Issue link: https://iconnect007.uberflip.com/i/1323994
34 SMT007 MAGAZINE I JANUARY 2021 Get in the Right Mindset Proof of concept at the outset of prototyping isn't so much focused on ease of production and testability. Instead, the emphasis is more toward process development to find a work- able solution and a fully functioning product. This process typically can extend into two to three iterations, either in traditional SMT man- ufacturing or in PCB microelectronics labs. This is especially true for microelectronics assembly that has a cleanroom environment with extra sensitive material and special equip- ment for assembling medical insertable and ingestible devices. So, at the earliest prototype stages, the PCB assembly mindset must change. That means focusing on ease of production and testability rather than on process devel- opment. This would be difficult to practically implement, as proof of concept is the desired outcome rather than product maturity and pro- cess development. The next best thing would be to make the process mature and stable at the tail end of the prototype development. Although it may sound confusing, there must be assurances that the process is solid when transitioning from prototype to pilot runs. Dies, for example, need to be in a specific for- mat for pick-and-place machines to pick these up in the cleanroom. For example, when per- forming prototypes, there may or may not be a preference for the way dies are picked up. But for production, a well-defined process is abso- lutely necessary with even the minutest detail worked out. A diced wafer can be pulled through vacuum and placed on an interposer, substrate, or PCB. That is acceptable for five, 10, 15 or even 100 units. But when it comes to production, there are several aspects that need to be considered and incorporated into production runs for the pick-and-place stages for pick and place details along with fiducial marks on dies and substrates. Number one, dispensing material needs to be fully automated, regardless whether epox- ies or other materials are being dispensed on the board, substrate, or underneath the dies. This requires carefully dialing the dispensing parameters and making sure these substances are not under or over dispensed. Number two, especially when it comes to PCB microelectronics, an infrastructure com- bining machines and capabilities is critical to automatically pick up dies for production runs. These are dies that should be picked up from a common carrier, like waffle or gel pack rather than diced dies from a wafer. Also, there needs to be a pick-and-place high-speed die attach machine, as well as high-speed wire bond- ing equipment, to make sure production run speeds are properly maintained. Also, having the microelectronics assembly process conveyorized or in-line like in tradi- tional SMT manufacturing makes it production friendly. In a conveyorized microelectronics assembly, you can have a dispenser, pick-and- place machine, and wire bonder. Everything is conveyorized and in-line so that one function after another can be performed without physi- cal human intervention. This makes the whole process optimized, fast, efficient, and reliable. But, still, there are other things needed to make these production stages happen smoothly, effi- ciently, and optimally. Jigs, tools, and fixtures are needed to make the flow of different processes in multiple for- mats go through easily. You might have a fix- ture, jig, or tool that can do one product or placement at a time when dealing with small prototype quantities of 10 to 20 to 30 units. However, when you're talking about a few hundred to a few thousand units, specialized tools and fixtures that take multiple prod- ucts need to be produced to make the produc- tion optimized. We also have to look at the PCB—whether it's a flex board for ingestible or insertable devices, bio-degradable material for ingestible devices, or rigid-flex—to make sure they are manufactured in optimized pan- els, rather than one-up. Also consider that these are very tiny cir- cuit boards, and they are processed in panel form. Ten or so are on a panel that undergoes dispensing, pick and place, and wire bond- ing. Compared to traditional assembly, in this instance 10 boards are undergoing this assem- bly step versus one assembly at a time. The same process is repeated one time in a one-up setup versus the same process repeated