Insights From Leading Edge

IFTLE 185 Lecturing the Packaging Community on Nomenclature

The word “lecture” is one of those wonderful English words with multiple meanings. Lecture can mean “a talk or speech given to a group of people to teach them about a particular subject,” but it can also mean “a talk that criticizes someone’s behavior in an angry or serious way.” In IFTLE 185, lecturing means both!

Those of you that are regular followers of IFTLE know that every once-in-awhile, I’ll stop reviewing the latest technology presentations to try to bring home a point. The latter is necessary right now.

Some may call this one of my “rants” but the online dictionary defines a rant as “…an argument fueled by passion and not shaped by facts.”  I can assure you this rant will be shaped by both passion and facts.

What triggered IFTLE 185 was a panel session held at the recent IMAPS Device Packaging Conference in Ft McDowell AZ. A good panel session experts discuss controversial topics but that is not exactly what happened here.  This panel session degraded into a school yard verbal battle (panel members and audience) over what certain terms mean. If you really want to follow the chronology of the discussion you can here [Advanced Packaging Alphabet Soup Creates Chaos for IMAPS 3D Panel].

It is simply amazing that the assembled group of technical practitioners could not agree on what certain packaging terms mean but….they couldn’t. At first I chose to sit quietly in the audience amused at the miss speak…but then… my good friend Bob Patti, a panel member,  spotted me in the corner of the room and called me out …” Phil what do you think “…it was at that point , no longer able to hold back, that I unleashed my tirade […a long angry speech of scorn and criticism…]

Let me attempt to articulate my position on several of the topics that came up that night …

INTERPOSER – for some reason, be it ignorance, youth or a combination of both, some in the audience continue to believe that the term interposer was invented for 2.5D.

All 1st level packages are interposers, The purpose of an interposer is to spread a connection to a wider pitch. Interposer comes from the Latin, interpĹŤnere, meaning “to put up between.” A BGA substrate is an interposer ! This is clearly shown in the Infineon slide that they have been showing for nearly 20 years.

infineon 2

SYSTEM-in-PACKAGE – there was mass confusion on what this meant and what is included in this definition. Several experts felt that 2.5/3D were NOT included in the definition of SiP. I think some of these disagreements come from the fact that corporations do not divide things up in their business units based on definitions so all things SiP may not be in the same business unit and this influences their thinking.

In the 1990s multiple chip packages, MCMs as they became known, were sets of chips that were connected on high density Si, laminate or ceramic substrates by WB or C4. In the early 2000’s it became vogue to call these system-in-package as industry focus became delivering functions for portable devices in separate modules. Need more history on MCMs try the Multichip Module Technology Handbook [link] which Iwona Turlik and I edited in 1998.

Let’s look at another Infineon slide, below. Whether its side by side, stacked, through hole or embedded, these multiple chip solutions are all versions or categories of SiP.

Infineon 1

2.5D, 2.1D and 5.5D: Please stop the madness!

3D packaging defines the various ways of stacking chips in the z direction whether it be WB them to a common substrate, package-on-package stacking, embedded chip stacking (in laminate or EMC ) or direct connection with TSV.

The term 2.5D is usually credited to ASE’s Ho Ming Tong who ~ 2009 (or even earlier)  declared  that we might need an intermediate step towards 3DIC since the infrastructure and standards were not ready for 3DIC stacking yet.  Tong felt the silicon interposer would get us a major part of the way there, and could be ready sooner than 3DIC technology.  He used the term 2.5D, which immediately caught on with other practitioners. Tong was not trying to create a new nomenclature, he was making a joke that we were not ready for 3D but this silicon interposer with TSV would get us close. He actually got laughs when he called it 2.5D at the RTI ASIP conference fall of 2009.

We are now starting to hear the laminate community use the term 2.1D for high density laminate and some in the silicon interposer community using the term 5.5D  for a 3D memory stack on an interposer. To all this, all I can say is “STOP – Enough-is- enough…it’s no longer funny..”

At one point during Bryan Black’s AMD talk at the conference he said “3D” and the audience interrupted him to ask whether he meant 2.5D. His response was something like “Oh yeah…well they both mean the same thing to me..” meaning we are talking about stacking technology with TSV.  Bryan is correct!


LAP is being held out as the solution to everything that is not economical these days. FOWLP not low enough cost to break into commodity applications ? …don’t worry we’ll use LAP and the price will come down. Glass interposers not looking like the price will be low enough for mobile products?…don’t worry we can manufacture on LAP lines and the price will come way down.

Certainly our microelectronics educations have taught us that larger usually means cheaper, i.e. chips from 300mm lines ARE cheaper than the same chips from 200mm lines. This is true as long as the equipment and technology is available to give you high yields, i.e. see the current 450mm situation.

My point to the audience was that PCB are made in large panels because they can be…higher density BGA substrates are made in much smaller strips because they have to be!

I actually have hands on experience at what we called LAP back in 1995-1997, as we had a major DARPA contract to try to manufacture MCM substrates  on a sq 400mm format. Check out my chapter “High Density, Large Area Processing (LAP) in the Multichip Module Technology Handbook [link]. By the way our program with MMS and others to manufacture high density MCM substrates made for a great magazine cover (see below)…too bad it didn’t yield!


Do I think that pursuing high density LAP is a worthy R and D goal ?…certainly, lets just not act like it will be easily accomplished.

Other problems with today’s nomenclature?? Let me know …

For all the latest in 3DIC and other advanced packaging, stay linked to IFTLE !



Easily post a comment below using your Linkedin, Twitter, Google or Facebook account. Comments won’t automatically be posted to your social media accounts unless you select to share.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>