Electrical circuit testing apparatus

A connector apparatus which is useful in testing electrical circuits where it is desired to mate test equipment to conventional integrated circuit sockets is disclosed. Spring probes make electrical contact with integrated circuit socket pins. J-shaped members of the apparatus have fingers which engage conventional integrated circuit sockets between the socket and a circuit board to clamp the apparatus to the socket. Fasteners lock the apparatus in this clamped position.

BACKGROUND OF THE INVENTION 
This invention relates generally to connectors. Specifically, the present 
invention relates to connectors which may be useful in the testing of 
electronic circuits. More specifically, the present invention relates to a 
plug type of connector which mates with a conventional integrated circuit 
socket. 
In testing electronic circuits, an integrated circuit (IC), such as a 
microprocessor or read only memory (ROM), may be removed from its IC 
socket. A plug connector, which electrically interfaces to test equipment, 
such as a microprocessor emulator or ROM simulator, then replaces the 
removed IC in the IC socket. In a production testing environment this plug 
connector must be inserted and removed from IC sockets many times every 
hour. Thus, a thin coating of highly conductive metal on the plug 
connector's pins tends to rapidly wear out. Additionally, the plug 
connector pins often risk bending. Accordingly, a need exists in the art 
for a plug connector which does not rapidly wear out or easily suffer from 
bent pins and yet easily connects and disconnects with an IC socket. 
Extension sockets have been used as one answer to this need. An extension 
socket contains pins which plug into the IC socket and sockets into which 
are plugged pins of the test equipment plug connector. The extension 
socket protects the test equipment plug connector from experiencing the 
high frequency of insertion and removal described above. However, the pins 
of the extension socket now experience this high frequency. Thus, the pins 
of the extension socket may rapidly wear out or easily bend. Therefore, 
extension sockets are often replaced. This involves a considerable expense 
of money and time and requires an on-hand supply of such extension 
sockets. Additionally, no quick connection and disconnection scheme is 
provided and an excessive amount of time may be consumed in inserting and 
removing the extension sockets from IC sockets. 
Spring probes, also called spring contact probes, compliant spring probes, 
and pogo-pins, are used in testing electrical circuits and may be used in 
probing connector sockets. These spring probes may be relatively rigid and 
resistant to bending. The spring probe is not actually inserted into a 
mating socket, and thus does not experience the wear problem of normal 
connector pins. Rather, spring probes make electrical contacts by being 
clamped to opposing contact points of the mating socket. 
In order for spring probes to effectively make a contact they must be 
retained and secured in proximity to the mating contact points. Various 
vacuum means, pressure plates, wedge plates, and specifically designed 
connector sockets having lugs and finger grips have been used to retain 
and secure spring probes in contact with opposing contact points. However, 
an IC socket typically is not equipped with any of these elements since it 
relies on friction to retain and secure an IC within the socket. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
improved plug connector which uses spring probes for pins and mates with 
conventional IC sockets without relying on an IC socket that has lugs or 
finger grips to secure the plug connector to the IC socket. 
Another object of the present invention concerns providing a improved 
spring probe connector plug which may be held in contact with a mating IC 
socket by a member which grips the IC socket between the IC socket and a 
printed wiring board. 
The above and other objects and advantages of the present invention are 
carried out in one form by an apparatus having a non-conductive base and a 
plurality of spring probes projecting perpendicularly away from a mating 
face thereof. The spring probes are spaced apart within the base to permit 
mating with a corresponding integrated circuit socket. Two J-shaped 
members are positioned on opposing sides of the base and project 
perpendicularly away from the base. Each of the J-shaped members has a 
finger portion which projects toward the other of the J-shaped members. 
The finger portions of the J-shaped members facilitate securing the 
apparatus to the integrated circuit socket by engaging a mounting surface 
of the integrated circuit socket.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 through 3 show various views of a first embodiment of the present 
invention. The first embodiment represents a plug connector which mates 
with a conventional 48 pin dual-in-line (DIP) integrated circuit (IC) 
socket. The DIP IC socket contains two parallel lines of isolated socket 
pins. In each line the center of each socket pin resides approximately 
one-tenth of an inch away from the center of an adjacent socket pin. 
Referring to FIG. 1, which shows a side view of the present invention, an 
IC socket 12 is mounted on a circuit board, such as printing wiring board 
(PWB) 10. IC socket 12 contains a multiplicity of socket pins 11. Each of 
pins 11 are soldered to PWB 10. IC socket 12 also contains an IC socket 
base 13 which is made of a nonconductive material which supports and 
defines the spacing between IC socket pins 11. A mating surface 32 of IC 
socket 12 opposes and is substantially parallel to a mounting surface 34 
of IC socket 12. Mounting surface 34 represents the surface of IC socket 
12 which faces PWB 10 when IC socket 12 is mounted on PWB 10, as shown in 
FIG. 1. 
An apparatus 14 represents a plug connector which mates with IC socket 12. 
Apparatus 14 contains a multiplicity of spring probes 18 which, when mated 
with IC socket 12, contact socket pins 11. Spring probes 18 are secured at 
one end thereof within a spacer 16 and project perpendicularly away from 
spacer 16 at a mating face 44 of spacer 16. Spacer 16 is constructed from 
a relatively rigid nonconductive material, such as Delrin.RTM. 
manufactured by DuPont. Spacer 16 holds spring probes 18 spaced apart from 
each other and in a spacial relationship which permits mating with IC 
socket 12 so that each of IC pins 11 contacts one and only one of probes 
18. 
When apparatus 14 mates with IC socket 12, spacer 16 resides between IC 
socket 12 and a header 15 portion of apparatus 14. An IC socket similar to 
IC socket 12 may be used for header 15. Header 15 contains a plurality of 
header pins 17 which are adapted to make an electrical connection to 
spring probes 18. 
Header 15 serves as an IC socket which mates with an IC connector plug 23. 
Connector plug 23 in-turn makes electrical connections to a ribbon cable 
24. Ribbon cable 24 may be connected to various electrical test equipment 
such as PROM simulators or microprocessor emulators (not shown). Thus, the 
test equipment can be electrically connected to circuits contained on PWB 
10 through ribbon cable 24, IC connector plug 23, header 15 and header 
pins 17, spring probes 18 and IC socket 12. 
Referring to FIG. 2, an exploded cross-sectional view of a single 
electrical connection is shown. A single wire within ribbon cable 24 
connects to a ribbon plug pin 26 within IC connector plug 23. Ribbon plug 
pin 26 mates with header pin 17 of header 15. Header pin 17 in the present 
embodiment is permanently secured within one end of a spring probe 
receptacle 29 by soldering. Spacer 16 supports spring probe receptacle 29. 
Spring probe 18 inserts into the other end of receptacle 29 and is 
retained within receptacle 29 by frictional force between spring probe 18 
and the interior surface of spring probe receptacle 29. As shown in FIG. 
2, spring probe 18 contains a spring probe contact 31 which can be brought 
into physical contact with IC socket pin 11. IC socket pin 11 makes an 
electrical contact with a trace (not shown) on PWB 10 by being soldered to 
the trace. 
Spring probe 18 contains a hollow spring probe cylinder 27. The interior of 
spring probe cylinder 27 contains a spring probe spring 28, and the 
exterior of spring probe cylinder 27 makes contact with spring probe 
receptacle 29. Spring probe 18 also contains a spring probe plunger 30 
which extends from within spring probe cylinder 27 on one end, through an 
opening in spring probe cylinder 27, to spring probe contact 31 on the 
other end. Spring 28 urges plunger 30 and contact 31 to a fully extended 
position where contact 31 is at a maximum distance away from spring probe 
cylinder 27. However, by application of a force on contact 31 in the 
direction of spring probe cylinder 27, contact 31 may move in the 
direction of spring probe cylinder 27 while cylinder 27 remains 
stationary. 
The present invention insures that a good electrical contact is maintained 
between spring probe 18 and IC socket pin 11. A low resistance contact 
which is not easily disturbed regardless of environmental conditions, 
orientations, or bumping, represents a good electrical contact. The 
present invention maintains this good electrical contact by causing 
contact 31 to physically touch and exhibit a predetermined force against 
IC socket pin 11. The exertion of the predetermined force is important in 
insuring that the electrical connection between spring probe 18 and IC 
socket pin 11 is a good electrical contact. However, this predetermined 
force must not be so great as to damage IC socket 12 or spring probe 18. 
Thus, spring probe spring 28 allows spring probe plunger 30 and spring 
probe contact 31 to travel toward spring probe cylinder 28 while exerting 
an effective force between contact 31 and IC socket pin 11. 
Spring probes 18 must be securely retained in a position near IC socket pin 
11 so that spring probe plunger 30 and spring probe contact 31 are 
displaced from the fully extended position towards spring probe cylinder 
27. The present invention provides a structure for securely retaining 
spring probes 18 in such position through the use of J-shaped members 19, 
as shown in FIGS. 1 and 3. 
Referring to FIGS. 1 and 3, for this embodiment of the present invention 
each of the J-shaped members 19 attach to spacer 16 at pivot points 20. 
Thus, J-shaped members 19 are hinged to spacer 16 and can be rotated about 
pivot points 20. 
In the present invention header 13 of IC socket 12 is displaced from PWB 10 
by a predetermined distance D. Distance D may be easily maintained between 
most conventional IC sockets 12 and printed wiring boards 10 because most 
conventional IC socket pins 11 contain a relatively wide collar portion 61 
(See FIG. 2) which projects beyond base 13 of IC socket 12. Collar portion 
61 is too wide to be inserted into a printed wiring board 10, so distance 
D may be easily maintained between base 13 and printed wiring board 10. Of 
course, those skilled in the art will recognize that even if an IC socket 
12 does not contain a collar portion 61 which projects beyond base 13, the 
distance D may be established by soldering IC socket pins 11 to PWB 10 so 
that base 13 does not contact PWB 10. 
Referring to FIGS. 1 and 3, J-shaped members 19 contain a finger portion 35 
of a thickness T and length L. The thickness T must be less than distance 
D described above. In the present embodiment, the thicknes T is 
approximately 0.030 inch, and the length L is approximately 0.100 inch. 
Each of J-shaped members 19 also contain an arm portion 36 from which 
finger portion 35 perpendicularly projects, a pivot beam 39 which also 
projects perpendicularly from arm 36 in the same direction as finger 35, 
and a handle portion 38 which connects on one end to an end of arm 36 at 
an obtuse angle. Resilient elements, such as springs 22, are inserted 
between handles 38 and spacer 16 to urge handles 38 outward from spacer 
16. When handles 38 are fully extended outward from spacer 16, J-shaped 
members 19 are in a normal position where fingers 35 are positioned toward 
the interior of apparatus 14. However, J-shaped members 19 may be placed 
in a mounting position by moving handles 19 against the action of springs 
22 toward spacer 16. 
To install apparatus 14, handles 38 of J-shaped members 19 are each 
depressed inward toward spacer 16. This action causes J-shaped members 19 
to pivot so that fingers 35 of J-shaped members 19 travel toward the 
outside of spacer 16. When handles 38 are fully depressed inward apparatus 
14 may be positioned relative to IC socket 12 so that spring probes 18 
physically contact corresponding IC socket pins 11. Then, by pressing 
apparatus 14 toward PWB 10 all of springs 28 (see FIG. 2) compress and 
apparatus 14 moves in the direction of PWB 10. This movement also causes 
fingers 35 of J-shaped members 19 to move in the direction of PWB 10. 
Eventually, apparatus 14 moves toward PWB 10, so that inward movement of 
fingers 35 will not be blocked by base 13 of IC socket 12. Now, fingers 35 
are free to move inward towards the central area of IC socket 12. Springs 
22 exert an outward force on handles 38 of J-shaped members 19 tending to 
cause J-shaped members 19 to pivot about pivot points 20. Thus, fingers 35 
of J-shaped members 19 tend to travel inward toward the central area of IC 
socket 12. The force which presses apparatus 14 toward printed wiring 
board 10 can now be removed. The collective action of springs 28 within 
spring probes 18 may cause apparatus 14 to move away from printed wiring 
board 10 a small distance until fingers 35 of J-shaped members 19 engage 
mounting surface 34 of IC socket 12. 
At this point apparatus 14 is securely retained relative to IC socket 12. 
J-shaped members 19 and fingers 35 releasably attach spring probes 18 to 
IC socket pins 11. Good electrical connections are maintained between 
spring probes 18 and IC socket pins 11 by the forces exerted from springs 
28 within spring probes 18. On one end of springs 28 forces are exerted on 
plungers 30 which urge contacts 31 toward PWB 10. At the other end of 
springs 28 forces are exerted through spacer 16, and J-shaped members 19, 
to fingers 35 and IC socket 12, urging IC socket 12 towards spacer 16. 
Referring to FIG. 3, an exploded perspective view from the mating face 44 
side of spacer 16 is shown. A reinforcement bar 40 constructed from a 
rigid material, such as aluminum, is installed in spacer 16. Reinforcement 
bar 40 prevents spacer 16 from distorting under the pressure exerted by 
spring probes 18 and thus helps maintain a good electrical connection for 
each of spring probes 18. Reinforcement bar 40 may be attached to spacer 
16 using a screw 43. 
Additionally, reinforcement bar 40 establishes pivot points 20 (see FIG. 
1). Reinforcement bar 40 contains grooves in opposing ends thereof which 
accommodate pivot beams 39 of J-shaped members 19. Pivot pins 42 are 
inserted into holes through reinforcement bar 40 which traverse the above 
mentioned grooves. Pivot beams 39 provide corresponding holes which 
accommodate pivot pins 42. Thus, when pivot pins 42 are inserted in 
reinforcement bar 40 and through pivot beams 39, pivot points 20 are 
established about which J-shaped members 19 rotate. 
In the present invention pivot points 20 are displaced toward the interior 
of reinforcement bar 40 from arms 36 of J-shaped members 19. When 
apparatus 14 is securely mounted to IC socket 12, pivot points 20 are 
displaced further towards the center of spacer 16 than the length L which 
defines the ends of fingers 35. This displacement of pivot points 20 helps 
J-shaped members 19 remain in the normal position in spite of external 
forces applied to apparatus 14. However, apparatus 14 may be removed by 
using the provided method of pressing handles 38 toward the center of 
spacer 16. 
FIGS. 4 through 6 show differing views of a second embodiment of the 
present invention. Although the first embodiment described above may be 
adapted for use with any number of socket types, the second embodiment may 
be particularly advantageous when the present invention mates with IC 
sockets having a relatively large number of socket pins. A large number of 
socket pins requires a large number of spring probes for mating therewith. 
The greater the number of spring probes, the greater amount of force that 
is required to depress all of the spring probes. Thus, when greater 
amounts of force are required to install apparatus 14 the second 
embodiment may be easier to install than the first. 
FIG. 4 shows an end view of the second embodiment of the present invention. 
Apparatus 14 is in an installation position relative to IC socket 12. 
IC socket 12 contains IC socket base 13 and IC socket pins 11. IC socket 
pins 11 project away from IC socket base 13 at IC socket mounting surface 
34. Additionally, IC socket pins 11 are attached to PWB 10 so that IC 
socket base 13 is positioned a distance D away from printed wiring board 
10, as discussed above in connection with the first embodiment. 
In the first embodiment J-shaped members 19 are pivotable members which 
perform the dual functions of grasping IC socket 12 and fastening 
apparatus 14 to IC socket 12. The second embodiment differs from the first 
embodiment in that J-shaped members 19 are combined with spacer 16 into an 
integral unit. In this second embodiment J-shaped members 19 do not pivot. 
Rather, J-shaped members 19 only grasp IC socket 12. A fastening function 
is performed in the second embodiment by a U-shaped member 46 which 
slideably attaches to spacer 16. 
In the second embodiment J-shaped members 19 contain J-shaped member arms 
36 which extend perpendicular to PWB 10 beside IC socket 12. J-shaped 
member fingers 35 are located at one end of J-shaped member arms 36 and 
extend parallel to PWB 10 in a direction which points toward the interior 
of apparatus 14. In the second embodiment, fingers 35 engage the mounting 
surface 34 of IC socket 12 along lines substantially parallel to lines 
formed by IC socket pins 11. 
Although FIG. 4 shows apparatus 14 in an installation position relative to 
IC socket 12, it shows apparatus 14 as not actually being installed. Thus, 
spring probes 18 are shown projecting from mating surface 44 of spacer 16 
but not yet contacting IC socket 12. Spring probes 18 rigidly attach to 
header 15 but not to spacer 16. Spring probes 18 are contained with 
openings through spacer 16 and are free to move within spacer 16 along the 
axial dimension of spring probes 18. 
Apparatus 14 may be installed with IC socket 12 by depressing header 15 
toward PWB 10 so that spring probes 18 contact IC socket pins 11 in a 
manner similar to that discussed above in connection with the first 
embodiment. U-shaped members 46 may then fasten or lock header 15 at a 
predetermined distance away from spacer 16. A force, which clamps 
apparatus 14 to IC socket 12, is collectively exerted from spring probes 
18 to header 15, through U-shaped members 46 to spacer 16 and fingers 35 
of J-shaped members 19. Reinforcing bars 40 are included to prevent 
distortion of header 15 from the pressure exerted by springs 28 (see FIG. 
2) of spring probes 18. 
FIG. 5 depicts a cross-sectional perspective view of the second embodiment 
of apparatus 14. In FIG. 5 a portion of IC socket 12 is shown with mating 
surface 32 facing the header 15 portion of apparatus 14 and mounting 
surface 34 facing the J-shaped member finger portion 35 of apparatus 14. 
Apparatus 14 may be positioned for installation to IC socket 12 by placing 
fingers 35 in a plane substantially defined by mounting surface 34 of IC 
socket 12. Apparatus 14 may then slide over IC socket 12 until IC socket 
12 abuts a backstop 59 portion of apparatus 14. At this point IC socket 12 
is positioned relative to apparatus 14 so that spring probes 18 directly 
oppose corresponding IC socket pins 11. 
In order to permit apparatus 14 to slide over IC socket 12, resilient 
elements, such as springs 55, urge header 15 and therefore spring probes 
18 away from fingers 35. Thus, spring probes 18 do not interfere with the 
sliding of apparatus 14 over IC socket 12. Screw 58 secures header 15 and 
reinforcing bars 40 to spacer 16. Additionally, screw 58 limits the travel 
of header 15 away from fingers 35. 
After apparatus 14 slides over IC socket 12 it may be installed to IC 
socket 12. As discussed above, the installation occurs by depressing 
header 15 toward spacer 16 and using U-shaped members 46 to fasten header 
15 in a predetermined spaced apart relationship with spacer 16. 
Each of U-shaped members 46 contain a short leg 47 substantially parallel 
to a long leg 48. Short leg 47 and long leg 48 are spaced apart from each 
other by a connection leg 50. Long leg 48 slideably attaches to spacer 16 
at a screw 51. A bushing 52 is provided so that U-shaped members 46 may 
freely slide relative to spacer 16 without binding at screw 51. A U-shaped 
member slot 54 is provided within long leg 48 of U-shaped member 46. 
Bushing 52 installs in slot 54. Screw 51 inserts through bushing 52 and is 
screwed into spacer 16. Thus, after header 15 has been depressed toward 
spacer 16 as described above, U-shaped members 46 are free to slide along 
an imaginary line (not shown) defined by screws 51. When U-shaped members 
46 are moved outward from apparatus 14 along this imaginary line, header 
15 may be moved toward or away from spacer 16. However, after U-shaped 
members 46 have been moved inward along this imaginary line, header 15 
becomes fastened in place relative to spacer 16 and cannot move away from 
spacer 16 because short legs 47 block such movement. 
FIG. 6 shows a side view of apparatus 14 installed with and secured to IC 
socket 12. Spring probes 18 contact IC socket pins 11 of IC socket 12. A 
constant force is exerted on each of IC socket pins 11 from individual 
ones of springs 28 (see FIG. 2) which are contained within spring probes 
18. First ends of springs 28 directly operate on plungers 30 and contacts 
31 of spring probes 18 (see FIG. 2). Second ends of springs 28 supply a 
collective force to header 15 which urges header 15 away from PWB 10. This 
force is transmitted to short legs 47 of U-shaped members 46, connection 
legs 50 and long legs 48 of U-shaped members 46, and to spacer 16. In the 
second embodiment J-shaped members 19 and fingers 35 are integral portions 
of spacer 16. Thus, this force is applied to mounting surface 34 of IC 
socket 12 from fingers 35. Resultingly, apparatus 14 is clamped to IC 
socket 12 and a good electrical connection is maintained at all IC socket 
pins 11. 
The foregoing description uses various embodiments to illustrate the 
present invention. However, those skilled in the art will recognize that 
changes and modifications may be made in these embodiments without 
departing from the scope of the present invention. For example, other 
fastening mechanisms may be used. The J-shaped members of the first 
embodiment may slide rather than pivot. Or, alternate fastening techniques 
to the U-shaped members of the second embodiment may be used. 
Additionally, a circuit board to which IC sockets may be attached is not 
limited to being a PWB as described herein. Furthermore, various types of 
spring probes are available and may be successfully adapted for use in the 
present invention. These and other modifications obvious to those skilled 
in the art are intended to be included within the scope of this invention.