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Here’s why System-in-Package is a big deal for Apple’s upcoming iWatch, and everything else

By Joe Levi April 30, 2014, 7:14 am
iWatch Concept

Pebble and other small companies are already major players in the wearables niche. Google is prepping for an imminent launch of watches powered by Android Wear. Even Samsung has its Gear lineup.

Through all this, Apple has been conspicuously absent.

We’ve suspected for some time now that Apple is getting ready to enter the smartwatch game. Now, thanks to some leaked information, we’re starting to piece together a timeline for availability, but more importantly, we could be seeing a shift away from Printed Circuit Boards to a System in Package approach.

PCBs and SoCs

Printed circuit boards (PCBs) and Systems on a Chip (SoCs) go hand-in-hand; you can’t have one without the other — not today anyway. A PCB mechanically supports various components and enables them to be connected through traces, tracks, pads, or other electrical lines. These boards can be single-sided, double-sided, or even multi-layered and connected through holes called “vias”.


PCBs can be large, small, or anywhere in between, depending on the application. The PCB in your desktop computer may measure several inches wide by several inches tall. The PCB in the Pebble smart watch significantly smaller, and even flexible to take advantage of its limited space.

What all PCBs have in common is that they allow for separate components to be interconnected on a relatively horizontal platform. These components include, but are not limited to central processor, RAM, graphics processor, cellular and other radios, sensors, LEDs, charge controllers, and screens. Each component is individually placed onto the PCB, and each is responsible for carrying out its own job.

Systems on a Chip (SoCs) are a component that attaches to a PCB. Unlike a traditional CPU, an SoC may contain a CPU, GPU, RAM, memory controller, and more, all on a single chip. This saves space, raw materials, assembly time, and cost when compared to the “individual components” model. Even still with the SoC, despite the fact that it combines numerous functions into one, still is an item that must be mounted onto a PCB — at least for the time being.

System in Package (SiP)

For computers, laptops, tablets, and even smartphones, a horizontal layout is typically ideal. In space-constrained applications, however, horizontal isn’t always better.

Take cities, for example. People who live in very rural areas may have half-a-dozen people living on several acres of land. In the suburban landscape that surrounds the Pocketnow Utah Office, a typical quarter-acre may house those same six people. In big cities, a skyscraper could house thousands of people on hundreds of floors in the same quarter acre. The difference? Build up rather than out. Such is the case with SiPs.


Unlike PCBs that, although being multi-layered, have their components arranged across a single plane, SiPs build “up”. One way to think about a device using a SiP approach is a series of small PCBs, each containing a collection of components, then stacked on top of each other, connected by wires or by solder points. In this manner, a device can be built that occupies a much smaller footprint than the same device had it been made traditionally.

When fully assembled, a complete unit can be built in a multi-chip package, requiring few external components to make the system work. Portable devices, such as solid-state MP3 players, can benefit greatly from this approach.

Despite all the benefits, building devices around this technique can decrease efficiency in production. Any defective component in the package results in a non-functional SiP, even if all other components are working properly.


If recent sources are to be trusted, Apple has already started making the iWatch — at least in small quantities. The construction method is said to be using SiPs rather than traditional PCBs.


Since these SiPs can be designed to be much more compact than their PCB counterparts, internal hardware can take up less space when compared to the other method.

Initial production runs will likely be smaller than one might expect. This could cause inventory shortages to be greater than normal for the iWatch when compared to contemporary smartphones and tablets. Should this be the case, it will undoubtedly cause some frustration in the market. The important thing to remember through all this is that making the iWatch using SiPs isn’t about the iWatch at all.

Making the iWatch with SiPs is an experiment into a fabrication methodology, getting things just right in a very small package, and learning lessons along the way. Those lessons will quickly translate into successes in other products like the iPhone and iPad, and probably even laptop and desktop computers. Sure, repairability will suffer, but costs should continue to come down, and performance should continue to increase.

The most important part of Apple’s forthcoming smartwatch may not be the watch itself. It may very well be the manner in which it’s made.


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