IPC T-50, Revision H, Terms and Definitions for Interconnecting and Packaging Electronic Circuits, has addressed this term.
Pad Cratering 96.2176
A separation of the pad from the printed board resin/weave composite or within the composite immediately adjacent to the pad as a result of mechanical and/or thermal stress.
Mike Green
Electronic Packaging Design
LMCO-Sunnyvale
408-743-1635
One Corporation, One Team
"Those who have nothing to follow must lead." M. Green, 2008
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Tuesday, December 30, 2008 8:53 AM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Pad to trace interface on BGAs.
Tino,
Cratering is your culprit, and as pretty common. You shouldn't have much trouble finding help. Werner would top my list of the non-free variety. IPC-7095B is an excellent source of general info.
Without changing the design, "better" laminate material and cool-down will probably fix you up.
However, I'll bet you a nickel that this is a foil laminated board and that if you tested peel strength (after assembly reflow excursions) it would be 0.5 to 0.7N/mm (much lower than it should be). In other words, the board fabricator might bear some responsibility. We find peel strength to be an good, cheap tool for monitoring adhesion/cohesion degradation at the surface. The military still requires peel testing as periodic conformance (albeit, not after convection reflow, or at elevated temp). 6012 voted against it.
BTW, does anyone have an action to take "cratering" to T-50?
Happy New Year to all.
Chris
Chris Mahanna
Robisan Laboratory Inc.
6502 E 21st Street
Indianapolis, Indiana 46219
317.353.6249
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Constantino Gonzalez
Sent: Monday, December 22, 2008 10:04 PM
To: [log in to unmask]
Subject: [IPC-600-6012] Pad to trace interface on BGAs.
Importance: High
Hello, I have a customer with a problem described below, Could you PLEASE HELP ME?
The problem is that several boards are being returned to the plant after failing in the field.
After Failure Analysis the engineers have found that the reason for the failure is that one of the traces of the PCB connected to a BGA pad is becoming cracked (Micro crack at BGA Pad AJ29 in the corner of the BGA) as showed in picture below:
image001.gif image002.gif
They have concluded that Copper qty at PCB layer is not enough to support the normal Mechanical Stress in the unit chassis during the Transportation resulting in the trace and pad crack.
Based on Jedec JESD22B113 standard, they are suggesting that the customer change design on the traces connected to BGA pads as shown below: Does the
IPC7351 suggest anything related to this...
image003.gif
I have not heard before about this type of junction from traces to pads, and being honest I did not know the Jedec STD mentioned.
Have any of you ever heard about this special union from traces to BGA pads to avoid stress or any other recommendation to reinforce trace to pad joints?
Could you please enlight me with your thoughts or opinions about this issue?
Regards.
Constantino J. González, ACME, INC. - GALUSAMEX REPAIR Co.
President / Consultant Engineer - Official IPC MASTER INSTRUCTOR - IPC-A-610 Committee Chairman USA Cell Phone: 605-381-5963 - Mexico Cell Phone: 55-2709 - 6392 - <mailto:[log in to unmask]> [log in to unmask] or <mailto:[log in to unmask]> [log in to unmask]
Does your Company need Rework, Repair or Inspection of Electronic Assemblies Services.
Do you have too much Rework, Scrap or Rejects from your Customer.....Call us, We can help!
GALUSAMEX REPAIR Co.
|
