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74 SMT007 MAGAZINE I FEBRUARY 2020 One of the ways to boost performance in elec- tronics is to place components in closer prox- imity to one another or eliminate solder. Most electronic assembly guidelines have strict rules about component placement to ensure that the assemblies can be cleaned more efficiently fol- lowing assembly and allow space for compo- nent removal and replacement if they do not survive the high temperatures of the assembly process. When solder is not used, components can be placed closer together. The time of flight for signals can thus be reduced consider- ably. This also can reduce the energy required to transmit the signal across the assembly. As a side note, when you see the hundreds of I/O on a high pin count BGA, up to 80% are dedicated to power and ground and serve to help get the on-chip signals from one side to the other. Again, there are prospective bene- fits related to design efficiency and operation. When you fully familiarize yourself with the concept, you will come up with other benefits. Reliability Reliability is defined differently in differ- ent dictionaries, but the following one seems particularly well suited to the current discus- sion: The ability of an apparatus, machine, or system to consistently perform its intended or required function or mission, on demand, and without degradation or failure. Like qual- ity, it is somewhat fungible in that the specific demands can vary from product to product. The reliability implications for a child's toy are understandably different from those for an implanted heart pacemaker. In electronic products, there are many things that can go wrong, but when failures occur, either in assembly or in the field, the failure can be traced with high regularity to the sol- der or high-temperature soldering process. As mentioned earlier, the electronics industry has been in pursuit of the perfect set of materials and processes that assure first pass 100% yield of electronic products over its entire history without success. Materials and processes have unquestion- ably gotten better, but problems remain. Look at the table of contents and advertising of virtu- nations, which erased the advantage enjoyed by previous generation designers. If they had instead chosen a base grid pitch and depopu- lated the grid to get to their objective, all design would have been much simpler today. There is much more that can be said about this topic, including a discussion of grid-based versus shape-based routing, and that is a topic for a future article. However, what has been provided should provide a basic appreciation and understanding of the benefits. Cost There are numerous factors that need to be accounted for in a cost analysis. The major ones are materials and labor, but there are many less obvious factors that contribute to cost (inspection, test, rework and repair, machine maintenance, etc.). When solder is eliminated from the manufacturing process, numerous process steps are also eliminated as are the various process consumables, tools, and fix- turing associated with them. The impact is sig- nificant. Depending on the BOM, the savings could range from perhaps as low as 5% to per- haps 35%, maybe more. When you eliminate solder, you also elimi- nate the need for a PCB. The materials required are likely less expensive and potentially higher performing as the list of options is greatly expanded. Assemblies can be made smaller, and fewer layers are required (Figure 2). There are also appreciable energy and labor savings and other areas of savings if one applies objec- tive thinking to the subject, but this list should convey the potential. Performance Performance is a bit of a loaded word because it can be measured in many ways. The pro- spective performance boosts stem from some of the same things that help to reduce the cost. Countless millions of dollars were invested in creating materials that would withstand the high temperatures associated with lead-free soldering. When high temperatures are not required, the list of prospectively useful mate- rials expands significantly.