- Contact Pitch for each Fuzz Button diameter: .010" diameter = .4mm/.5mm, .015" diameter = .65mm, .020" diameter = .8mm/1mm, .030" diameter = 1.27mm
- Fuzz Button Compliance/Travel: 15 - 30% of length / 20% nominal
- Minimum wall spacing between holes = .010"
- Minimum spacing of hole wall to body edge = .010"
- Recommended PCB pad plating: Hard gold over electroless nickel, 80 micro-inch gold over 200 micro-inch nickel over 0.5 to 1.0 ounce copper, but other industry standard plating should be acceptable as well.
- PCB pads should be larger than Fuzz Button diameter, round or rectangular in shape, with maximum via size filled.
- Lead traces are recommended to be buried with the PCB layers. If necessary, traces may run on top side if covered by solder mask, which will eliminate shorting.
- Solder mask must stay a minimum of .002" away from the perimeter of the PCB pads.
Interposers with Fuzz Buttons only
- We recommend the Fuzz Button protrude on either side at .005" to .008" each in the uncompressed state. This allows for easier alignment while also guarding against Fuzz Button "fall-over" causing a short between two adjacent PCB pads. When the interposer is sandwiched between 2 opposing PCBs, the Fuzz Buttons become flush to the surface plane.
- Optimal travel for a Fuzz Button is 15 - 30% of its length in the uncompressed state, but values outside of this range are usually acceptable, especially if only a single mating is required.
- The holes in the interposer body should be just slightly larger than the Fuzz Button diameter. Examples: For .020" Fuzz Button, holes should be .0220" to .0225" (depending on the carrier thickness), while for a .010" Fuzz Button, the holes should be ~.0110" and for a .015" Fuzz Button, the holes should be ~.016". This allows for easier insertion while also ensuring the Fuzz Buttons remains in place during handling and assembly. These numbers are just
guidelines and it is recommended that customers do some local testing since there could be variations due to carrier material characteristics and thicknesses.
- To aid insertion of the Fuzz Buttons and to also better guide their travel/compression, we recommend a 45 - 60 degree lead-in hole chamfer on both top and bottom sides.
- Minimum body thickness is .030" which supports the other stated design rules.
Test Sockets & Interposers with Fuzz Buttons & Hardhats
- The body requires a 2 drill counterbore operation, whereby the bottom hole portion is larger than the top portion. This ensures the Hardhat shoulder is stopped by the smaller hole diameter, so the Hardhat does not come out of the top side.
- The recommended Fuzz Button pre-load on the bottom side is .010", while the Hardhat on the topside should be designed to protrude by ~.010" in the uncompressed state. Once compressed, the Hardhat becomes flush to the surface plane.
- The minimum recommended Fuzz Button length for this type of stack-up is .060", however, a length of .080" to .100" would be more ideal to provide greater durability and travel.
Interposer/Socket Material Choices
Ultem® Ultem 1000) is our go-to material offering low out-gassing, superior isolation, high structural strength and very light weight. Ultem 2300 is another great choice.
FR4 / G-10
Other dielectric plastics
Aluminum Alloys (many coatings/platings available)
Brass (commonly gold-plated)
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