Small companies usually lack the dedicated engineering…
Small companies usually lack the dedicated engineering facilities required for prototyping parts with extremely fine pitch – getting BGA soldered at home is tremendously difficult and almost impossible. A nice way to get small companies interested in your product involves offering evaluation boards. These usually end up in a breadboard or a socket, where the pitch of 2.54 millimeters has established itself as a quasi-standard. This odd pitch, quite incidentially, dates back to imperial units – it is equal to 0.1 inch.
When designing such breakout boards, cost should not be the primary factor. Saving money on the headers is stupid – if they corrode, precision parts get problems. Due to that, using high-quality mechanicals from an established company such as TE Connectivity makes perfect sense.
The 5-146281-* family can be considered the standard offering for the 2.54mm standard. They are series of pins attached to one another, which can be broken down with scissors if smaller dimensions are needed. Acquiring them is not particularly difficult. TE Connectivity offer them in a range from 1 to 40 pins in a single row, the individual part numbers can be taken from the table.
…the part number contains information about the number of pins found in the header
The parts at hand should not be limited to Arduino shields and similar interfaces. They can also be used to create test points where an advanced debugging peripheral can be attached. The scope ranges from in certain in-circuit debuggers such as Microchip’s ICD family to custom testing rigs used for product development.
Interestingly, pricing can be an issue. The two-pin variant starts out at like 50 cents, while the 40 pin variant sets you back like 3.6€ – if you have time on hand, breaking parts down in-house is a neat way to reduce costs.