With the wearable and Internet of Things (IoT) markets exploding, chipmakers are packing more electronics in smaller pieces of silicon to create such products as system on a chip or SoC integrating microprocessors and associated circuitry on a single silicon chip.
Active devices like SoCs and passive devices are now produced in increasing smaller packaging such as micro ball-grid arrays (BGAs), chip scale package (CSP), and quad flat no-lead (QFN) packages.
Fig. 1 shows micro BGA-packaged devices placed on a flex board for a wearable medical electronics application. These tiny micro BGAs can house such complex circuitry as powerful processor chips or a system-on- a chip (SoC), for example.
To learn more about wearable PCBs and the keys to successful assembly and manufacturing read our article in Assembly Magazine.
Meanwhile, it’s good for wearable/IoT OEMs to know that conventional small component packages such as 0201 and 01005 are among today’s packages causing major PCB manufacturing concerns. The reason is they are so small and difficult to process. The 01005 package used for such passive devices as capacitors, resistors, and inductors causes the most anxiety since it is so small, it’s difficult to see with the human eye.
Small pad sizes on a wearable flex circuit may or may not provide sufficient bonding strength for the components to be soldered and assembled on the surface of that flex board. To assure that bonding strength, the following steps are critical. Factors that come into play in creating a sturdy flex circuit are based on:
- Direction of the bend of the circuitry
- Degree of bend
- Number of fold cycles
- Application types of the device
Plus, it’s important to factor in that flex circuits are designed to bend and twist, creating solder joint tensions in the assembly. If proper assembly isn’t performed, solder joints may crack, and/or dislodge components.