Packaging and Power

Parasitics Everywhere

When you mention a product’s “power consumption,” packaging is not normally the first thing that comes to mind. Usually you’ll conjure up images of battery life or the heat dissipation or the extreme capability of the product. However, packaging plays a key role in a product’s power consumption rate. For this discussion, we will talk about the packaging of multiple components to create a product, such as a mobile phone.

Traditional mobile phones have three main components: a power management IC (PMIC), a baseband modem (BB) and one or more RF transceivers. Information is transferred between these components by signals that flow from one component to another on a printed circuit board (PCB). The PCB has parasitic, or unwanted, capacitances and impedances that the output circuits must drive. If the output circuits are not capable of putting out enough power, the signals between components can be corrupted, which can cause a system failure, such as a dropped call.

The larger the distance between two components, the more parasitic capacitance and impedance the output circuits must drive. So, to reduce the output circuits’ power consumption, the components should be placed as close to one another as possible. This has the additional benefit of making the product smaller. If taken to the extreme, the components can be placed so close that the packages touch one another. The next step is to merge the packages and put both die into the same package. Taking one step further, the two die within a package can be moved closer to each other until they touch, with the final step being both die integrated together onto a single die. Some companies are doing exactly this in the mobile phone arena with their “single chip radios.”

Single Chip vs. Single Package

The one major drawback of single chip radios is that the integration of the various components introduces compromises in the circuit designs, which can lead to less efficient designs that may consume more power. Integrating all components into a single chip also has the unwanted side-affect of making the product inflexible to change.

Freescale is pioneering a new packaging concept called redistributed chip-scale packaging, or RCP. RCP moves the die as close together as practical while still allowing each component to be fabricated in the process that is best optimized for its functionality. For instance, high power circuits like those found on PMICs can be fabricated in a SmartMOS(tm) process that is tailored to source high power. Other examples are fully digital baseband modems and application processors that can take advantage of the smallest geometry processes to make them as small as possible.

RCP not only allows for each function to be fabricated in the most optimum process, but also it allows the flexibility to mix and match components to meet the quickly changing demands of the consumer marketplace. With product lifecycles dropping to less than a year in some instances, this flexibility is very important for new product developers to stay competitive.

Selecting components in the right packages is important to your end product it affects not only the size of your product but also the power consumed.

– Chris