immersion clean: you mean it specified as in-line water clean with  
top spray type?  the contact time for the venting hole possibly is  
much less time and not much chemical attack on its sealing epoxy  
(most likely, acrylic type... although it called epoxy - Few good UV  
curable true epoxy =chemically speaking, electronic grade out  
there... you need short wavelength UV cure = lamp is more expansive  
than your standard 365 nm curing lamp).  if you use dish washing  
machine, possibly with some chemical additive as agent, it might  
weaken the "epoxy".  the contact time, and chemical may not be  
compatible to your parts.  Just wondering, you should be able to pull  
out of the qualification of those parts and review the process  
evaluation and see if any reliability test being done = so much  
water, with large population of parts exhibit water ingress, you got  
see some performance indicator when you qual... unless someone skip  
the whole parts qual process.  (proper cured UV epoxy top surface is  
heavily oxidized - if it is true epoxy, it should be hydrophobic,  
short time in contact to a spray water of DI followed by air knife  
and drying process should not be a problem in the cleaning process,  
if the design intent is for in-line immersion clean).
my 2 cents.
            joyce
On Mar 19, 2015, at 4:46 PM, Carl VanWormer wrote:

> Here is the second of two stories about relay failures caused by  
> our assembly process:
>
> We have another product with mostly surface mount parts, along with  
> one through-hole relay and some 48-pin through-hole connectors.   
> After the SMT parts are reflowed, the boards go through a wave  
> soldering operation to attach the four connectors and the relay.   
> Our first batch of 50 boards had 6 fallouts that were traced to  
> "bad" relays.  Since I had recently been burned by water in  
> "sealed" relays (another style, from another manufacturer), my  
> paranoia kicked into high gear.
>
> The datasheet shows these relays as "Fully sealed", with a note to  
> "Contact your OMRON representative for the ratings on fully sealed  
> models."  Searching the relay manufacturer's website turned up a  
> few more documents.  One document, titled Electromechanical Relays  
> Technical Information shows that for Fully Sealed relays:
> Boiling cleaning and immersion cleaning are possible. Ultrasonic  
> cleaning will have an adverse effect on the performance of relays  
> not specifically manufactured for ultrasonic cleaning. The washing  
> temperature is 40°C max.
>
> My guess is that our wash process (and probably yours, too) is  
> above 40°C.  This is probably how I screwed this one up . . .
>
> Opening up the 6 failed relays showed significant water inside.   
> Since these boards were produced last month, they had been sitting  
> on the shelf for several weeks, with the water and other chemicals  
> causing problems, including mechanical binding.  My real fear was  
> that other boards that tested "good" might have water inside and  
> would soon go bad.  The failed boards showed several different  
> problems, but a common feature attracted my attention.  During the  
> initial board testing, as I ramped up the DC power supply (that  
> activated the 24V rated relay coil), all of the good boards made a  
> little "tick" sound as the relay armature took up slack in the  
> system, but didn't have enough force to overcome the return-spring  
> force.  This sound occurred at about 8V, except for the "bad"  
> boards.  I touched a 9V battery to the coil drive pins while  
> holding a bad relay against my ear.  I could only hear a slight  
> "tick" sound.  Holding a good (new, never been washed) relay up to  
> my ear, then touching the battery to the pins gave a louder,  
> stronger "tick" that had a little ringing character that was not  
> present in the bad relays.  The difference was subtle, but similar  
> to the difference in sound from dropping an old (Copper) penny and  
> a new (Zinc) penny.  I cut the top from a good relay, listened to  
> the sound as I touched the coil terminals to a 9V battery  
> (reference, good).  I ran water over the exposed (good) relay, and  
> shook off the excess.   Activating the dampened "good" relay gave a  
> sound that was more muffled, lacking the "ring" of the little  
> vibrating parts as the water film damped the vibrations.  With this  
> test, I was able to check all of the "good" boards, finding that  
> they all had the "ring" of goodness (hopefully with no significant  
> internal water).
>
> I'll send some pictures to Steve for his wonderful picture hosting  
> service.
>
> Once again, our planned solution to the problem is to add the  
> relays after the final board cleaning, using a no-clean flux solder.
>
>
> Once again, our conclusion is: don't wash relays, regardless of the  
> datasheet information.
>
>
>
> Later,
>
> Carl
>
>
>
> p.s.  there will be no follow-up water-in-relay stories from me  
> because I'll never allow a relay to run through a wash system. This  
> goes for potentiometers, too, since I've had "sealed" pots fail  
> after washing.
>
>
>
>
>
> Carl B. Van Wormer, P.E., AE7GD
> Senior Hardware Engineer
> Cipher Engineering LLC
>     21195 NW Evergreen Pkwy Ste 209
>     Hillsboro, OR  97124-7167
>     503-617-7447x303
>      
> [log in to unmask]<mailto:[log in to unmask]>      
> http://cipherengineering.com<http://cipherengineering.com/>
>
> This message may contain confidential and/or proprietary  
> information, and is intended for the person/entity to whom it was  
> originally addressed. Any use by others is strictly prohibited.  If  
> I sent this to you by mistake, please be nice and delete it, and  
> then tell me of my mistake so I can send it to the right person.
>
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud  
> service.
> For more information please contact helpdesk at x2960 or  
> [log in to unmask]
> ______________________________________________________________________

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________