An interview with Chuck Adams, 2009-2010 IEEE-SA President, Ning Hua, IEEE Chief Representative China, and Bill Ash, IEEE-SA Strategic Program Manager, after IEEE Standards Association IoT forum in Beijing on June 7, 2012
IEEE Smart Grid Research:
IoT PCB things to consider for Startups
Because IoT appliances are so fresh new, you would believe that getting an IoT printed circuit board (PCB) project off the ground starts by reinventing the wheel and enduring a great deal of technical troubles and delays. That is most certainly not true.
However it doesn’t suggest IoT startups have a clear approach to stardom. Facing them is numerous design and manufacturing factors which are distinctive to these small products. These points to consider must be taken into consideration for the new IoT device to achieve success.
On the plus side, it’s a consideration for IoT startups to understand that the foundation for a successful cool product does exist. This implies experience and knowhow relating to the design, fabrication and assembly of these cutting-edge products are accessible. Also, the best advice is for discreet IoT product business owners and leaders to follow the recommendations that seasoned electronics manufacturing services or EMS vendors provide. These firms and their engineering employees already have undertaken the job with revolutionary IoT corporations in Silicon Valley entering into the early stages of this surfacing segment.
The PCB of an IoT unit is another beast than the traditional one, which is substantially larger and flat. IoT gadgets, on the other hand, are made up mainly of either rigid-flex or flex circuit assemblies, which come with their own groups of design layout, fabrication and assembly points to consider and intricacies.
A foremost consideration is to find veteran designers who have undertaken quite a lot of rigid-flex PCB designs. PCB space for an IoT unit is scarce. So you want the designer to have firsthand layout practical experience to proficiently design vital elements on that modest area.
At the same time, almost all IoT systems are not stationary; they get substantial movement and rotating. Right here, the veteran designer plays a key role in computing bend ratios and lifecycle iterations as a significant part of a design. Various other vital design layout points to consider comprise of signal trace thickness, number of rigid and flex circuit layers, copper weight and stiffener placement. Stiffeners are employed on flex circuits in order to guarantee elements attached with the flex circuit continue being closely in place to prevent itself from movement.
One more aspect to consider is through-hole part positioning in rigid-flex circuits. Why’s that pretty important? A lot of IoT devices are founded on surface mount device placement. But there could be through-hole elements, which are generally positioned on either the rigid section or the flex area of the board. Through-hole elements are normally employed to connect input/output or I/O signals to the exterior world. Like that, those signals can be shown employing an LCD or LED monitor. Through-hole part placement is a vital concern in an IoT device for the reason that when utilized on the flex part of the board, appropriate stiffeners need to be designed and employed for effective assembly.
And lastly in the layout category, the heat which elements generate is required to be deemed. IoT systems are progressively more complicated with rigid-flex and flex circuits featuring in excess of 12 – 14 layers. Some systems are digital. But increasingly more analog units are being employed in IoT units. Analog circuitry makes significantly more heat than digital ones. Consequently heat expansion and also contraction rate ought to be considered. In tech lingo, this is actually generally known as the Coefficient of Thermal Expansion or CTE and the good handling of it.
Selecting the right fabricator is significant and is linked to the EMS company you have chosen. The fabricator you expect needs to have IoT PCB fabrication practical experience. Among vital points to consider here are assuring strong adhesions between layers on both rigid and flex circuit sides, figuring out all of the crucial calculations and having a solid comprehension of when current transfers from the rigid side to the flex side.
Such fabricators must also get an in-depth knowledge of really small components for instance 0201 and 00105 device packages, package-on-package, and the employment of fine-pitch ball-grid array or BGA packaged devices.
In addition they should have expertise in designing boards with fairly tight tolerances in terms of footprint for those types of BGA devices, in terms of up-to-date capabilities like laser direct imaging for putting the solder mask on the board. They need to have laser drills for via drilling with sizes of 5 mils or under because these IoT units could be so tiny that a common drill size of 5 to 8 mils perhaps might not suffice. They could have to go to a 3 mil, meaning you will need to have an superior laser drilling capability in-house.
In the event that you are placing via-in-pad, it’s really a fantastic way to make use of the small land that’s available on the rigid-flex board, but it produces difficulties for assembly. If vias are not completely planar or flat in shape, it could be challenging during the assembly of those tiny BGA packaged devices. The reason is non-planar surfaces might risk the integrity of solder joints.
Sometimes via in pads leave bumps if they’re not scrubbed the appropriate way after having the vias and gold finish on top. When there are bumps, then the solder joints in the assembly for those tiny BGA balls in those IoT devices might not be an excellent joint. This may create spotty connections, which might be a greater issue to handle and solve. It all boils down to which EMS company you are using because they’re the ones who will discover the fabrication plant to make a thriving IoT product for you.
It’s essential to go to veteran EMS companies that have proficiently assembled IoT and wearable PCBs as they have specialized tooling and fixtures already available, which are needed for assembly to ensure that components are placed correctly, exactly and the printing is completed properly.
Printing can be a problem for IoT units. If it’s a rigid-flex board, then you will find there’s a difference between thicknesses of the rigid and flex circuit portions, signifying a special fixture is required to maintain the complete rigid-flex board planar or 100 % flat to get effective printing to become reached.
Startups really should be well prepared to pick the suitable manufacturing partners and EMS companies. This way they can make certain they have ample experience ahead of time to get the multitude of design, fabrication and assembly details effectively performed as they are key to a lucrative and timely IoT product release.