Device Embedding and Stacking Point to Packaging?s Future
Alexander E. Braun, Senior Editor?Semiconductor International, 11/16/2007 
In the packaging sector of the semiconductor industry, the most 
significant current trend is device embedding and stacking. Devices today 
are being stacked in ways that would have been inconceivable just a few 
years ago. This is taking place in different packaging configurations, 
silicon on silicon, and by embedding. ?Device embedding is increasing,? 
said Steve Adamson, IMAPS president elect, at the recent IMAPS 40th 
International Symposium on Microelectronics, held in San Jose this week. 
Adamson added that it is becoming common to see many passive, as well as 
active, devices going inside the circuit board.
In 1999, Motorola was one of the first in the industry to begin putting 
passive devices in the circuit board for cell phone applications. Cell 
phones have certainly evolved since then, when the user had to first pull 
out an antenna before making a call. Now cell phones feature TV, Wi-Fi, 
Bluetooth, GPS and other options, all requiring different antennas. In 
some cases, there may be as many as 15 different antennas in a small 
package. Development in this area is expected to continue, particularly as 
further advances take place in the signal-processing arena.
Adamson believes that the traditional distinction between a circuit board 
and package is beginning to blur, becoming, as he put it, ?a moot 
question.? The driver behind this integration and move to embed originates 
from increasing efforts, particularly in the area of consumer electronics, 
to offer the best functionality and most features at the lowest possible 
price-to-cost ratio. Consumers want cheaper gadgets that are smaller and 
do more, and the demand is energizing packaging technology to meet these 
requirements. ?In a survey done in Japan,? Adamson said, ?everyone queried 
said that by 2012, cameras, PDAs, iPods, phones - everything - will be 
embedded. This means that the whole 3-D space will be used.? Although 3-D 
can be considered as being in its infancy and there is still much to 
learn, Adamson is concerned over the lack of the needed development 
capabilities. ?People have to use multiple software tools to lay out PCBs 
and design these packages,? he said. ?There still is no true 3-D layout, 
EDA-type package today.?
Because there are so many approaches, seemingly with new ones being added 
each day, the embedded arena - whether dealing with passive or active 
devices, a film or a layer - is in a state of flux. However, some 
traditional approaches, much like the Old West town of Tombstone, seem too 
tough to die. ?I am always extremely surprised by the wire bonding 
providers and how they always come through,? Adamson said. ?They?re doing 
things today with wire bond we would have never even dreamt of 20 years 
ago. Everybody talks about the end of wire bonding, how we?re going to tab 
bonds or beam leads. Well, perhaps, but I?m never going to bet against the 
wire bonding guys.?
Although device stacking and embedding is definitely the direction the 
technology is taking, nevertheless, things like flip-chip are still being 
done, demonstrating that there are different uses for different 
application points. ?For IMAPS to be at the leading-edge, we must also 
look at other work being done, such as that being carried out to remove 
heat from other devices such as LEDs,? Adamson said. He thinks that they 
should also track some of the more exotic things - biochips, for example. 
As he put it, ?It has a chip, a wire bond, a cover on it, and a piece of 
silicon, and it looks to me like one of our core technologies. The fact 
that you may put a trace of blood or something else on it makes it 
somewhat different, but it still has to be connected to the outside 
world.?