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Cleaning for conformal coat

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#68014

Cleaning for conformal coat | 25 January, 2013

I'm using urethane conformal coat and have fisheyes and dewetting after coating even though the PWAs have been through the wash cycle twice. I'm looking at using Ionox 13302 in an ultrasonic cleaner as a short term solution until root cause can be identified and resolved. What are the pros and cons of this solvent? Is there a chance of component damage as there are sone potentiometers on boaard? Will the labels, inspection stamp impressions, or other markings be removed? What temp does the rinse water have to be and for how long?

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#68015

Cleaning for conformal coat | 25 January, 2013

I'm using urethane conformal coat and have fisheyes and dewetting after coating even though the PWAs have been through the wash cycle twice. I'm looking at using Ionox 13302 in an ultrasonic cleaner as a short term solution until root cause can be identified and resolved. What are the pros and cons of this solvent? Is there a chance of component damage as there are sone potentiometers on boaard? Will the labels, inspection stamp impressions, or other markings be removed? What temp does the rinse water have to be and for how long?

reply »

#68016

Cleaning for conformal coat | 25 January, 2013

By "they've been through the wash cycle twice" what do you mean? What kind of cleaning process do you use? What sort of chemistry? How do you handle the assemblies after wash and before coating? Do the operators where power free gloves?

-Phil

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#68017

Cleaning for conformal coat | 25 January, 2013

Thank you for replying Phil. We use water only wash at 130°F and at 4 ft/min (about 2 min). They are mostly dried by the hot ait knife and left to air dry until next day. The operators do not wear gloves. When I run a bare board through the same process as the populated boards, handled by the same operstors, I have no problem. Nothing can be seen on the boards under black light. I want to try Ionox 13302 for short term but don't want to risk damaging the potentiometers.

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#68019

Cleaning for conformal coat | 25 January, 2013

You definitely have to be careful with unsealed components and markings/labels. The best you can do is check with datasheets or find an extra assembly to test it out on first.

You can also try slowing down your inline to more like 1-2 ft/min and see if it has any effect. I'm guessing you run a water soluble process?

-Phil

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#68021

Cleaning for conformal coat | 25 January, 2013

Water soluble process, yes. The machine is old and fixed at 4 ft/min by someone way before me. Looking into ways to reverse that to allow for adjusting the conveyor. Trying to determine how the contamination gets onto the boards. So far testing has indicated that the process is not adding any contaminates, but may not be removing them.

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#68026

Cleaning for conformal coat | 28 January, 2013

John, In addtion to the cleaning process you may wnat to look at the masking materials you are using as well.

Are you using any temporary masking tape? If so, do the dewetted areas coincide? Some of these tapes use a silicone-based adhesive which will cause dewetting if not properly cleaned off.

What type of urethane coating are you specifically using?

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#68030

Cleaning for conformal coat | 28 January, 2013

Good morning Mark,

No issues around the masking at this point. The issue seem to be in open areas as well as between clad runs.

We are using Humiseal 1A33 Conformal Coat.

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