Hi Constantino,
On basic principles, the connection shown in 'image003' is a good idea. Because of 'pad cratering', which comes from the combination of the much stiffer SAC-solders with BGA warpage, trace fractures can result.
The first thing to reduce pad cratering is to slow down cooling after reflow to no more than 1.5C/sec; the second is to use higher-Tg/lower alpha-2 resin for your PCB; the third is 'image003'. But as long as you have pad cratering, even 'image003' may not totally prevent trace fractures.
I show all of this in my workshop---see below.
Werner
Future workshops:
Pb-Free Soldering Processes-Survival, Quality, Reliability, March 5, Santa Clara, CA
Solder Joint Reliability: Part 1--Fundamentals, March 29, Las Vegas, NV
Pb-Free Soldering Processes-Survival, Quality, Reliability, March 30, Las Vegas, NV
-----Original Message-----
From: Constantino Gonzalez <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, 22 Dec 2008 10:04 pm
Subject: [IPC-600-6012] Pad to trace interface on BGAs.
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 tha
t 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.
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