Hi Bev,
I had the same issue on a board about two months ago. It was on a 44 pin
QSOP. Leads on one side were about .010" above the pads.
Bev Christian <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/21/2005 10:59 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Bev Christian <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] Moisture sensitivity levels...
In the past I've seen a TSOP popcorn so bad that the bottom was "pregnant"
enough that the leads on one side were about 20 degrees off the board.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey
Sent: June 21, 2005 10:44 AM
To: [log in to unmask]
Subject: Re: [TN] Moisture sensitivity levels...
No, you are all wet. The sudden vaporization of moisture in plastic or
epoxy
can pop the die off the carrier, pull wire bonds off the die, crack the
package and expose internal workings of the device, and more. Popcorning
is
a good name. Recently, I saw a device just like the one you describe. A
ceramic with gold wire bonds, cavity filled with epoxy as an encapsulate.
The epoxy absorbed water which erupted during reflow and created a large
void in which the bond wires bent and made unwanted electrical contact. .
.
with very weird symptoms.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Dehoyos, Ramon
Sent: Tuesday, June 21, 2005 9:27 AM
To: [log in to unmask]
Subject: Re: [TN] Moisture sensitivity levels...
I may be totally wet but my assumption has been that there needs
to
be a cavity such as in the QFPs or DIPs for enough moisture to create
enough
pressure to pop a device. Based on this assumption, perhaps if the
cavities
were potted after wire bonded there would not be a need for MSL nor the
prohibition against ultrasonic cleaning. I have seen some components with
a
jelly like material inside over the electronic device.............. Just a
thought.
Ramon
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