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PCB007-May2020

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60 PCB007 MAGAZINE I MAY 2020 Article by Brandon Sherrieb and Steve Karas INTEGRATED TEST CORPORATION Background Since consumers are driving requirements for smaller handheld devices with all the same functions as previous generation products, PCBs are being driven to smaller feature siz- es and decreased pad and drill pitch, all with increased layer counts and decreased plated through-hole to inner layer trace and plane spacing. This is especially true in the automat- ed test equipment PCB market, which builds the PCBs that interface between testers, prob- ers, or sockets and, finally, the device under test. These PCBs ultimately test all the func- tionality of the chips that go into cellphones, tablets, laptops, smart cars, and many other types of portable electronics. Customers in this market are pushing PTH pitch to less than 0.40 mm, with PTH to inner layer trace and plane spacing of less than 0.0035", all with high layer counts of 40 or more. This is regularly pushing drill aspect ratios to greater than 35:1, which is significantly increasing the difficulty in the drilling and plating departments. As this evidence suggests, this market is starting to demand PCBs with design attributes that far exceed traditional PCB manufacturing process capabilities. To overcome this at Integrated Test Corpora- tion, we have developed in-house design and manufacturing processes using conductive sin- tering paste in addition to processes utilizing board-to-board connectors. These processes are designed such that tighter pitch areas are fanned out to areas with a more manageable drill pitch that is then connected through one of the aforementioned methods to another PCB. This allows the more difficult tight pitch areas to be processed multiple up on a smaller PCB where layer counts can be reduced, and items like PTH-to-layer and layer-to-layer registra- tion can be better controlled due to the smaller panel size. Another advantage is that the PCBs can be fully completed through the manufac- turing process and tested before attaching to the less complicated PCB that has also been fully tested. In addition to the aforementioned benefits, others include reduced cost and pro- cessing time with increased yields. Another significant benefit is that since everything is Characterization of Advanced Interconnect Technology

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