I have cleaned several thousand uBGAs, flipchips, and BGAs using this method, except I do not use alcohol. I use a 13:1 mix of 13 parts deionized water to 1 part saponifier (heated to about 140 deg F). This will prevent the reaction that causes the white residue. If you clean them in plain deionized water, tap water, or alcohol, the reaction occurs. After the wash in the US with the 13:1 mix, I follow that with a rinse in hot deionized water to remove all saponifier residue. I have never had a BGA or any other component fail after cleaning with this method. But I could have been lucky. Usually the wirebonds at this stage are captured in epoxy, so there should be little danger of damage. Perhaps you could try cleaning 5, assemble them and get them through test, then try 10 and repeat the procedure, then if there are no failures at this point do the balance of the lot. This is a controlled procedure that is a good indicator that the parts are not being hurt by the process.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Saturday, August 13, 2005 2:24 AM
To: [log in to unmask]
Subject: Re: [TN] Ultrasonic Cleaning
Damage may occur in a few milliseconds. It depends on at least 10 factors, some of which are imponderable, such as where the nuclei are that trigger the cavitation.
Brian
David Tremmel wrote:
> Dear forum,
>
> I have some microBGAs which have a no-clean flux residue which must be
> removed before they can be reballed.
>
> I have been doing my homework regarding USC (ultrasonic cleaning) and
> would like opinions on whether or not putting the microBGAs in alcohol
> and putting them through a US cleaning cycle for 1 minute would damage
> the wirebonding.
>
> Most of what I see regarding USC is negative, but would only a minute
> be damaging to the parts or does the damage occur after more time
> (i.e. - 3 minutes, 5 minutes).
>
> As always, I appreciate the feedback.
>
>
> David
>
> P.S. - Ramon, you said a 15 minute soak in alcohol would do trick, right?
>
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