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After PCB CLEANING with acqueous , drying needs?

P.GERARDIN

#3113

After PCB CLEANING with acqueous , drying needs? | 5 September, 2000

We intend to promote the new PCB cleaning process with acqueous chemistry , but we face with an important demand :

Do we have to dry the pcb after ?

Wich is the treshold humidity content to avoid any risk for FR4 material ?

Regards

Pascal

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Chris May

#3114

Re: After PCB CLEANING with acqueous , drying needs? | 5 September, 2000

Pascal,

Hopefully, the system that you invest in will have a programmable drying cycle as one of its features.

As far as humidity content is concerned, I am sure that some more learned colleagues may be able to help you.

Although, I believe some people still "bake" bare boards, and some don't. Hopefully the people that bake and then aqueous wash have a system with a dry cycle. otherwise why get rid of the moisture and then reintroduce it?

Regards,

Chris.

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#3115

Re: After PCB CLEANING with acqueous , drying needs? | 5 September, 2000

Pascal: Responding to your questions:

1 Do we have to dry the PCB after cleaning (sic)?

Generally, nothing says you have dry the PCB after aqueous cleaning. Along this line, I received several thoughtful responses when I posted a similar thread. Look at:

Why Dry After DI? - Dave F 18:52:10 07/06/1998

Continuing, J-STD-001 states that boards must meet an established cleanliness requirement. It requires neither cleaning nor drying after cleaning. So, the method you use to meet the cleanliness requirement of the product shipped to your customer is up to you.

2 Which is the threshold humidity content to avoid any risk for FR4 material ?

Short [but not particularly useful] answer: It depends on how your process the board and on the design of the board.

The time of greatest risk posed to FR-4 boards by humidity content is during soldering cycles, as Chris mentioned earlier, because FR-4 is hydroscopic [ it wants to take-on moisture].

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