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Design007-Oct2020

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32 DESIGN007 MAGAZINE I OCTOBER 2020 A ball grid array (BGA) device can be a daunting component to route, especially in fine-pitch arrays featuring solder ball counts in the hundreds and pitch values as tight as 0.5 millimeters. With so much new technol- ogy requiring high-functioning processors and boards in increasingly miniaturized devices, it's safe to say higher pin density, reduced lead inductance, and finer-pitch BGA devices will become even more common in our industry. That means the foreseeable status quo will be less and less space to route traces and vias between pins. BGAs represent a challenge from design through prototyping and manufactur- ing, but with some sharp attention to detail and a plan focused on best practices, this is by no means an impossible task. Let's look at how you can take the mystery out of BGA rout- ing and create a PCB design that can handle all those pesky narrow spaces. Start With a Little Research BGAs have been around a while, so there are many resources available to provide some guidance and help you not to reinvent the wheel. There are some good online resources that can be very helpful, such as YouTube vid- eos, blog posts, and technical papers. Most of these resources are free to access, leaving you to sift through the marketing noise and extract available learning that will be useful to you. Know Where Trouble Can Lurk Solder joints are where you really need to mind your Ps and Qs. Smaller surface areas reduce the strength of the solder connection and increase the risk of fracture. Thermal issues can create flex between the component and board and put additional stress on the sol- der joints. Keep this in mind as you conduct research into BGA best practices. Vet Your Information Sources Device manufacturers will often have helpful information on their websites, such as routing exam- ples and land patterns. Typically, the part manufacturer's footprint is optimized for soldering the part to the board but can leave you with an impossible routing solu- tion. It's important to learn when to follow their guidance and when to improvise in the name of man- ufacturability and functionality. In most cases, it's acceptable to reduce the BGA pad size suf- ficiently to allow for vias between Unraveling the Mysterious BGA Routing Mess Connect the Dots by Bob Tise and Matt Stevenson, SUNSTONE CIRCUITS

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