603 Pin Socket Design Guidelines

4.2. Determination of Maximum Electrical Resistance:

This section provides a guideline for the instruments used to take the measurements.

Note: The instrument selection should consider the guidelines in EIA 364-23A.

a) These measurements use a 4-wire technique, where the instruments provide two separate

circuits. One is a precision current source to deliver the test current. The other is a precision

voltmeter circuit to measure the voltage drop between the desired points.

b) These separate circuits can be contained within one instrument, such as a high quality micro-

ohmmeter, a stand-alone current source and voltmeter, or the circuits of a data acquisition

system.

c) Measurement accuracy in Ω is specified as ± 0.1% of reading, or ± 0.1 m Ω, whichever is

greater. The vendor is responsible for demonstrating that their instrument(s) can meet this

accuracy.

d) Automation of the measurements can be implemented by scanning the chains through the edge

or cable test connector using a switch matrix. The matrix can be operated by hand, or through

software.

e) Measure R

Total

for each daisy chain of “interposer + socket + motherboard” unit.

f) Measure R

jumper

for each daisy chain of 30 “interposer + motherboard” units. Calculate

jumper

R for each daisy chain (There is 30 data for each daisy chain).

g) For each socket unit, calculate

jumper

Total

Req

−

Req

is the average contact resistance for socket pin.

4.3. Inductance:

The bottom fixture for the inductance measurement is a ground plane on the secondary side of the

motherboard with all pins grounded. The component side of the socket PCB does not contain a plane.

The top fixture is the interposer, which contains pins that will connect to the socket. Figure 4-4 shows

the inductance measurement fixture cross-section and the inductance measurement methodology. The

first figure shows the entire assembly. The second figure shows the assembly without the socket; the

socket-seating plane of the interposer is directly mounted to the component side of the socket PCB.

This is used to calibrate out the fixture contribution. The materials for the fixture must match the

materials used in the processor. Note the probe pad features exist on the topside of the top fixture, and

the shorting plane exists only on the bottom side of the bottom fixture. Figure 4-5 presents the

inductance and capacitance fixture design.