OEMs continue to demand greater functionality in smaller portable and handheld products, such as wearables and IoT devices. As a result, a number of attributes are demanded these days for PCBs in smaller mobile technologies. Along with those attributes come a host of challenges in terms of layout, fabrication, and assembly, plus assuring many of these devices can efficiently withstand mechanical vibrations.
Fine pitch BGAs and CSPs, micro BGAs, and micro CSPs pose a main reason for these challenges. For example, as shown in Fig. 1, extra fine pitch CSP devices are increasingly being used for mobile, wireless, wearable, and IoT devices.
One has to keep in mind that new and different techniques used at the PCB design layout stage have a general cost, manufacturing, and testing impact at fabrication and assembly of these products. At layout stage, signal routing poses one of the foremost design challenges. Due to the shrinking real estate and the PCB populated with complex devices, there is virtually little space left on the board for signal routing.
For an upfront look at some of the issues, here are some tips and hints to get you started on this subject.
- PCBs for small portable, mobile, wireless, and IoT devices require three to four mil traces rather than the six mil traces for more conventional PCBs. This means finding the right fab house.
- Smaller board sizes mean smaller via sizes thus smaller diameters and pad sizes are required.
- If SMT pads are not drilled precisely, chances increase of having half moons or break aways. Therefore, reliability becomes an issue.
- 0.4 and 0.3 mm pitch BGAs are being used for these smaller PCBs. Traces have to be routed at three to four mils at layout.
- Also, 60 to 80% of overseas assembly house are eliminated because they cannot assemble these fine pitch BGA devices on PCBs.
Today, mobile technologies OEMs can ill afford to relinquish quality and reliability to unknown suppliers because the end user demands constant high levels of operation from their mobile, wireless, wearable or IoT devices. Meanwhile, the experienced EMS provider must overcome the challenges these small products pose by continuing to improve on design, fab, and assembly techniques.