under low standoff components like TSOPs? Any advantage with spraying from the side as well as top and bottom? Some cleaners have the drying air blowing from the back and others have it blowing from the side of the chamber. Any difference? Any experience you can share is much appreciated. | | Thanks, | | Bob | Bob

Try http://www.precisioncleaningweb.com In either the February or March issue of this journal, there is an article titled "Cleaning LCC Assemblies" Authored by Linda Woody of Lockheed Martin.

I recommend reading this before you jump.

Regards Graham

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| We are anticipating switching from RMA to OA flux for both reflow and wavesolder in the next few months. If you use a batch cleaner running DI water only I would like to hear your experiences. How is it for cleaning under low standoff components like TSOPs? Any advantage with spraying from the side as well as top and bottom? Some cleaners have the drying air blowing from the back and others have it blowing from the side of the chamber. Any difference? Any experience you can share is much appreciated. | | Thanks, | | Bob |

Just a question for the forum, and for you Bob......(and yes, it is intended to stir up some debate).

Have you considered testing a higher end dishwasher for your batch requirements (i.e. kitchenaid)? You know, you can supply DI to a dishwasher, too.......

Am I the only one who's benchmark tested cleaning ability of the big in-line and batch guys against a regular 'ole dishwasher? The high end guys use stainless in the tubs, and for the spray arms.......

If you use easily cleanable OA chemistry in SMT and Wave, this might get you by if you do small batches......and it is economical.

Might be interesting to do this test; I admit I have dated test results.....

Scott Cook

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| | We are anticipating switching from RMA to OA flux for both reflow and wavesolder in the next few months. If you use a batch cleaner running DI water only I would like to hear your experiences. How is it for cleaning under low standoff components like TSOPs? Any advantage with spraying from the side as well as top and bottom? Some cleaners have the drying air blowing from the back and others have it blowing from the side of the chamber. Any difference? Any experience you can share is much appreciated. | | | | Thanks, | | | | Bob | | | | Just a question for the forum, and for you Bob......(and yes, it is intended to stir up some debate). | | Have you considered testing a higher end dishwasher for your batch requirements (i.e. kitchenaid)? You know, you can supply DI to a dishwasher, too....... | | Am I the only one who's benchmark tested cleaning ability of the big in-line and batch guys against a regular 'ole dishwasher? The high end guys use stainless in the tubs, and for the spray arms....... | | If you use easily cleanable OA chemistry in SMT and Wave, this might get you by if you do small batches......and it is economical. | | Might be interesting to do this test; I admit I have dated test results..... | | Scott Cook | | Hey Scott,

Good posting. However, what test did you perform and what was the nature of your technology?

You are absoluteley right - if you get great results by hosing the circuits down against a wall - cheap and easy. You might want to cut down on your waste?

Seriously though, it is important to determine the correct specification for your environmental testing. Of course, the nature of your product is highly relevant - Imagine, the auto-lock on your car stops working, maybe it's only an irritation if you campare it to the guy watching the latest Cruise missile launch with an armed nuclear warhead - "anyone see where it went?" Arghh!

Here's listening to you... regards Graham

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| Hey Scott, | | Good posting. However, what test did you perform and what was the nature of your technology?

Both ionics (SMD600) and SIR on RF product to the 3 Gig range. Power amps and Xceivers.

Technology was mixed; double sided SMT. My bare boards measured < 10 mg NACL / in squared, and my results after all processes and cleaning were < 14.

Component technology ranged from 0603's to 20 mil 208 pin QFP's. Fairly dense population. DOD requirements.

Chemistry was Alpha all the way; WS609 paste. Used Aim core no-clean at touch-up.

Testing included active (power on) thermal cycling and humidity cycling for functional test. Also performed salt fog testing.

| | You are absoluteley right - if you get great results by hosing the circuits down against a wall - cheap and easy. You might want to cut down on your waste?

Well, I admit that I did test the spray pressures and angles......

| | Seriously though, it is important to determine the correct specification for your environmental testing. Of course, the nature of your product is highly relevant - Imagine, the auto-lock on your car stops working, maybe it's only an irritation if you campare it to the guy watching the latest Cruise missile launch with an armed nuclear warhead - "anyone see where it went?" Arghh!

True enough. But in the punch and crunch throw away consumer electronics side of things, I present a viable alternative.

Scott

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