BiTS 2008

Complete Zo=50 ohm
Coaxial Spring Probe IC Socket
Tatsumi Watabe
S.E.R. Corporation : Managing Director
1. Overview
IC Test Socket for SHF best performance, SER has realized
Complete 50 ohm Characteristic Impedance Coaxial Probe to use
for FBGA and CSP Testing. Complete Zo Coaxial Probe, theconcept is to do careful design for every portion detail on plungers,barrel, dielectric in coaxial to fit Zo=50 ohm and consider keeping
totally stable GND design for PCB, IC and Socket GND. The
Complete Zo Coaxial Probe has been confirmed the frequency
performance exceeded 20GHz on Transmission Performance. The
socket is available for 1.0, 0.8 and 0.5mm pitch.
The base socket is composed of 3 featured concept. (Photo.1)(1) Complete Coaxial Spring Probe(1)(2)

Contacts.
(2) Socket GND organize block.
(3) Regular composed Spring
Probe block.

(3)
Photo. 1
Complete Zo=50
ohm Coaxial Spring probe IC
Socket (0.5mm pitch)

11/2007

Best performance was brought froma combination of combining (1)and (2). It was confirmed by S
parameter loop measurementby specialized board andNetwork Analyzer using likeFig. 3. And total cost saving
comes from composing of (3).

BiTS 2008 Poster Guide & Template

1Dielectric

2. Complete Zo Coaxial Probe (1).
Because Characteristic impedance isdecided by the equation.
Zo=log(D/d) *138 / √Epsilon (ohm)Standard
CoaxialAll Coaxial probe portion from PCB
side (bottom) to IC terminal side (top)is designed to fit in Zo=50 ohm bychoosing and adjust Dielectric(Epsilon)
and diameter of plunger and barrel.

Complete
CoaxialThis example : Coaxial GND diameteris 0.9mm for 1.0mm matrix pitch and0.41mm for 0.5mm matrix pitch.

Fig. 1 Coaxial probe

3. Core probe for coaxial probe(1).
MD102-00

1.0mm (MD102-00) : diameters
Barrel 0.40mm Plunger 0.20mm,0.5mm (MD138-00) : diameters

MD138-00

Barrel 0.18mm, Plunger 0.18mm
are used (Fig.2). And deferent dielectric
are used for plunger portion and barrel
portion individually.

Fig 2. Coaxial core probe.

4. Coaxial GND is equate PCB GND(2).

GND

Photo 2. Socket GND organize

11/2007

It is distinguished highfrequency GND (analog GND on
this IC socket) to other GND.
Metal base is used for theCoaxial GND partially as Socket
GND organized to PCB GND .
Then IC GND was equalized toPCB GND by this composing.

BiTS 2008 Poster Guide & Template25. Measurement Condition.
High frequency signal source
through a Pico Probe touching tothe specialized board( characterized to Zo=50 ohm )holding Probe or Coaxial Probe beassembled as same condition of IC
base socket. And the signal returnto Network Analyzer by loop test
condition. (Fig 3.)

Fig 3. Measurement condition
通過特性

6. Probe S21 performance.

0-505101520A probe is designed with flung or
resistive belting on its surface
has a transmission performance
5 through 7 GHz only (Fig 4.). It
is not restricted by probe length
like Fig 4. For achieving max.

ｄB-10-15-20-25-30
GHｚfrequency performance, acore probe for coaxial must
be more efficient design for
SHF performance.

Fig 4. Probe performance restriction
MD0102-00 通過特性
0051015-520

7. Complete Zo=50 ohm
Coaxial probe performance.

ｄB-10-15-20-25-30
GHｚFig 5. Complete Coaxial
Probe Performance

20 GHz transmission performance
was measured. A conditioning ofcomplete Zo coaxial technique with,Socket GND equate techniquebrought this achievement for bothof 1.0 mm and 0.5 mm coaxial
probe socket by using MD102-00
and MD138-00 core probe. (Fig 5.)

Best design concept for IC Socket’s Probe and GND location isrequired to be best fitting to IC contact terminal matrix. I think It
will be needed more cooperated relationship enhancement
between ‘socket makers’ and user ‘IC users’ together.
11/2007

BiTS 2008 Poster Guide & Template3