TECHNET Archives

November 1999

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Michael Forrester <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 11 Nov 1999 12:29:12 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (40 lines)
We are currently seeing strange component failures in the PLL circuit of one of
our assemblies.  The components are as follows:

     1) BB619 Tuning diode SOD-23, defective
     2) 1500 pF NPO Nickel Barr .080 X .05 Cap, becomes resistive?
     3) BAV99 Dual Diode SOT-23, PN junction damaged

     All of the parts are surface mount an contained within the walls of a SMT
RF shield with just the fence installed during reflow.  The dimensions of the
fence is 1.75" square at a height of .5".  We use a very similar circuit on
another assembly that does not have any of these problems nor does it have a SMT
RF shield.  I believe the damage to the components is heat related?  One theory
I have is during reflow, the shield fence acts as a large heat conductor and
transfers the heat , through the ground, to the components causing heat related
damage?  All but the tuning diode has one pin connected to ground.  I have never
heard of a case where something like this has happened.  Could it be heat
radiated off the four walls of the fence, creating a oven within the area of the
walls?  Does anyone have any other ideas or have seen similar problems?  Any
help would be appreciated!  Thank you.

Best Regards,

Mike Forrester
LeCroy Corp.
[log in to unmask]

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################

ATOM RSS1 RSS2