Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2002-03-19
2004-03-23
Pert, Evan (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S1540PB
Reexamination Certificate
active
06710613
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the temperature testing of electronic components and, primarily, the testing of electronic quartz resonators, whose electrical parameters are temperature dependent. For testing, a batch of resonators is mounted in a temperature chamber and heated or cooled to a specific temperature. When the resonator response has settled, it is measured. The process is repeated at other predetermined temperatures. For the measurement a test instrument is switched sequentially to each resonator by either electrical or mechanical means.
FIGS. 1 and 2
give an example of prior art according to Reference
1
. They show a plurality of components
1
supported on a flat test ring
3
. Leads of each component are inserted in sockets
5
and
7
. The sockets are connected with a first series of electrical contacts
9
on one side of the test ring and with a second series of electrical contacts
9
on the opposite face of the ring. The test ring is mounted in a chamber
15
on a turntable means
17
which is linked via shaft
19
to a step motor
21
outside the chamber. An electrical connection assembly includes a pair of wiper springs
23
that, upon stepwise rotation, can connect the component leads to an adapter network
25
(such as shown in
FIG. 4
) connected to a measurement instrument
27
outside the chamber.
A source of coolant
29
controlled by a valve
31
releases coolant, which is circulated by a fan
33
through a vertical, central inlet bore to the temperature chamber
15
. A baffle
39
has an upper horizontal edge which directs the coolant through central apertures in the turntable
17
and test ring
3
and over the top of the ring, cooling the components before returning to fan
33
. For temperatures higher than ambient, a heater
35
is used to heat the circulating air and thereby the components. The temperature is sensed by sensor
37
.
The motor
21
indexes the series of electrical contacts
9
,
11
associated with each of the components
1
into electrical contact with wiper springs. The contact springs are connected via adapter network
25
with test instrument
27
.
Another disadvantage is a limited temperature uniformity. A paramount requirement for temperature test systems is temperature uniformity for all components, i.e. at all component locations. In this regard, the described system has an inherent limitation because the airflow generated by fan
33
is not concentric (symmetric) with test ring
1
.
To overcome this problem, another prior-art system according to Reference
2
is claimed to have symmetric airflow. It is shown schematically in
FIG. 3
, including a temperature chamber
39
, a cylindrical “test wheel”
41
, and a “chamber base”
43
including “heater, coolant, fan, and insulation”, providing an airflow indicated by arrows
45
.
Both described systems require, in addition to the temperature chamber, housing for the generation, conditioning, and guidance of the circulating airflow. This means “wasted” space, energy, and time for heating and cooling the additional volume and apparatus.
Another disadvantage of both systems is limited measurement accuracy. This is explained by reference to
FIG. 4
, in which a test instrument
51
is connected to a resonator
53
via an “adapter network”
55
that includes several resistances and a “load capacitance”
57
. High measurement accuracy requires that the length of the connection between resonator and adapter network be as short as possible. In both of the prior-art systems discussed above, this connection includes wiper contacts and wiper-terminals that connect to the resonator sockets. In contrast, the circuit according to the invention provides a direct, short (approximately 3 mm) connection from the adapter networks to the resonator terminals.
A further disadvantage of both described systems is the relative complexity of the thermal insulation, which has to conform to the outside of the cylindrical part of the chamber as well as to the rectangular housing for fan and heater, as shown in
FIG. 1
SUMMARY OF THE INVENTION
The approach can be summarized by referring to
FIGS. 5 and 7
.
FIG. 5
shows a cross section of a system according to the invention.
FIGS. 7
a
and
7
b
is a cross section and top view, respectively, of a section of the system of FIG.
5
. In both figures, a stepwise rotatable test ring
2
in a temperature chamber
4
includes guide holes
36
and electronic components
32
with terminals
34
. It can be rotated by a step motor
20
via a pin wheel
22
with drive pins
24
that engage in guide holes
36
. A vertically mobile contact head
26
includes guide pins
28
and contact pins
42
. It can be moved up and down by a pneumatic solenoid
30
. Each time the ring is rotated a step, the contact head moves down to first engage guide pins
28
with the guide holes
36
—thereby accurately aligning the contact pins
42
with the terminals
34
—and, upon further down movement, connecting the contact pins
42
with the terminals
34
. Electrical measurements are made by a test instrument (not shown) that is connected to contact pins
42
via an adapter network
40
. A centrifugal-fan wheel
8
is driven by a motor
10
and mounted concentric with test ring
2
so that the fan's radially expelled air, indicated by arrows
12
, flows across the ring, in parallel with the test ring surfaces. Air guides
14
guide the airflow over the test ring and heating/cooling elements
16
back to fan inlet
18
.
This approach overcomes the disadvantages of prior-art systems and provides:
1. low chamber volume and thermal mass, achieved by locating the test ring so it is concentrically surrounding the centrifugal fan.
2. high temperature uniformity in the temperature chamber, achieved by providing symmetric airflow in the chamber.
3. high accuracy for electrical measurement of the components, achieved by a short, direct connection between component and an adapter network.
4. precise alignment of the component's terminals with the contact pins, achieved by a re-alignment during each step of the test ring. High precision is essential because the dimensions of the component's terminals may be smaller than 0.5×0.5 mm.
5. high reliability and low cost, achieved by the simplicity of the design.
6. high thermal efficiency and simple application of thermal insulation, based on enclosing the system—including heater and fan—in one cylindrical housing.
REFERENCES:
patent: 5451884 (1995-09-01), Sauerland
patent: 5546405 (1996-08-01), Golla
patent: 5859540 (1999-01-01), Fukumoto
patent: 6075373 (2000-06-01), Iino
Fay Sharpe Fagan Minnich & McKee LLP
Pert Evan
Sansei Denshi Co., Ltd.
Tang Minh B.
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