James-
As a relatively new user and designer of PBGA, here's an off the top of
my head list of issues:
1. Eutectic solder joint reliability, especially under conditions of
high-shock and extreme temperature dormant storage for military
applications: How can we better model and analyze the solder array? How
can we create accurate predictions of fatigue life, using a better
understanding of the evolution of alloy microstructure, as it affects
joint lifetime (see Darrell Frear, of Sandia Labs, papers over the last
10 years). When is underfilling required for extreme environment
applications for PBGAs?
2. For thin, 2-layer PBGA substrates, a better understanding of
compromised solder joint reliability, where balls are located on the
opposite side of the substrate, near the edge of the die. At what point
will thicker, stiffer substrates, and "compliant" die atttach joints or
materials, be able to mitigate this problem?
3. Improved moisture resistance (JEDEC level 2 or 1) for PBGA: what
improvements in PBGA organic substrates, die attach materials, and die
encapsulant/overmolding are required?
4. For Au wire bonded PBGAs: a better understanding of "gold
embrittlement" issues, when eutectic solder balls are attached to Au
over Ni substrate platings. How does the intermetallic layer evolve and
grow with time and exposure to elevated temperatures? What Au plating
thicknesses, or percent Au in solder joint levels, will lead to solder
joint reliability problems?
5. PBGA solder ball coplanarity control, for more producable assemblies
using PBGA components. What complanarities are required as a function of
pre-attachment ball height?
6. PBGA will probably dominate over ceramic. The use of PWB-based
substrates and eutectic PbSn will continue to make PBGA the more
attractive and lower cost option.
-Michael Alderete
> ----------
You wrote...
> ------------------------------
>
> Date: Wed, 16 Sep 1998 08:30:40 -0500
> From: "Michaud, James (STP)" <[log in to unmask]>
> Subject: Re: X-ray for open joints on BGA's ?
>
> Marcelo -
>
> Hello. I am a Reliability Engineer working for a Medical
> Electronics
> company. We're currently reviewing BGA reliability. We'll be producing
> equipment for hospital Emergency Rooms.
>
> I've noticed the discussion on BGAs you've been involved in.
> I'm concerned about BGA reliability issues. You mentioned
> "there is
> a lot that the industry still do not know about reliability." In your
> opinion,
> what are the most critical BGA reliability issues? Our guys
> think
> plastics are better than ceramics. What do you think?
>
> James Michaud
> Guidant-CRM/CPI
> Dept. 5512, MS F240
> 4100 Hamline Ave. N.
> St. Paul, MN 55112-5798
> (612) 582-7842
>
>
>
>
>
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