Note: Descriptions are shown in the official language in which they were submitted.
~ ~29514
Title
Press-Fit Terminal r,~ith Spring Arm
Contact for Edgecard Connector
Description
Tec nical Field
This invention relates to a new electrical
terminal for an edgecard connector for use in the
elect~ical connector industry, particularly in
microcircuits technology involving multiple circuit
10 hoard ~erminations. More particularly, this invention
relates to the manufacture and use of connectors having
elongated terminals which are press fit into circuit
board apertures and which have spring arm contacts
adapted for receiving and making electrical contact with
15 circuit boards.
Backqround Art
In the use of terminals for microcircuit
applications there is an ever-present need for
structures which are inexpensive to manufacture, yet
20 which possess inherentIy high degrees of reliability.
In the manufacture of press-fit terminals for mounting
in circuit board apertures, care must be exercised to
insure that tolerances between the board apertures and
the mountin~ portions of the terminals are within
25 certain preset limits. The limits must be adequate to
~ 1 ~
~1 ~1 f;) r? r~
v i t
~ 2
insure suffisient retention force, and Yet avoid injury
to metallization plating in the aperture. Many
s~ructures have been proposed for achievement of this
objective without substantial sacrifice in manufacturing
S costs and reliability of the terminations effected
thereby.
For example, U.S. 4,066,326, issued to
Lovendusky, discloses a circuit board contact with an
expanded mounting portion which will maintain a desired
retention force over a large circuit board aperture
tolerance. Circuit board terminals having similar
deformed mounting portions are also described in U.S.
3,827,004 issued to Vanden ~euvel et al. and U.S.
3,63~,819 issued to Evans. These structures, although
15 quite sufficient for their intended purposes, do not
provide sufficient retention force without solder
bonding when utilized in conjunction with wire wrap tail
contacts wherein the terminal may be subjected to
substantial torsional forces. Additionally, some of the
20 prior art structures (e.g., U.S. 3,634,81~) designed for
high force retention do not sufficiently insure accurate
location of the central axis of the mounting portion
within the circuit board aperture upon termination.
Press-fit terminals with spring arm contacts
25 are of~en used in edgecard connectors. Unfortunatiely,
such connectors built to provide high normal forces have
oeen asociated with undesirably high insertion forces,
as most of them utilize cantilever spring arm systems.
In order to provide satisfactory mating between the
30 board and spring arms, a sufficient normal force must be
created to assure firm electrical contact, but high
board insertion forces must be avoided. The typical
edgecard connector contains parallel opposing rows of
terminals having spring arm contacts biased toward each
35 other so as to define a convex contact engaging surface
for a mating board. The spring arms function as
. .
J 1 't
cantilever beams, so that when a board is slidably
inserted therebetween, the en~s of the spring arms are
Lorced lateraLl~ apart. Thus, the higher the normal
force provided, the greater t'ne insertion force.
5 Various structures have been proposed for achieving a
reduced insertion force per a given normal force, but
manY do so only marginall~, and most involve the
techni~ue of preloading the opposing spring arm contacts
as disclosed in U.S. 3,~3,~93 issued to ~cRee and U.S.
10 3,571,917 issued to Ammon et al.
Disclosure of the Invention
The elongated press-fit terminal of this
invention has a mounting portion which provides a 'nigh
retention force under torsional stress without solder
15 bonding. The mounting portion also provides accurate
central axis location in a circuit board aperture. The
edgecard connector of this invention provides a high
normal force with proportionally less insertion force
than realized in cantilever systems, while requiring no
20 preloading of the terminals contained therein.
The terminal mounting portion is a generally
cylindrical body with symmetrically opposed oval-shaped
voids rormed in the longitudinal dimension of the body.
The cross section is generallY bow-tie shaped with
25 symmetrically opposed dish-shaped impressions formed
therein to define a reduced center portion.
The edgecard connector contai~s a plurality of
elongated terminals having contacts at both ends and
which 'nave the above-mentioned mounting portion between
30 the contacts. One of the contacts is a wire wrap tail;
the other is a spring arm having a ~ree end parallel to
hut offset from the axis of the tail. The terminals are
press fit into apertures in a supporting circuit board
in parallel opposing rows. An insulative housing is fit
35 over the spring arm contacts and is mated with the
supporting circuit board. The hous-ng contains an
,. - ~ .
f ~ ~ ~1
. L . ,~ J V ~
opening adapted for removably receiving, in edgewise
fashion, a mating circuit board for electrical
connection ~etween the board and the spring arm
contacts. The housing has an inner wall which restricts
the free ends of the spring arms to movement only in
planès parallel to the axes of the wire wrap tails of
inserted terminals when a mating board is inserted into
the connector.
Brief Desc~tion of the Drawings
For better understanding of the advantages of
the present invention, reference will be made to the
accompanying drawings in which:
Figure 1 is a side elevation view of a
press-fit terminal of this invention attached to a
15 carrier strip;
Figure 2 is a front elevation view of the
press-fit terminal of Figure 1, including two such
terminals attached to a carrier strip;
Figure 3 is a front elevation view of the
20 deformed mounting portion of the terminal of this
invention;
Figure 4 is a cross-section view of the
deformed mounting portion of tne terminal;
Figure 5 is a cross-section view of the
25 deformed mounting portion after being press fit into a
circuit board aperture;
Figure 6 is a broken perspective view of an
alternate embodiment of the mounting portion of this
invention;
Figure 7 is an exploded perspective view of the
edgecard connector of this invention which utilizes the
terminal of Figures 1 and 2;
Figure 8 is a side elevation sectional view of
the edgecard connector of this invention which shows a
35 pair of opposed terminals positioned therein; and
.
, .
1 ~ L. ~
~a
Figure ~ is a side elevation sectional view of
the connector which depicts flexure positions oE the
spring arm contact of the terminal of this invention.
Desc~tion of the Invention
_
The elongated terminal 10 of this invention is
shown in Figures 1 and 2. The terminal has a bifurcated
spring arm contact 12 at one end and a wire wrAp tail
contact 14 at the other. Intermediate the contacts is a
deformed mounting portion 16 adapted for press fitting
10 into apertures in a printed circuit board. Intermediate
the spring arm contact and the mounting portion is a
first shoulder 18, a neck 20, and a second shoulder 22.
The terminal 10 is integrally attached to a carrier
strip 24 from which it is severed at reduced section 26
15 for press fitting into a circuit board aperture. The
spring arm contact 12 when severed from a carrier strip
has a free end 15 parallel to and offset from the axis
17 of the wire wrap tail 14 as may be observed in
Figure 1. The offset feature, however, is not essential
20 to the operability of this invention.
Figure 3 is an enlarged view of the mounting
portion 16 of the terminal 10. The body of the mounting
portion 16 is generally cylindrical with symmetrically
opposed oval-shaped voids 28 impressed therein by a ~ -
25 die. The najor axes 30 of the oval ~Joids extend
parallel to the longitudinal axis 32 of the mounting
portion 16. The cross section 3a of the mounting
portion 16 is shown in Figure 4. It is generally
~ow-tie shaped with symmetrically opposed dish-shaped
30 sections 36 impressed therein to form a reduced center
portion 38. The reduced center portion 38 is designed
to plastically deform upon the press fitting of the
mounting portion 16 into a circuit board aperture ao as
shown in Figure 5. Deformation of the center portion 38
35 occurs prior to the realization of injurious pressure
fitting forces. Thus, referring to Figure 5, the
~ . 9 51 ~,
pressure exerted by the contact surface 42 of the
mo~nting portion 16 against the metallization plating 44
in the aperture is thereby controlled to avoid (1)
injury to the plating 44, and (2) extreme deformation of
the aperture 40. At the same time, the contact surface
42 is large enough to afford high rates of retention
force ~ithout solder bonding in terminations subiected
to substantial torsional forces as, for example, those
encountered in the llse of wire wrap tails.
Although, the mounting portion of this
invention provides a high retention force without solder
bonding, the application of solder may be utilized for
an even higher retention force. Thus, Figure 6 is a
broken perspective view of an alternate embodiment of
15 the mounting portion 16 in a cross section of the
aperture 40. A mass of solder 46, shown as a globule,
is contained within a support hole 48 formed within the
shoulder 22 of the terminal. As the shoulder 22 is
contiguous with the mounting portion 15, the mass of
20 solder is positioned so as to flow into interspaces 50
(Fig. 5) between inserted mounting portion 1~ and the
aperture 40 upon exposure to an external heat source,
such as an infrared heater.
The elongated terminal 10 of this invention is
25 adapted for use in an edgecard connector 60 as shown in
Figures 7 and 8.
Figure 7 is an exploded perspective view of the
connector 60 which contains a plurality of the terminals
10. The terminals are press fit into apertures 40 in a
30 supporting circuit board 52 in opposing parallel rows as
shown. An insulative housing 70 fits over the spring
arm contacts 12 of the terminals 10 and is mated with
the supporting board 52 by mechanical fasteners not
shown. The housing 70 has an opening 72 adapted for
35 removably receiving a mating circuit board 80 in
edgewise fashion as depicted.
:., : : . -:, -:
~1 1 t ) ( ~ !--1 ,"
The circuit hoard 80 has metalliz~tion pads 82
prlnted t~lereon by conventional screen printing
techniques. The pads 82 are electrlcally connected ~o
other electrical elements, not shown. The edgecard
5 connector 60 provi~es a mecnanism by which mechanical
and electrical contact may be ac'nieved between the
metallization pads 82 and the spring arm contacts 12
contained within the housing 70.
Figure 8 is an elevation setional view of the
10 assembled edgecard connector 60 which shows a pair ~L
opposed terminals 10 positioned within the housing 70
for receiving mating circuit board 80. The housing 70
has an internal wall 74 parallel to the 3xes 17 of the
wire wrap tails 14 of inserted terminals 10.
In Figure 9, one of the spring arms 12 is shown
in both unflexed and flexed pos-tions (the latter in
phantom). The free end 15 of the spring arm 12
maintains contact with the wall 74 in both positions
shown as well as between positions. The wall restricts
20 the free end 15 to slidable movement along a plane
parallel to the axis 17 of tlle wire wrap tail l~ of an
inserted terminal 10. The spring arm 12 functions
therefore as a leaE spring ins-tead of the typical
cantilever spring used in most edgecard connectors.
25 Thus, as seen in Figure 8, since the free ends 15 of the
spring arms 12 cannot move laterally, they will not be
forced apart upon insertion of a mating board so as to
produce the nigh rates of insertion forces associated
with cantilever systems. Rather, a much lower insertion
30 force is reali~ed for a given normal force value in the
leaf spring system of this invention.
Industrial Ap~licablility
The press-fit terminal and edgecard connector
of this invention have wide applicability in micro-
35 circuits applications involving electrical terminationsbetween circuit boards. For example, such
C
' _L ~_ ~J~ L-~
devices are mounted in electrcnic backplanes of
computers, telephonic switching gear, and many ot'ner low
voltage si~nal systems.
Having thus described the best mode of the
invention, making reference to certain specific
embodiments thereof, the appended claims are intended to
cover such modifications as may fall within their scope.
