Ethylene Oxide cleaning of printed circuit boards

[René]

Hi All,

Has anybody experience with Ethylene Oxide cleaning of a PCB
containing SMD parts and connectors? Is a coating necessary? Will
connectors stand up (over time) after cleaning?

We are building a PCB that will be incorporated in a larger assembly
for medical application - hence the EtO cleaning...

TIA!

 

[martin griffith]

Hi All,

Has anybody experience with Ethylene Oxide cleaning of a PCB
containing SMD parts and connectors? Is a coating necessary? Will
connectors stand up (over time) after cleaning?

We are building a PCB that will be incorporated in a larger assembly
for medical application - hence the EtO cleaning...

TIA!

EtO, nice stuff....
http://www.nsc.org/library/chemical/Ethylen0.htm

martin

"An eye for an eye makes the whole world blind"
Gandhi

 

[René]

EtO, nice stuff....
http://www.nsc.org/library/chemical/Ethylen0.htm

OK - so I will not inhale.....

Anyway - we have to supply the PCB's - our customer does the dangerous
stuff. All we must do is to make the product survive the EtO.

 

[Chris Carlen]

EtO, nice stuff....
http://www.nsc.org/library/chemical/Ethylen0.htm

Yes. I came close to needing that stuff for a synthesis once, but found
an alternative approach that spared the need for this.

There is something screwy with the practice of gassing items with EtO
for medical sterilization when it has such low TLV/PELs and is a "de
minimis" carcinogen.

Something like a PCB with components would certainly retain trace
amounts of the stuff, unless baked out afterward in vacuum.

Is a vacuum bakeout part of the normal procedure for EtO sterilizations?




Good day!



--
_______________________________________________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.

 

[martin griffith]

OK - so I will not inhale.....

Isn't that what US president's claim?


martin

"An eye for an eye makes the whole world blind"
Gandhi

 

[Al]

Yes. I came close to needing that stuff for a synthesis once, but found
an alternative approach that spared the need for this.

There is something screwy with the practice of gassing items with EtO
for medical sterilization when it has such low TLV/PELs and is a "de
minimis" carcinogen.

Something like a PCB with components would certainly retain trace
amounts of the stuff, unless baked out afterward in vacuum.

Is a vacuum bakeout part of the normal procedure for EtO sterilizations?

Remember, just because it is sterile doesn't mean that it is not
contaminated.

Al

 

[Mark Jones]

Isn't that what US presidents claim?

martin

Ha! that's what all Americans claim.

 

[Joerg]

Hello René,

EtO is very corrosive. I have dealt with a lot of electronics that got
sterilized that way. There isn't much else you can do with electronics.
Radiation, for example, will destroy most of the stuff. Same with
processes that require high temperatures.

We had potted and non-potted designs. However, it was all disposable so
there were no repeat sterilization although we did have to do those to
validate margins etc.

Also, keep in mind that you will have to do other stuff as well, such as
passing the biocompatibility test. That starts with lots and lots of
paperwork. Keep in close contact to the Regulatory/QA folks of your client.

And never, never, touch anything before the outgassing phase is
completed. But people who work under a proper QA system normally won't
let you anyway.

Regards, Joerg

 

[René]

Hello René,

EtO is very corrosive. I have dealt with a lot of electronics that got
sterilized that way. There isn't much else you can do with electronics.
Radiation, for example, will destroy most of the stuff. Same with
processes that require high temperatures.

Given the fact that the PCB will be disposable and will contain fine
pitch tracks and several connectors (micromatch, slotted 1/10"
headers), what is advisable relative to coatings, connector pin
materials (gold, tin etc.)Thanks for answering!

 

[Joerg]

Hello René,

Given the fact that the PCB will be disposable and will contain fine
pitch tracks and several connectors (micromatch, slotted 1/10"
headers), what is advisable relative to coatings, connector pin
materials (gold, tin etc.)

Our circuit boards were regular issue, no fancy coatings. But with
respect to surface coating and connectors I would study a bit,
especially if you are facing multiple EtO cycles. This may be a start:

http://www.devicelink.com/mddi/archive/04/06/009.html

For connectors, gold plating is popular. But always get the
manufacturers blessing first. Here is a start:

http://www.fischerconnectors.co.uk/products/connectors.htm

Most major connector manufacturers and especially the ones catering to
the medical device industry (such as LEMO S.A.) can guide you. As I said
before, a very important aspect is that you receive sufficient data for
bio burden. Without such data a connector may be useless no matter how
good it is. Med is a heavily regulated industry, and it should be. So,
the QA folks are going to want to know what's in your design from a
chemistry point of view.

Regards, Joerg