The Ball Grid Array, or BGA package is no longer the exclusive preserve of large, complex chips on computer motherboards: today even simple microcontrollers are available with those little solder balls. Still, many hobbyists prefer to stay with QFP and QFN packages because they’re easier to solder. While that is a fair point, BGA packages can offer significant space savings, and are sometimes the only choice: with the ongoing chip shortage, some other package versions might simply be unavailable. Even soldering doesn’t have to be complicated: if you’re already comfortable with solder paste and reflow profiles, adding a BGA or two into the mix is pretty easy.
In this article we’ll show that working with BGA chips is not as difficult as it may seem. The focus will be on printed circuit board design: how to draw proper footprints, how to route lots of signals and what capabilities your PCB manufacturer should have. We’ll cover soldering and rework techniques in a future article, but first let’s take a look at why BGAs are used at all.
What’s All This Ball-Grid Stuff, Anyhow?
As computer technology advanced in the 1990s, the motherboards inside our PCs became more and more complex. The 8-bit data buses from the 1980s gave way to 16-bit, 32-bit and even 64-bit wide buses between the CPU, the main memory and expansion cards like hard disk controllers and display adapters. These buses all had to be carried into and out of various chips, which therefore needed lots of pins.
The typical package for complex chips at the time was the quad-flat-package (QFP), with long rows of gull-wing shaped pins on each side. When scaled up to a pin count of 200 or more, these ..
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