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ESD Compliant - Air blow off to dry washed circuit board assemblies

Ashok Dhawan


ESD Compliant - Air blow off to dry washed circuit board assemblies | 11 April, 2000

I am looking for an appropriate method to dry wave soldered boards. While board assemblies are passed through board cleaning station , they are not fully dry . We do not want to heat above 180 deg F to dry them completely. We think that air drying using a compressed air gun could help us ? But this may create static charges which might damage the circuit board assemblies ? Should we use air ioniser in drying area or use special ESD Compliant gun ? Can anyone advise me what is reasonable process ?

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Re: ESD Compliant - Air blow off to dry washed circuit board assemblies | 11 April, 2000

Ashok: You're still goin' down that ol' ESD road aren't ya bud?

Why do you need the boards to be dry? Conformal coating? Hey wait a minute, are you one of those no-clean people? Er zis related to the Kapton tape res fandango?

Anywho, be careful with compressed air. It needs: * Pressure regulation, so not to hurt someone with flying debris. * Filtration, so not to coat the boards with oil and water. * Evaluation of a need for ESD control, so not to damage components from the friction of the air moving by them.

Our ol' friend Jack asked a similar process drying question a while ago. Check:

convection batch ovens - Jacqueline Coia 05:09:18 12/02/1998

Good luck Dave F

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Re: ESD Compliant - Air blow off to dry washed circuit board assemblies | 12 April, 2000

Ashok: You still didn�t tell me why you want additional drying of your boards, but what the hey, we all have our dark secrets.

Anywho, let�s consider some options for reducing the moisture of your cleaned boards:

OPTION 1 - Up-Grading Your Cleaner: Consider adding a module with an additional air knife, an IR heater, or both to your cleaner. Most cleaner suppliers can field up-grade their cleaners. They�ll be able to weld that onto you existing machine fairly easily. (If the person buying your cleaner was shrewd, she bought it with the extra space and now all you have to do is install the gear. But then again, we all know how that goes.)

Anyway, this may be the way to go, given that: � Removing the mist or wetness thing is not short term need. � You�re not inclined towards either: - Slowing down the conveyor speed � OR - Increasing the drying temperature. � You�re not going to get the boards dry with an air gun (my opinion).

This will give you dry boards, lower your labor content, and may even allow you to up your conveyor speed, depending on whether cleanliness or dryness is limiting your cleaner through-put.

Ou, ou, (as Guther Tooty used to say) suddenly, it dawns on me as I write this, the folks on your RMA flux line have thought through this already and decided against it, which is why they�ve dragged you (the ESD Prime) into the project, because the decision is made ... ve vil go vit Option 2 und ve vil like it!!!

OPTION 2 - Using An Ionizer-Gun: (which you seem to really like, orzit you have no choice? Yes, you have no choice.) (which on one hand, I have to agree, sounds like a nice, low capital cost approach. But on the other hand, it also sounds like a high labor cost, low process quality control approach and worse yet probably will not dry the boards.)

Anyhow, since you have good compressed air supply that�s clean, moisture free, and well regulated and you�ve handled all the personal safety and Canadian occupational health & safety issues, two questions remain:

1 Will this do more bad than good to the circuit boards? Real question of product safety falls on the broad shoulders of the ESD Prime, you!!! � First, it�s the obligation of your ionizer gun supplier(s) to demonstrate that their product poses no potential damage to your product. � Second, it�s your obligation, as ESD Prime, to foist all responsibility for this onto the ESD Alternate. No, no, that�s not the way it�s sposed to work!!! You need to set-up a monitoring process similar to the monitoring processes that you use for your ESD wrist and heel straps, floors, ionizers, etc. 2 How dry do you need the boards and will this approach work? � If you need dry boards because you�re going directly to ICT or coating, I cereally doubt a little spritz with cold air is going to accomplish much. � If you just want to remove the BIG puddles of water from the board, it�ll be fine, but then again having someone run around the room waving the board over their head will do that also.

Lemme breakdown the remark about high labor cost, low process quality control approach. High Labor Cost: I picture a money standing at the end of the cleaner with an ionizer gun spraying-down each board as the exit the machine, which seems like a real labor and throughput sink hole. Low Process Quality Control: It will be difficult to determine when a board is dry. For example, boards with connectors are wetter than those without.

OPTION 3 - Baking The Boards In A Oven: Buying a used Blue M baking oven (from LR or whoever) may be the best solution from both a capital conservation, low labor cost, and reaching board dryness standpoints.

Good luck Dave F

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