Technical terms are used extensively — and sometimes misused — when it comes to IoT devices and the technologies they are rapidly absorbing. One such term is microelectronics, spoken and written about since the day the transistor was invented.
Today, microelectronics takes on another name — namely wire bonding, which again isn’t a new technology since semiconductor manufacturing has been using it since day one. What is new is that wire bonding has landed right squarely on IoT printed circuit boards and all other small PCBs.
Why, you ask, is wire bonding necessary for IoT PCBs? Here’s why: IoT circuitry is remarkably tiny in size. Plus, IoT devices are increasing in functionality, meaning even more circuitry is demanded on those small areas. The IoT PCB is extremely small, so small that conventional device packaging taking up valuable space has to be eliminated to make room for more and more circuitry to be placed on that PCB.
The bottom line is a bare, packageless chip is now placed on the board and connected by very thin wires going from the chip itself and bonded directly on the substrate or PCB. We’re talking about infinitesimally thin wiring, hundreds of times thinner than the conventional soldering wire that hobbyists use.
Wiring going into your IoT PCB may be gold, aluminum, copper or some other material. Wire thickness can be one, two, three, four, five or six mils. A mil equals one-thousandth of an inch or 0.001 inch. Typically, however, thickness of the wire used is one to three mils.
Wire bonding has two categories that go under that term: wedge and ball bonding, each distinctively different. Each requires separate and different sets of systems and temperatures for wire bonding operations. For wedge bonding, either aluminum or gold are typically used. For ball bonding, gold wiring is typically used. Wedge and ball bonding also differ in the way the wire bond is made on the chip side. The bond is made resembling a gold ball, while the end of the wire is in a wedge-shape for wedge bonding.
Inspection and verification are two critical aspects of precise IoT PCB wire bonding. The electronics manufacturing services (EMS) provider must use the correct inspection equipment. This wire bonding process requires that wire strength be accurately measured. Also, the wire’s loop radius between chip and board connections must be measured and verified. A high-end inspection system captures those minute connections via high-resolution video images, and then real-time measurement is performed.
While IoT wire bonding may not be rocket science, this major IoT PCB assembly process is critical and demands top expertise. So here, the EMS provider performing your IoT PCB assembly must have a keen knowledge, experience and advanced systems on the assembly floor to produce a successful product. He must be savvy enough to be able to assemble surface-mount packaged components along with wire-bonded devices on the same PCB.
Therefore, the IoT device OEM must closely partner with its EMS provider to assure the correct wiring is not only designated at the design and layout stages, but also accurately used in assembly and manufacturing. Further, a word of caution: The OEM must also keep in mind that many EMS providers may be latecomers as far as adopting wire bonding, and/or they may try to convince you they have the knowhow and capability and then farm it out to unproven contractors.
One has to be wary simply because they focus solely on earlier and conventional PCB technologies and not wire bonding. To assure you’re successful with your IoT product success, it’s important to first carefully vet potential EMS providers and then discuss your IoT assembly requirements, including their knowledge of IoT wire bonding.
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