IC test socket (contactor)

01

Match the package, pitch, plating and contact technology

Johnstech's Pad ROL 100A ES-P data sheet describes a rolling-contact contactor for QFN, DFN and other pad-style packages, with contact designs for pitches of 0.3 mm, 0.4 mm and 0.5 mm and above. It pairs contact profiles with device platings: gold-plated contacts for matte tin and tin-based platings, and Low-Force XL-2 contacts for nickel-palladium-gold. Its ESD-protective housing or alignment plate material limits the triboelectric charge of the contactor to under 100 V. [1]

The HERØHF data sheet describes a spring-probe contactor for BGA, LGA, QFN and WLCSP devices, with spear tips for QFN and LGA and crown tips for BGA and WLCSP, pitches down to 0.3 mm and Pd-alloy probe tips. It lists force at test height of 16 g, 20 g and 25 g for its HF030, HF040 and HF050 probes and 21 g for HF080. [2]

Both data sheets state that the contactors can be used with a manual actuator for engineering characterisation; the rolling-contact data sheet gives the manual actuator a life of 10k+ insertions. [1] [2]

Give the supplier the device package drawing, pitch and lead or ball plating, pin count and pin map, test type (engineering, production or burn-in), handler or load-board interface, current per pin, highest test frequency, Kelvin requirement, temperature range, required contact life and cleaning interval, ESD requirement, and actuator type.

02

Check contact resistance, current, frequency, life and temperature

For the HERØHF spring-probe contactor, Johnstech lists contact resistance under 100 mΩ, current carrying capacity of 1.9 A at 100% duty cycle, −1 dB insertion loss and −10 dB return loss up to 90 GHz (ground-signal-ground, depending on pitch and housing material), test height of 1.0 mm, contact pin life of 500,000 cycles and a temperature rating of −65°C to 175°C, noting that mechanical life performance degrades above 155°C. [2]

For the Pad ROL 100A ES-P at 0.5 mm pitch, it lists frequency of 40 GHz+, current carrying capability of 3.1 A at 100% and a temperature range of −40°C to 155°C. [1]

Editorial note: insertion loss, return loss and current figures depend on pitch, housing and the ground arrangement, so ask for data measured in the configuration you will use.

Smiths Interconnect's DaVinci technical characteristics show the same trade-offs from another maker. Its DaVinci 112 socket for 0.8 mm pitch lists 67 GHz / 112 Gbps bandwidth at −1 dB, 3.7 A current carrying capacity, contact resistance below 80 mΩ, 0.95 nH loop inductance and 0.42 pF mutual capacitance, −55 to +120 °C operation and a 500,000-cycle life span. The finer-pitch DaVinci 45G and 56 list 45 GHz / 26 Gbps and 67 GHz / 56 Gbps at 3.0 A with 0.2–0.22 nH and 0.13–0.15 pF, rated for 200,000 cycles or more. Smiths adds that its insulated housing material deflects 0.050 mm on a 4,096-pin BGA, against 0.168–0.210 mm for the comparison materials it lists. [3]

Editorial calculation: on a 4,096-pin BGA, housing deflection of 0.05 mm against 0.21 mm is about a quarter of the travel lost at the centre of the array; compare that with the probe's travel (0.40–0.50 mm listed for the 45G and 56) to judge how evenly contact force is held across a large device. [3]

03

Compare an elastomer socket with the probe and rolling-contact designs

Ironwood Electronics publishes the electrical data for a third contact technology: its SG25-BGA-2051 socket for an 8 mm × 8 mm BGA at 0.65 mm pitch is built on an elastomer contactor rather than spring probes or rolling contacts. Ironwood states it operates at bandwidths up to 52 GHz with less than 1 dB of insertion loss in a ground-signal-signal-ground (GSSG) configuration, and gives a contact resistance of 20 mΩ per pin (typ.). [4]

The same page lists pin self inductance of 0.06 nH, mutual inductance of 0.019 nH, capacitance to ground of 0.129 pF, mutual capacitance of 0.017 pF, current capacity of 2 A per pin and a temperature range of −35 °C to +100 °C. Ironwood notes that the network-analyzer reflection measurements were taken with every pin except the pins under consideration terminated into 50 Ω, and that the socket mounts on the target PCB with supplied hardware, no soldering and two mounting holes, which leaves room to place decoupling capacitors close to the device. [4]

Editorial calculation: the elastomer socket's 2 A per pin is about 54% of the 3.7 A listed for the DaVinci 112 spring-probe socket, and its −35 °C to +100 °C range is 135 K wide against 240 K for the HERØHF (−65 °C to 175 °C). Check current and temperature before choosing a contact technology on bandwidth alone. [4] [3] [2]

04

Contacts, housing, compliance and actuator

05

Contact, life and current data a socket quote should carry

Johnstech, Smiths Interconnect and Ironwood figures fill the rows that have them; insulation resistance, withstanding voltage, weight and humidity were not given in these sheets.

06

Send the device, test and life data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Device: [package drawing; pitch; pin count; plating]
Test: [engineering, production or burn-in; tester or handler]
Electrical: [current per pin; highest frequency; Kelvin]
Mechanical: [test height; force; actuator]
Life: [insertions; cleaning interval]
Environment: [temperature range; ESD]
Volume: [sockets; spares]

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