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CONNECTING THE DOTS

Working with Board-to-Board Connectors

by George Martin

Start ı Off the Beaten Path ı The Chosen Path ı Marking the Path ı The Final Stretch ı Sources and PDF

OFF THE BEATEN PATH

Before I continue exploring other connector options, let me switch subjects and talk about costs. I use a standard cost of $0.10 a pin as a target price, and thatıs for a complete solution. Digi-Key has 3M 2 mm x 2 mm, 60-pin connectors for $7.74 (socket) and $4.99 (straight pin) in single quanities. These include a gold-plated contact area. In quantities of 500, prices drop to $5.32 and $3.44, respectively. Thatıs a total of $8.76 for 60 pins, slightly over my standard cost but acceptable. As you look at all the connector options available, make note of their prices. Some will surprise you because theyıre at both ends of the spectrum.

Another avenue to explore is the standard daughter card solutions, such as the ones used for DRAM modules, Futurebus+, VESA Media Bus, DIN, PCMCIA cards, or even Pentium II connectors. These are medium- and high-density connectors that are being built in high quantities, and that means low prices. These connectors are even appearing in distributorsı catalogs, so you know theyıre available. Some of them mount the daughter card at right angles to the main board, and others (like the DRAM connectors) mount the daughter card at an angle to the main board. This angle might give you additional packaging density.

Whenever Iım using a standard connector for a nonstandard application, I ask a couple of questions. What if my daughter card gets plugged into a standard application? What if a card from the standard application gets plugged into my unit? There is no easy answer to either question. The best Iıve come up with is to use the same signals on your card as the standard, or at least the same power. And, match inputs and outputs with the standard. Or, you can just not worry about it if your application is far removed from the standard. However, whatever you decide, write it up well in the manual.

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