Innovative New Uses for Ceramic Column Grid Arrays from TopLine

Estimated reading time: 8 minutes

Shaughnessy: Do they cut it off with a laser?

Hart: Traditionally, planarization is not a laser cutting process. Typically it is a mechanical guillotine, or lapping and polishing process. TopLine uses a method involving lapping and polishing. The lapping wheel spins at about 125 RPM with silicon-carbide paper. After 20 seconds, the columns can be reduced to final length. Then we finalize it with a diamond polishing film to make the columns nice in cosmetic appearance. This again explains why columns are much more difficult to attach than solder balls. That's just one additional example showing why people have moved away from columns into BGAs.

Shaughnessy: Do you see this really making a comeback? Are you at the forefront of a major change here?

Hart: Actually, columns never went away. Mil-defense, aerospace industry and high-value computing prefer CCGA due to its ability to absorb tremendous swings in rugged environments. CCGA are not being designed out. The good news is that more and more applications are being designed that can benefit from the use of solder columns. In summary, there is an ongoing need for CCGAs.

Shaughnessy: Tell me about micro-coil springs. I understand that is a new innovation?

Hart:  Over the past 40 years the industry has tended to keep using traditional solder columns. It was time for someone to invent a new type of column. In 2012, the engineers at NASA did a lot of research and they invented the micro-coil spring to replace solder balls. The springs are tiny and stand upright on the pads. Typically micro-coil springs are 1.27 mm high and 0.5 mm in diameter. Since NASA is not in the business of commercializing their inventions, they offered a technology transfer to TopLine. Today, TopLine manufactures and sell micro-coil springs.

Shaughnessy: Impressive. But why micro-coil springs?

Hart: A spring is able to absorb shock and compressions because it's a spring. A chip package can compress and then bounce back to its original size. NASA determined through exhaustive testing, that a chip carrier can attain considerably more thermal cycles using micro-coil springs. How many more cycles? Recently, NASA did a test where micro-coil springs survived more than 20,000 thermal cycles. Typical device data sheets state the number of hours a device will survive at a steady state, such as an operating temperature or storage temperature. However, the actual life of a device is measured in thermal cycles.

If you start at room temperature, and then you bake your chip to +125°C, then you freeze it down to -40°C, then bring it back to room temperature, that's called one thermal cycle. A large size BGA may survive only a small number of thermal cycles. Maybe a large ceramic BGA might survive only to 300 cycles before delamination. A traditional solder column can survive 2,000 to 3,000 thermal cycles. That’s a significant improvement. NASA tested micro-coil spring and some survived over 20,000 thermal cycles. The micro-coil spring have higher survival rate than the traditional solder column.

Shaughnessy: That's cool. This is all stuff that you guys have developed on your own?

Hart: It has been an ongoing process. TopLine  is making it easier for customers who want CCGA packages by providing columns and the tools so that customer can make columns with their own packages. TopLine provides columns to do re-columnization process by taking the balls off and putting the columns on. TopLine's approach is to teach customers how to attach columns and provide them with the means to do it.

Shaughnessy: So, this is great for mil-aero, it's great for down-hole drilling, and that sort of thing.  Any application that’s very high-reliability, with lots of vibration, and lots of thermal cycles.

Hart: Yeah, that summarizes the applications where columns are superior to solder balls.

Shaughnessy: I’m sure it will be an interesting class and paper session.

Hart: Anyone who wants to learn more about columns can go to our website, www.CCGA.co (and it’s not .com). There are a lot of pictures showing the process, movies showing how columns are attached, etc.

Shaughnessy: Martin, thanks for your time today.

Hart: Thank you, Andy.

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