Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-11-25
2002-08-06
Karlsen, Ernest (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S765010, C356S401000
Reexamination Certificate
active
06429671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to semiconductor device electrical test systems, and more particularly to semiconductor device electrical test systems employing probe cards with removable probe heads.
2. Description of Related Art
A wafer fabrication process typically forms multiple identical integrated circuits upon and within frontside surfaces of each of several semiconductor wafers processed as a group (i.e., lot). Each individual integrated circuit is formed within a die area of one of the semiconductor wafers. Following wafer fabrication, the dice are subjected to “wafer sort” electrical testing, then separated from the wafers. Fully functional die are typically packaged and sold as individual semiconductor devices.
Wafer sort electrical testing is performed to ensure each integrated circuit functions properly according to a predetermined electrical specification. Following wafer fabrication, each wafer is typically placed upon a flat surface of a test system with the frontside surface facing up. A wafer under test is raised up until bonding pads of one of the integrated circuits contact many fine wires or “test probes” of the test system. The test system may provide electrical power to the integrated circuit via some of the test probes, and may provide input signals and/or receive output signals from the integrated circuit via other test probes. The wafer under test is lowered, repositioned, and raised again until all of the integrated circuits formed on the wafer under test have been tested.
A modem integrated circuit may have several hundreds of very small bonding pads arranged within a rectangular die area having a surface area of about half a square inch. As a result, several hundreds of closely spaced test probes may be required to carry out the electrical testing during wafer sort. The fine wire test probes are delicate and easily damaged. Further, they are typically uninsulated, and must remain spaced apart to prevent shorting and to reduce inter-probe capacitance.
A typical modem test system includes a “probe card” which functions as an electrical interface between the test system and the device under test. The probe card effects a transition from relatively large electrical conductors (i.e., wires) used within the test system to the fine wire test probes which contact the bonding pads of the device under test.
FIG. 1
is a bottom plan view of a typical probe card
10
which includes a circular printed circuit board (PCB)
12
having two opposed surfaces. Probe card
10
may be, for example, a COBRA® probe card (Wentworth Laboratories, Brookfield, Conn.). One surface of PCB
12
is connected to a metal mounting ring
14
about a periphery. An alignment ring
16
and an interface circuit
18
are connected to the other surface of PCB
12
. A removable probe head assembly
20
including a probe head body
22
is adapted for mounting within alignment ring
16
as shown.
FIG. 2
is a sectional view of typical probe card
10
as indicated in FIG.
1
. Probe head body
22
has a pair of opposed surfaces and a set of probe holes extending between the opposed surfaces. The probe holes are arranged according to a pattern defined by electrical contacts
26
on a surface of a device under test
28
. Electrical contacts
26
may include solder bumps formed upon flat metal pads as shown in FIG.
2
.
Probe head assembly
20
includes a set of contact probes
24
each having two ends. Each contact probe
24
extends through a probe hole in probe head body
22
such that the ends of contact probe
24
project outwardly from the opposed surfaces of probe head body
22
. A pair of alignment pins
25
a-b
protruding from probe head body
22
fit into corresponding holes in alignment ring
16
when probe head body
22
is coupled to alignment ring
16
.
PCB
12
has two sets of bonding pads: a first set of bonding pads
29
on the surface of PCB
12
to which mounting ring
14
is connected, and a second set of bonding pads
30
on the opposite surface of PCB
12
adjacent to interface circuit
18
. PCB
12
includes electrically conductive metal traces, insulated by fiberglass-epoxy dielectric material, which interconnect bonding pads
29
and bonding pads
30
. Bonding pads
29
are connected to the test system, and bonding pads
30
are connected to corresponding bonding pads of interface circuit
18
.
Interface circuit
18
has a set of bonding pads
32
on one of two opposed surfaces, and a set of contact pads
34
on the other of the two opposed surfaces. Bonding pads
32
are located on a surface of interface circuit
18
adjacent to PCB
12
, and are connected to corresponding bonding pads
30
of PCB
12
. Contact pads
34
are electrically conductive flat metal pads formed flush with a surface of interface circuit
18
opposite PCB
12
. Contact pads
34
are arranged according to the pattern defined by electrical contacts
26
on the surface of device under test
28
. Interface circuit
18
includes electrically conductive metal traces, typically insulated by a ceramic dielectric material, which interconnect bonding pads
32
and contact pads
34
.
During testing, probe head body
22
is brought proximate the surface of device under test
28
such that one end of each contact probe
24
contacts a corresponding electrical contact
26
on the surface of device under test
28
. When probe head body
22
is properly aligned with and mechanically coupled to interface circuit
18
, the other end of each contact probe
24
contacts the corresponding contact pad
34
of interface circuit
18
. Electrically conductive signal paths are formed between the test system and contact probes
24
via PCB
12
and interface circuit
18
. The test system provides electrical power and input signals destined for device under test to bonding pads
29
on PCB
12
, and also monitors output signals produced by device under test
28
via bonding pads
29
. The electrical power, input signals, and output signals are conveyed to and from device under test
28
via electrical signal paths formed through PCB
12
, interface circuit
18
, and contact probes
24
of probe head assembly
20
.
Correct operation of the test system requires proper alignment between probe head body
22
and interface circuit
18
. As described above, interface circuit
18
is firmly attached to PCB
12
. Screw fasteners are typically used to attach alignment ring
16
to PCB
12
, and to attach probe head assembly
20
to alignment ring
16
. Subject to mechanical wear and tear, probe head assemblies are routinely removed from probe cards for maintenance and repair.
A problem arises when attaching probe head assembly
22
to alignment ring
16
following maintenance or repair. The mechanical tolerances associated with the screw fasteners are great enough to require tedious and time consuming manual adjustment of the alignment between alignment ring
16
and PCB
12
, as well as the alignment between probe head assembly
20
and alignment ring
16
, in order to attain correct test system operation. It is noted that alignment pins
25
a-b
reduce, but do not eliminate, the mechanical alignment problem. As probe head body
22
is typically opaque, visual verification of alignment between probe head body
22
and interface circuit
18
is made impossible, essentially reducing the alignment process to one of trial and error.
It would thus be desirable to have a probe card which provides for alignment of the probe head body directly to the interface circuit, and an associated alignment method. Such an apparatus and method would eliminate the required tedious and time consuming manual adjustment of the alignment between alignment ring
16
and PCB
12
, and between probe head assembly
20
and alignment ring
16
, in order to attain correct test system operation following replacement of a probe head assembly.
SUMMARY OF THE INVENTION
The problems outlined above are in large part solved by an electrical test probe card including a removable probe head assembly with alignment features
Duckworth Koby L.
Gilliam Timothy Eric
Islas Miguel L.
Advanced Micro Devices , Inc.
Conley & Rose & Tayon P.C.
Daffer Kevin L.
Karlsen Ernest
LandOfFree
Electrical test probe card having a removable probe head... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrical test probe card having a removable probe head..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrical test probe card having a removable probe head... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2975488