Very small connections will provide sufficient connectivity to pass
electrical continuity testing.  I would make sure that the testing
parameters are correct - at least 100VDC, with a threshold of 10 OHM to
10 MEGOHMs for continuity and isolation.  One important element in this
is the microsection testing program.  Barrel cracking is generally a
ductility issue with the plating deposit, which could be aggravated by
excessive thermal excursions, substandard construction/base laminates.
Implementing a comprehensive microsection analysis program will prevent
this issue from being delivered to the field.  This is a current
requirement of both MIL and Commercial standards and you supplier should
be able to provide evidence of this program to you on request.          


Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com	



-----Original Message-----
From: Sherif Refaat [mailto:[log in to unmask]] 
Sent: Friday, June 11, 2004 11:20 AM
To: [log in to unmask]
Subject: [TN] Electrical Test capabilities
Importance: High


Hi Technetter,

I've got some questions regarding bare boards Electrical testers
capabilities.

1) Is it correct that bare boards electrical testers may not detect
opens caused by complete copper cracks (circomfrential) inside via holes
because the pressure from the test pins do close the crack? ( I
personally do not think so. The copper crack width measured from the
cross section is 0.0004"). The boards I'm talking about are Immersion
Silver plated.

2) How about via copper cracks if the boards are HASLed. Would the
Tin/lead inside the via holes allow enough conductivity to "hide" the
copper crack?

3) If the copper plating thickness inside the hole is considerably
reduced (for example, down to 0.0004" from 0.001") would that be
detected by the E-tester as high resistance?

4) How the test parameters affect the above issues?

Your response is greatly appreciated.

Have a good weekend.



Sherif Refaat, Eng.





 





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