U.S. patent application number 11/945724 was filed with the patent office on 2008-03-20 for cap for an electrical connector.
This patent application is currently assigned to FCI Americas Technology, Inc.. Invention is credited to Donald K. JR. Harper.
Application Number | 20080070443 11/945724 |
Document ID | / |
Family ID | 36596544 |
Filed Date | 2008-03-20 |
United States Patent
Application |
20080070443 |
Kind Code |
A1 |
Harper; Donald K. JR. |
March 20, 2008 |
CAP FOR AN ELECTRICAL CONNECTOR
Abstract
An electrical assembly that may include a weighted cap. The
weighted cap may provide counterbalancing to a non-proportional
ball-grid array connector integrated circuit package for connection
with a substrate. The weighted cap provides compensation for
variations in the imbalance of the electronic connector package
against the substrate.
Inventors: |
Harper; Donald K. JR.; (Camp
Hill, PA) |
Correspondence
Address: |
WOODCOCK WASHBURN, LLP
CIRA CENTRE, 12TH FLOOR
2929 ARCH STREET
PHILADELPHIA
PA
19104-2891
US
|
Assignee: |
FCI Americas Technology,
Inc.
|
Family ID: |
36596544 |
Appl. No.: |
11/945724 |
Filed: |
November 27, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11757523 |
Jun 4, 2007 |
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11945724 |
Nov 27, 2007 |
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11019779 |
Dec 21, 2004 |
7255601 |
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11757523 |
Jun 4, 2007 |
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Current U.S.
Class: |
439/607.05 |
Current CPC
Class: |
H05K 2201/10446
20130101; H01R 12/707 20130101; H05K 2201/10189 20130101; H01R
13/514 20130101; H01R 43/0263 20130101; H05K 3/3405 20130101; H05K
2203/159 20130101; H05K 3/3436 20130101; H01R 13/502 20130101; H01R
12/724 20130101 |
Class at
Publication: |
439/608 |
International
Class: |
H01R 13/648 20060101
H01R013/648 |
Claims
1. A method for mounting an electrical connector to a substrate
comprising: placing the electrical connector onto the substrate so
that a connector fusible element substantially aligns with a
contact pad on the substrate; providing a cap for the electrical
connector, wherein the cap has a geometric center offset from a
center of gravity of the electrical connector; placing the cap onto
the electrical connector to counterbalance the electrical
connector; and heating the electrical connector and the substrate
to create at least one electrical connection there between.
2. The method of claim 1, wherein the connector is a ball-grid
array connector.
3. The method of claim 1, further comprising placing the cap onto
the electrical connector with a vacuum head.
4. The method of claim 3, further comprising releasing the cap from
the vacuum head onto the electrical connector before heating.
5. The method of claim 1, wherein the cap comprises a recess and
the placing step further comprises mating the cap recess with the
electrical connector.
6. The method of claim 1, wherein placing the cap onto the
electrical connector causes the electrical connector to balance in
equilibrium across the fusible element.
7. The method of claim 1, further comprising removing the cap from
the electrical connector with the a vacuum head after heating.
8. The method of claim 1, wherein said heating is performed by
comprises a solder reflow process.
9. The method of claim 1, wherein the cap comprises a center of
gravity that is offset from an electrical connector center of
gravity.
10. The method of claim 9, wherein the cap center of gravity
differs from the cap geometric center.
11. A method for mounting an electrical connector to a substrate
comprising: aligning the electrical connector with the substrate so
that a connector fusible element substantially aligns with a
contact pad on the substrate; providing a cap for the electrical
connector, wherein the cap has a center of gravity that is offset
from a center of gravity of the electrical connector; placing the
cap onto the electrical connector to counterbalance the electrical
connector; and heating the electrical connector and the substrate
to create at least one electrical connection there between.
12. The method of claim 11, wherein the cap has a geometric center
that differs from the cap center of gravity.
13. The method of claim 11, wherein the step of placing comprises
using suction to move the cap and place the cap onto the electrical
connector.
14. The method of claim 13, wherein the cap comprises a recess and
the placing step further comprises mating the cap recess with the
electrical connector.
15. The method of claim 11, wherein the step of heating comprises
flowing solder.
16. The method of claim 11, wherein the connector comprises a
plurality of fusible elements, and the substrate comprises a
plurality of pads, and the step of aligning further comprises
aligning each of the fusible elements with one of the pads.
17. The method of claim 16, wherein the step of heating comprises
heating all of the fusible elements to create an electrical
connection between each fusible element and one of the pads.
18. A method for mounting an electrical connector to a substrate
comprising: aligning the electrical connector with the substrate so
that a connector fusible element substantially aligns with a
contact pad on the substrate; providing a cap for the electrical
connector, wherein the cap comprises a cap geometric center and a
cap center of gravity, the cap center of gravity differing from the
cap geometric center and being offset from a center of gravity of
the electrical connector; using suction to mate the cap onto the
electrical connector by mating a cap recess with the electrical
connector; and heating the electrical connector fusible element to
cause the fusible element to flow and thereby create at least one
electrical connection between the fusible element and the pad.
19. The method of claim 18, wherein the connector comprises a
plurality of fusible elements, and the substrate comprises a
plurality of pads, and the step of aligning further comprises
aligning each of the fusible elements with one of the pads.
20. The method of claim 19, wherein the step of heating comprises
heating all of the fusible elements to create an electrical
connection between each fusible element and one of the pads.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/757,523, filed Jun. 4, 2007, which is a divisional of U.S.
application Ser. No. 11/019,779, filed Dec. 21, 2004, the contents
of which are incorporated by reference herein in its entirety. This
application claims priority to these applications.
FIELD OF THE INVENTION
[0002] The invention relates generally to electrical connectors.
More specifically, the invention relates to a cap for an electrical
connector that weights the connector to facilitate mounting of the
connector on the surface of a substrate.
BACKGROUND OF THE INVENTION
[0003] Electrical connectors, such as ball-grid array (BGA)
connectors, are usually mounted on the surface of a substrate using
multiple solder connections. The solder connections act as
electrical and mechanical connections between the substrate and
contact pads on the connector.
[0004] The weight of some BGA connectors is not distributed evenly
across the solder balls (or other fusible elements). For example,
the center of gravity of some BGA connectors, such as right angle
BGA connectors, may be offset from the geometric center thereof to
an extent that causes the connector to tilt (or tip) on the
substrate. Such tilting can vary the pressures on the solders ball
of the ball-grid array. In other words, the weight of the connector
may be distributed unevenly among the solder balls. Such uneven
distribution can result in differences in the collapsing properties
and the height of the solder balls as the solder balls are melted
to form electrical connections. These factors degrade the strength
and integrity of the resulting solder connections. In extreme
cases, tilting can result in separation of the solder ball from the
associated contact pad, thereby inhibiting the formation of an
electrical connection.
SUMMARY OF THE INVENTION
[0005] A preferred embodiment for a method of mounting an
electrical connector to a substrate includes placing an electrical
connector onto a substrate so that a fusible element substantially
aligns with the contact pad on the substrate, providing a cap for
the electrical connector where the cap has a geometric center
offset from its center of gravity, placing the cap onto the
electrical connector to counterbalance and reposition the center of
gravity of the electrical connector so that the weight of the
combined assembly is centered over the fusible area, and heating
the electrical connector and the substrate to create at least one
electrical connection between the electrical connector and the
substrate so that the fusible elements form into a common
geometry.
[0006] A preferred embodiment of a cap for a electrical connector
includes a body, where the body includes a substantially planar
first surface suitable for vacuum pickup, a second surface formed
to engage the electrical connector, and a center of gravity and a
geometric center where the center of gravity is offset from the
geometric center so that the cap balances the electrical connector
on the substrate fusible area when the cap is placed on the
electrical connector.
[0007] A preferred embodiment of an assembly includes a substrate,
where the substrate includes an upper side having at least one
contact pad for connection, an electrical connector, where the
electrical connector comprises a housing, an electrical conductor
mounted within the housing, a fusible element attached to the
electrical conductor for forming an electrical connection with the
substrate, a center of gravity, and a geometric center, where the
center of gravity of the electrical connector is offset from the
geometric center of the electrical connector along at least one
axis, and a cap for mating with the electrical connector, where the
cap comprises a body with a center of gravity and a geometric
center, where the center of gravity of the cap is offset from the
geometric center of the cap so that the cap relocates the center of
gravity of the combined assembly in alignment with the center of
the fusible area when the cap is placed on the electrical
connector.
[0008] A preferred embodiment of a method for mounting a ball-grid
array connector to a substrate includes placing the ball-grid array
connector onto the substrate so that a fusible element array
substantially aligns with an array of contact pads on the
substrate, providing a cap for the ball-grid array connector,
wherein the cap has a geometric center offset from its center of
gravity, placing the cap onto the ball-grid array connector to
counterbalance the ball-grid array connector, and heating the
ball-grid array connector and the substrate to create at least one
electrical connection between the ball-grid array connector and the
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing summary, as well as the following detailed
description of a preferred embodiment, are better understood when
read in conjunction with the appended diagrammatic drawings. For
the purpose of illustrating the invention, the drawings show an
embodiment that is presently preferred. The invention is not
limited, however, to the specific instrumentalities disclosed in
the drawings. In the drawings:
[0010] FIG. 1 is an exemplary view of a substrate and an electrical
connector showing a fusible area;
[0011] FIG. 2 is a perspective view of a right angle ball-grid
array connector;
[0012] FIG. 3 is an exemplary view of an insert molded leadframe
assembly of the ball-grid array connector shown in FIG. 2;
[0013] FIG. 4 is an exemplary view of the lower surface of a
ball-grid array connector shown in FIG. 2;
[0014] FIG. 5 is an exemplary exploded view of an electrical
assembly including a substrate, an electrical connector, and a cap
in a preferred embodiment of this invention;
[0015] FIG. 6A is an exemplary view of a substrate and electrical
connector;
[0016] FIG. 6B is an exemplary view of a substrate, an electrical
connector, and a cap;
[0017] FIG. 7A is a side view of an alternative embodiment of the
cap shown in FIGS. 5 and 6B, with a balancing portion of the cap in
a first position on a cap portion of the cap; and
[0018] FIG. 7B is a side view of the cap shown in FIG. 6A, with the
balancing portion of the cap in a second position on the cap
portion.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0019] The figures depict a preferred embodiment of a cap 200 for
use with a right-angle ball-grid array (BGA) connector 20. The cap
200 is described in conjunction with this particular type of
connector for exemplary purposes only; alternative embodiments of
the cap 200 can be configured for use with virtually any type of
surface-mounted connector. The figures are each referenced to a
common coordinate system 11 depicted therein.
[0020] The connector 100 is shown as being mounted on a printed
circuit board (PCB) 100. The use of this particular type of
substrate is depicted for exemplary purposes only. The connector 20
can be mounted on other types of substrates, such as printed wire
boards, backplanes, etc.
[0021] The connector 20 comprises an electrically-insulative
housing 27, and a plurality of insert molded leadframe assemblies
(IMLAs) 21 positioned within the housing 27 (see FIGS. 2 and 3).
Each IMLA 21 includes a plurality of electrical conductors 22 that
extend through an overmolded frame 24. The frame 24 is formed from
a suitable electrically-insulative material such as plastic. Each
electrical conductor 22 preferably includes a lead portion 26, a
pin (not shown) adjoining a first end of the lead portion 26, and a
blade contact 28 adjoining a second end of the lead portion 26.
Each IMLA 21 can include fifteen of the electrical conductors
22.
[0022] The electrical conductors 22 vary in length. The electrical
conductors 22 are arranged side-by-side within the housing 27, so
that the blade contacts 28 form a vertically-oriented column
adjacent to the front edge of the frame 24, and the pins form a
horizontally-oriented row along the bottom of the frame 24 (from
the perspective of FIGS. 2 and 3).
[0023] A fusible element is attached to each pin of the electrical
conductors 22. The fusible element can be, for example, a solder
ball 70. The solder balls 70 form a ball-grid array 71 on the
bottom of the connector 20, as depicted in FIG. 4. The solder balls
70 each contact an associated contact pad 120 on the PCB 100 which
defines the fusible area 122 when the connector 20 is mounted
thereon, as discussed below.
[0024] The electrical connector 20 has a mid-point (geometric
center) 50, and a center of gravity 60. The electrical connector 20
is not symmetric about the geometric center 50, when viewed from
the perspective of FIGS. 1 and 6A. In other words, the connector 20
is not symmetrically disposed about an axis extending in the "y"
direction and passing through the geometric center 50. The center
of gravity 60 therefore is offset from the geometric center 50 from
the perspective of FIGS. 1 and 6A.
[0025] It should be noted that the geometric center 50 and the
center of gravity 60 are depicted diagrammatically; the geometric
center 50 and the center of gravity 60 are not necessarily located
at the positions depicted in the figures. Moreover, the above
details of the connector 20 are presented for exemplary purposes
only. The principles of the present invention can be applied to
virtually any type of surface-mount connector.
[0026] The connector 20 is placed on the PCB 100 so that the solder
balls 70 each substantially align with a corresponding contact pad
120 on the PCB 100, as noted above. The solder balls 70 are
subsequently heated by a suitable process such as a reflow
operation. The heating melts the solder balls 70. The solder, upon
cooling, forms electrical connections between the pins of the
electrical conductors 22 and the associated contact pads 120.
[0027] The above-noted offset in the center of gravity 60 of the
connector 20 causes the center of gravity 60 to overhang the
ball-grid array 71, as shown in FIGS. 1, 5 and 6A. The weight of
the connector 20 (acting through the center of gravity 60), in
combination with the reactive force exerted by the PCB 100 on the
connector 20 by way of the solder balls 70, generate a
counterclockwise moment on the connector 20 (from the perspective
of FIGS. 1, 5, and 6A). This moment is denoted by the arrow 90 in
FIGS. 1, 5, and 6A. The moment 90, if not counteracted, can cause
the connector 20 to tilt, as shown in FIG. 6A, thereby causing at
least some of the solder balls 70 to lose contact with their
corresponding contact pads 120 or to not have a common
geometry.
[0028] The cap 200 can act as a counterweight that counteracts the
moment 90, thereby preventing the above-noted tilting of the
connector 20. The cap 200 comprises a solid body 250 having a first
surface 210 and a second surface 220. The first surface 210
preferably is planar, to facilitate pick-up of the cap 200 by a
vacuum pickup.
[0029] The second surface 220 is configured to engage the
electrical connector 20. In particular, the second surface 220
defines a cavity 222. The shape of the cavity 222 is substantially
similar to that of the uppermost portion of the connector 20, so
that the cap 200 fits snugly over the connector 20, i.e., the cap
200 fits over the connector 20 with minimal clearance
therebetween.
[0030] The body 250 is configured so that the cap 200 acts as a
counterweight to substantially balance the connector 20 when the
connector 20 is placed on the PCB 100. This is achieved by
configuring the body 250 to be non-symmetric about the mid-point
(geometric center) thereof, from the perspective of FIG. 5. (The
geometric center of the body 250 is denoted in the figures by the
reference numeral 260.) In other words, the body 250 is
non-symmetric about an axis extending the in "y" direction and
passing through the geometric center 260. In particular, the body
250 is configured with a receiving portion 225, a first side
portion 230 located to one side of the receiving portion 225 (from
the perspective of FIG. 5), and a second side portion 235 located
to the other side of the receiving portion 225.
[0031] The second side portion 235 is substantially larger than the
first side portion 230, as shown in FIG. 5. The weight of the
second side portion 235 therefore is substantially greater than
that of the first side portion 230. This feature causes the weight
of the body 250 to be distributed asymmetrically about the
geometric center 260 (from the perspective of FIG. 5). The center
of gravity of the body 250 therefore is offset from the geometric
center 260. (The center of gravity of the body 250 is denoted in
the figures by the reference numeral 270.) In other words, the
center of gravity 270 and the geometric center 260 are located at a
different positions along the "x" axis denoted in the figures.
[0032] Alternative embodiments of the cap 200, such as a cap 300
depicted in FIGS. 7A and 7B, can comprise a body 302 having two
separate portions, a cap portion 304 and a balancing portion 306,
in contradistinction of the one-piece, homogenous cap 200. The
balancing portion 306 can be selectively positioned on the cap
portion 304 so that the combined cap portion 304 and balancing
portion 306 perform the same balancing function as the cap 200.
[0033] Further, it should be noted that the geometric center 260
and the center of gravity 270 are depicted diagrammatically; the
geometric center 260 and the center of gravity 270 are not
necessarily located at the positions depicted in the figures.
[0034] The cap 200 preferably is constructed so that the cap 200
counterbalances the connector 20 when the connector 20 is placed on
the PCB 100, as noted above. More specifically, the second side
portion 235 of the cap 200 is sized so that the cap 200 generates a
clockwise moment on the connector 20 when the cap 200 is placed
thereon (this moment is denoted by the arrow 290 in FIG. 5). The
moment 290 offsets the moment 90 acting on the connector 20, and
thereby can reduce or eliminate the tendency of the connector 20 to
tip as shown in FIG. 6A. In other words, it is believed that the
combined center of gravity of the connector 20 and the cap 200 is
located over the ball-grid array 71, more specifically over the
center of the fusible area 105, so that the reactive force exerted
by the solder balls 70 in response to the weight of the connector
20 and the cap 200 does not cause the connector 20 to tip. The use
of the cap 200 thereby can help to align and maintain contact
between each solder ball 70 and its associated contact pad 120 when
the connector 20 is placed on the PCB 100 during installation. (The
combined center of gravity of the connector 10 and the cap 200 is
denoted by the reference numeral 300 in FIGS. 5 and 6B).
[0035] The cap 200 can be positioned on the connector 20 before or
after the cap 200 is placed on the substrate 100. For example, in
one preferred mounting process, the cap 200 is positioned on the
connector 20 before the connector 20 is placed on the substrate
100. The combined cap 200 and connector 20 are lifted and placed on
the substrate using an automated device that engages the first
surface 210 of the body 250 by way of a vacuum pickup. The
connector 20 can be subject to a reflow process that melts the
solder balls 70 and forms electrical connections between the
connector 20 and the substrate 100, as discussed above. The cap 200
can be removed after the solder has cooled to form the electrical
connections.
[0036] The foregoing description is provided for the purpose of
explanation and is not to be construed as limiting the invention.
While the invention has been described with reference to preferred
embodiments or preferred methods, it is understood that the words
which have been used herein are words of description and
illustration, rather than words of limitation. Furthermore,
although the invention has been described herein with reference to
particular structure, methods, and embodiments, the invention is
not intended to be first to the particulars disclosed herein, as
the invention extends to all structures, methods and uses that are
within the scope of the appended claims. Those skilled in the
relevant art, having the benefit of the teachings of this
specification, may effect numerous modifications to the invention
as described herein, and changes may be made without departing from
the scope and spirit of the invention as defined by the appended
claims.
[0037] For example, the particular configuration of the cap 200
described herein is tailored to the connector 200. The geometry and
relative dimensions of the cap 200 can vary with the type of
connector used. Moreover, alternative embodiments of the cap 200
can be formed integrally with the connector with which the cap is
used. In other words, alternative embodiments of the cap 200 can be
configured to remain on the connector after the connector is
installed on its associated substrate.
* * * * *