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Using isopropanol with DI water for rinsing after washing boards

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#65408

Using isopropanol with DI water for rinsing after washing boards | 9 November, 2011

Hello all,

We have an old batch cleaning machine in our production and we use isopropanol alcohol during the rinsing process probably to lower the surface tension. Right now we are looking for a new machine who can do a better job compare to the old one, but do we have to keep the alcohol during rinsing? Or can we had another substance to lower the DI water surface tension during the rinsing stage? Or just use Di water? Thanks in advance Julien

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#65423

Using isopropanol with DI water for rinsing after washing boards | 10 November, 2011

While you're waiting for others to reply, search the fine SMTnet Archives for similar threads. For instance: * Batch cleaners http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=49334

* Use of IPA as a cleaning agent http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=43349

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#65424

Using isopropanol with DI water for rinsing after washing boards | 10 November, 2011

The use of IPA in automated defluxing systems is nearly extinct for the following reasons:

1. IPA is flammable. In a spray-in-air environment, the already low flashpoint is even lower.

2. IPA is not a great solvent. There are specific containment species that are not solubilized by IPA.

Modern spray-in-air defluxing systems utilize water as a base cleaning material. In a wash cycle, a water-based defluxing chemical is normally added to allow for the removal of rosin and no-clean fluxes. This chemical additive lowers the wash solution's surface tension, allowing adequate under component penetration (impingement). The rinse cycle enjoys no benefit from surface tension reducing chemicals so the machine's hardware must be capable of ensuring impingement purely based on mechanical means.

There are several methods of assuring proper rinse impingement. Some machines use simple high pressure non-diffused "jets" of water which subject the assembly to high impact pressures. Other machines utilize methods to reduce the rinse spray's droplet size to allow adequate impingement with lower impact pressures.

Here are two links to published articles. One on the subject of low-profile defluxing and the other on the importance of the rinse cycle.

What is the most important aspect of de-fluxing? http://www.aqueoustech.com/aquuniv/knowledge-base/Articles/Its%20all%20about%20Rinse.pdf

Cleaning for Reliability Post QFN Rework http://www.aqueoustech.com/aquuniv/knowledge-base/Articles/Cleaning%20for%20Reliability%20Post%20QFN%20Rework.pdf

I hope this helps!

Mike Konrad

Aqueous Technologies

909.291.1141

konrad@aqueoustech.com

www.aqueoustech.com

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#65429

Using isopropanol with DI water for rinsing after washing boards | 11 November, 2011

Thanks guys, But for the cleaning process we already have a chemical product to clean flux residues and other contaminant. But it seems that we can't rinse properly under low stand-off components and we find trace of our chemical under some ceramic capacitor. We don't want to clean with alcohol but just rinsing boards. Does another products exist to lower DI water surface tension?

Edit: We have heard that there is some conferences and workshops about cleaning. But all of these are in america or asia and we are in europe... Do you know if there is similar conferences in europe?

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#65431

Using isopropanol with DI water for rinsing after washing boards | 11 November, 2011

On cleaning under low standoff components: How about reading the papers that Mike kindly posted for you above? It's intended to answer questions about cleaning under low standoff components.

On conferences, exhibitions, and shows: The BIGGEST show on the planet is in Euroland http://productronica.com/en/home/visitors/prices-application/online-ticket-registration?cm=banner&src=mb_USA&cn=prd_2011_registr&sum=prd_11_registr_mb_USA

Hurry

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#65432

Using isopropanol with DI water for rinsing after washing boards | 11 November, 2011

Sure it's big enough! But unfortunately we can't go this year because we have an important customer who come at our plant at this perdiod :-( Probably next year or at SMT in nuremberg...But also it's not only defluxing oriented and only in german.

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#65435

Using isopropanol with DI water for rinsing after washing boards | 11 November, 2011

What is the size of the low standoff components you find trace wash effluent? and, what is the gap from the board to the underside of the component?

If your component has a very low standoff, and/or, a wide footprint, you may want to consider finding a cleaning chemistry that can be used for both wash and rinse...but, this would mean moving away from aqueous cleaning....which you say you don't want to do.

The wash effluent left after washing will act to reduce the surface tension of the rinse solution, allowing penetration and flow underneath the low standoff devices. But, if the remaining wash effluent is hidden from the flow due to the uni-directional flow pattern, then there is not the ability to rinse. So, you may want to try rinsing in different orientations.

Flow pressure may also be a concern, so trying to orient the difficult components closer to the nozzle may help. Or, try laying the board in a way to avoid shadowing.

There is a large cleaning supplier with a large laboratory in Ingolstadt, Germany who probably can assist you for technical and evaluation support. I'll send the contact information off-line.

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#65440

Using isopropanol with DI water for rinsing after washing boards | 14 November, 2011

We already have contact with Zestron and we try several chemicals and process (Immersion, aspersion, vapor degreasing). And we always find something under low standoff component. Concerning the flow pressure and shadowing, we try different position in order to improve the cleaning results but we don't see many improvement.

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#65441

Using isopropanol with DI water for rinsing after washing boards | 14 November, 2011

Have you tried an ultrasonic water cleaning process? We use an ultrasonic cleaner with tap water and Omega Aqua Clean LPH cleaner (omegasonics.com) then rinse with DI water. However, our cleaning requirements are not as strict as yours are from the sounds of it. Ultrasonic may get under components better. We are cleaning a water soluble flux.

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