U.S. patent application number 09/434682 was filed with the patent office on 2002-05-02 for circuit board apparatus with pin connectors.
Invention is credited to CUSTER, JAMES KEITH, ROBERSON, JAMES HIRAM, VEITSCHEGGER, WILLIAM KERR.
Application Number | 20020052146 09/434682 |
Document ID | / |
Family ID | 23725234 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020052146 |
Kind Code |
A1 |
CUSTER, JAMES KEITH ; et
al. |
May 2, 2002 |
CIRCUIT BOARD APPARATUS WITH PIN CONNECTORS
Abstract
A method allowing for the inexpensive automated construction of
interconnections between circuit boards is provided. According to
the present invention, printed circuit pins are inserted in a
circuit board from the top (component side). Provided the heads of
the pins are thin enough to lie beneath a solder stencil, the pins
may be pre-installed on the circuit board and solder applied to the
pins at the same time solder is applied to other regions of the
board. Thus, known surface mount techniques may be employed to form
solder connections between the pins and conductive traces on the
circuit board, which facilitates the automation of the previously
manual operation of soldering the printed circuit pins
separately.
Inventors: |
CUSTER, JAMES KEITH; (FAIR
OAKS, CA) ; ROBERSON, JAMES HIRAM; (PLACERVILLE,
CA) ; VEITSCHEGGER, WILLIAM KERR; (FOLSOM,
CA) |
Correspondence
Address: |
DAVID L. HENTY
MYERS,DAWES & ANDRAS LLP
19900 MACARTHUR BLVD.
SUITE 1150
IRVINE
CA
92612
US
|
Family ID: |
23725234 |
Appl. No.: |
09/434682 |
Filed: |
November 5, 1999 |
Current U.S.
Class: |
439/625 |
Current CPC
Class: |
H05K 3/3447 20130101;
H05K 2201/10303 20130101; H01R 12/523 20130101; H01R 12/58
20130101; H01R 12/7082 20130101; Y10T 29/49149 20150115; Y10T
29/49139 20150115; H05K 3/1216 20130101; H05K 2201/10871 20130101;
Y10T 29/49163 20150115; Y10T 29/49147 20150115; Y10T 29/49144
20150115; H05K 3/3485 20200801 |
Class at
Publication: |
439/625 |
International
Class: |
H05K 001/00 |
Claims
What is claimed is:
1. A method for forming a pin on a circuit board, comprising the
steps of: providing a circuit board having at least one first
component-side surface including at least one electrically
conductive trace and at least one bore therethrough; providing at
least one pin having a shaft portion, a friction segment and a head
portion; inserting said at least one pin into said at least one
bore in said first circuit board from the direction of said first
component-side surface whereby said shaft portion passes through
said bore and said friction segment frictionally engages said bore;
applying solder paste to the head portion of said at least one pin;
and heating the solder paste to melt temperature to form a soldered
electrical connection between the pin and said electrically
conductive trace of the circuit board.
2. The method of claim 1, wherein said step of applying solder
paste further comprises the steps of: providing a solder stencil
having apertures corresponding to the location of said at least one
pin; placing the solder stencil over the first component-side
surface; and applying solder paste to the stencil whereby said at
least one pin is coated with solder paste.
3. A method for forming an electrical connection between two
circuit boards comprising the steps of: providing a first circuit
board having at least one first component-side surface including at
least one first electrically conductive trace and at least one
first bore therethrough it; providing a second circuit board having
at least one second component-side surface including at least one
second electrically conductive trace and at least one second bore
therethrough it; providing at least one pin having a shaft portion,
a friction segment and a head portion; providing at least one
socket contact having a cavity defined therein; inserting said at
least one pin into said at least one first bore in said first
circuit board from the direction of said first component-side
surface whereby said shaft portion passes through said bore and
said friction segment frictionally engages said bore; applying
solder paste to the head portion of said at least one pin and
adjacent portions of said socket contact; applying solder paste to
the region adjacent said at least one second bore; inserting said
at least one socket contact into said at least one second bore in
said second circuit board from the direction of said second
component-side surface; heating the solder paste to melt
temperature to form a soldered electrical connection between the
pin and said at least one first electrically conductive trace of
the first circuit board, and between the socket contact and said at
least one second electrically conductive trace of the second
circuit board; positioning the first circuit board and the second
circuit board in proximity so that there is substantial alignment
between said at least one pin and the cavity in said at least one
socket contact; and inserting the shaft portions of said at least
one pin in the cavity in said at least one socket contact.
4. The method of claim 3, wherein said steps of applying solder
paste applying step further comprises the steps of: providing a
first solder stencil having apertures corresponding to the location
of said at least one pin; placing the first stencil over the first
component-side surface; and applying solder paste to the first
stencil whereby said at least one pin is coated with solder paste;
providing a second solder stencil having apertures corresponding to
the region adjacent said at least one second bore; placing the
second stencil over the second component-side surface of the second
circuit board; and applying solder paste to the second stencil
whereby the region adjacent said at least one second bore is coated
with solder paste.
5. A circuit board having pins, comprising: a circuit board having
at least one first component-side surface including at least one
electrically conductive trace and at least one bore therethrough;
at least one pin having a shaft portion, a friction segment and a
head portion, said at least one pin being connected to said circuit
board by: inserting said at least one pin into said at least one
bore in said first circuit board from the direction of said first
component-side surface whereby said shaft portion passes through
said bore and said friction segment frictionally engages said bore;
providing a first solder stencil having apertures corresponding to
the location of said at least one pin; placing the stencil over
said first component-side surface; applying solder paste to the
stencil whereby said at least one pin is coated with solder paste;
and heating the solder paste to melt temperature to form a soldered
electrical connection between said at least one pin and said
electrically conductive trace of the first circuit board.
6. The circuit board of claim 5, wherein the friction segment of
said at least one pin has a hexagonal cross-section.
7. The assembly of circuit boards of claim 5, wherein the friction
segment of said at least one pin has a knurled cross-section.
8. The assembly of circuit boards of claim 5, wherein the head
portion of said at least one pin is between substantially 0.004 and
substantially 0.010 inches thick.
9. An electrical interconnection between a first circuit board
having at least one first component-side surface, at least one
first electrically conductive trace, and at least one first bore
therethrough it, and second circuit board having at least one
second component-side surface, at least one second electrically
conductive trace, and at least one second bore therethrough it,
said electrical interconnection comprising: at least one pin having
a shaft portion, a friction segment, and a head portion; and at
least one socket contact having a cavity defined therein; said at
least one pin being connected to said first circuit board by:
inserting said at least one pin into said at least one bore in said
first circuit board from the direction of said first component-side
surface whereby said shaft portion passes through said bore and
said friction segment frictionally engages said bore; providing a
first solder stencil having apertures corresponding to the location
of said at least one pin; placing the stencil over said first
component-side surface; applying solder paste to the stencil
whereby said at least one pin is coated with solder paste; and
heating the solder paste to melt temperature to form a soldered
electrical connection between said at least one pin and said
electrically conductive trace of the first circuit board; and said
at least one socket contact being connected to said second circuit
board by: providing a second solder stencil having apertures
corresponding to the location of said at least one pin; placing the
second stencil over the second component-side surface of the second
circuit board, wherein the solder stencil has apertures
corresponding to the region adjacent said at least one second bore;
and applying solder paste to the second stencil whereby the region
adjacent said at least one second bore is coated with solder paste;
inserting said at least one socket contact into said at least one
second bore in said second circuit board from the direction of said
second component-side surface; heating the solder paste to melt
temperature to form a soldered electrical connection between said
at least one socket contact and said at least one second
electrically conductive trace of the second circuit board; said at
least one pin and said at least one socket contact being joined by:
positioning the first circuit board and the second circuit board in
proximity so that there is substantial alignment between said at
least one pin and the cavity in said at least one socket contact;
and inserting the shaft portions of said at least one pin in the
cavity in said at least one socket contact.
10. The interconnection of claim 9, wherein the friction segment of
said at least one pin has a hexagonal cross-section.
11. The interconnection of claim 9, wherein the friction segment of
said at least one pin has a knurled cross-section.
12. The interconnection of claim 9, wherein the head portion of
said at least one pin is between substantially 0.004 and
substantially 0.010 inches thick.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to interconnections for
propagating radio frequency (RF) signals between circuit boards.
More particularly, the present invention relates to a method for
using surface-mount techniques to mount and solder connectors
suitable for transmitting RF signals between two circuit
boards.
[0003] 2. Description of Related Art
[0004] Modern electronic circuits utilize components that operate
in the RF domain. It is often necessary to transmit RF signals
between two different circuit boards. For example, one may desire
to couple the signal from a coplanar waveguide on one circuit board
to a coplanar waveguide on another circuit board.
[0005] A coplanar waveguide is a type of high-frequency
transmission line formed by placing a central conductor, i.e. a
circuit trace, on the surface of one side of a circuit board,
between two closely-spaced circuit traces held at ground potential.
Additionally, a ground plane is placed on the reverse side of
circuit board (opposite the central conductor), in which case the
structure then becomes a coplanar waveguide with ground. A coplanar
waveguide is a substantially planar analogue of a coaxial cable
that has been sliced along its longitudinal axis to reveal a
central conductor surrounded by a grounded conductive sheath.
[0006] In order to transmit a signal between coplanar waveguides on
two different circuit boards, an interconnection must be provided
between the respective central conductors and ground planes on each
board. Care must be taken to keep the central conductor path
well-shielded to minimize signal attenuation due to radiation of
energy into the air. The design of an interconnection must also
minimize reflections, another source of signal attenuation. The
problems of radiation and reflection are general matters of concern
in the design of RF transmission lines, of which coplanar
waveguides are just one type.
[0007] Coaxial contacts, such as blind mate connector systems, have
been used conventionally to provide an RF path between separate
circuit boards or assemblies. However, the blind mate connector
systems are bulky and expensive, and thus increase the cost per
connection. They also require a manual operation to connect and
disconnect them, further increasing the cost of their use.
[0008] Short metal ribbon interconnections have also been used. The
metal ribbon interconnections are difficult to handle due to their
small size. They also have a further disadvantage of requiring
solder applications, often done manually, to complete the RF path.
These disadvantages greatly increase the cost of completing each
connection. Furthermore, metal ribbon interconnections cannot be
easily disassembled. When one desires to disconnect two boards, the
metal ribbon interconnections must be unsoldered.
[0009] A printed circuit pin and spring socket system has been used
conventionally as a connection system for circuit boards for
low-frequency analog, digital and power applications in
electronics. A disadvantage of this system is that the pin
connector is installed from beneath (i.e., opposite the component
side) a circuit board and soldered in place by hand. Automated
installation from the side opposite the component side requires
complicated and expensive assembly equipment.
[0010] Accordingly, there is a need for an inexpensive method for
installing a low-cost RF interconnection for providing a
low-radiation, low-reflection RF path between multiple circuit
boards or assemblies. There is also a need for an interconnection
that may be installed, connected, and disconnected without manual
operations.
SUMMARY OF THE INVENTION
[0011] In accordance with the teachings of this invention, a method
for forming an RF interconnection between circuit boards using pin
and socket connectors is provided. As described in more detail
below, the present invention provides several distinct advantages
over conventional methods of forming RF connections between circuit
boards. According to the present invention, printed circuit pins
are inserted in a circuit board from the top (component side),
which is a step that is easily automated. Another advantage
provided by having the pins inserted from the top side of the
circuit board is that it is possible to use surface mount
techniques to form solder connections between the pins and
conductive traces on the circuit board. Provided the heads of the
pins are thin enough to lie beneath a solder stencil, the pins may
be pre-installed on the circuit board and solder applied to the
pins at the same time solder is applied to other regions of the
board. This eliminates the conventional manual soldering operations
that are usually performed after other components have already been
soldered in place. Reducing the conventional two-step, partially
manual soldering routine to a single automated step provides a
significant advantage of manufacturing efficiency.
[0012] The printed circuit pins used in connection with the present
invention include a shaft located at the distal end of the printed
circuit pin and a head at the proximal end. The shaft has a
cylindrical cross-section and is dimensioned to be inserted through
a conductively plated bore through a circuit board and into a
socket connector. The head is wider than the plated bore through
the circuit board. Thus, the head prevents the printed circuit pin
from passing completely though the bore when the pin is inserted.
The shaft and head are joined by a friction segment and taper
region which form the intermediate portion of the printed circuit
pin. The friction segment is dimensioned to fit snugly in the
plated bore through the circuit board. The friction segment thus
provides an interference fit through friction between the printed
circuit pin and the plated bore through the PC board.
[0013] The assembly method includes a step of inserting the printed
circuit pin in a bore through a circuit board. The insertion may be
done by machine. The interference fit described above keeps the
printed circuit pin in position while succeeding steps involving
known surface mount techniques are applied to the circuit board. A
solder stencil is laid over the circuit board after pins are
inserted. Solder paste is applied to the solder stencil which
contains several apertures through which solder paste is coated on
regions of the circuit board lying beneath the apertures.
Specifically, there are some apertures lying over the heads of the
printed circuit pins, and the pins are consequently coated with
solder paste. The solder paste is then heated and reflowed, and
next cooled to complete the electrical connection between the
printed circuit pin and a conductive surface surrounding the bore
through the circuit board.
[0014] On another circuit board, solder paste is applied to regions
surrounding bores through the circuit board. Socket connectors are
then inserted through the bores. The solder paste is heated and
reflowed, and then cooled to complete the electrical connection
between sockets and a conductive surface surrounding the bores
through the circuit board.
[0015] Once the pins and sockets are installed on their respective
circuit boards, the interconnection is completed by mating the pins
with the sockets. The result is a low-radiation, low-reflection RF
path between the circuit board wherein the interconnection is
integrally a part of the circuit boards.
[0016] A more complete understanding of the invention will be
afforded to those skilled in the art, as well as a realization of
additional advantages and objects thereof, by a consideration of
the following detailed description of the preferred embodiment.
Reference will be made to the appended sheet of drawings which will
first be described briefly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A depicts a perspective view of two circuit boards
having RF conductive traces on the surface thereof and
corresponding bores through which printed circuit pins sockets may
be inserted for forming an interconnection;
[0018] FIG. 1B depicts view of conductive regions plated on the
top, component-side surface of a circuit board in relation to a
conductively plated bore;
[0019] FIG. 1C depicts a view of the conductive regions plated on
the bottom surface of a circuit board in relation to a conductively
plated bore;
[0020] FIG. 2 depicts a side view of a completed
interconnection;
[0021] FIG. 3A depict a perspective view of a solder stencil
overlaying a corresponding circuit board;
[0022] FIG. 3B depicts a side view of a solder stencil overlaying a
corresponding circuit board taken along line 1-1 of FIG. 3A;
[0023] FIG. 4 depicts a perspective view of a printed circuit pin
which may be used in connection with the present invention;
[0024] FIG. 5 depicts a view of the printed circuit pin taken along
line 2-2 of FIG. 4;
[0025] FIG. 6A depicts a side view of a printed circuit pin
partially inserted in a bore through a PC board;
[0026] FIG. 6B depicts a side view of a printed circuit pin fully
inserted in a bore through a PC board with solder paste applied to
its head;
[0027] FIG. 6C depicts a side view of a printed circuit pin after
solder paste applied to its head has been heated and reflowed;
[0028] FIG. 7A depicts a side view of a socket contact partially
inserted in a bore through a PC board with solder paste applied to
the PC board adjacent to the bore;
[0029] FIG. 7B depicts a side view of a socket contact fully
inserted in a bore through a PC board after solder paste has been
heated and reflowed;
[0030] FIG. 8A depicts an alternative embodiment of a printed
circuit pin which may be used in connection with the present
invention;
[0031] FIG. 8B depicts a view of the printed circuit pin taken
along line 3-3 of FIG. 8A;
[0032] FIG. 8C depicts an alternative embodiment of a printed
circuit pin which may be used in connection with the present
invention;
[0033] FIG. 8D depicts a view of the printed circuit pin taken
along line 4-4 of FIG. 8C.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The present invention satisfies the need for a method for
forming an inexpensive interconnection providing an RF path between
for multiple circuit boards or assemblies. The present invention
also satisfies the need for an interconnection that may be
installed, connected, and disconnected without manual operations.
In the detailed description that follows, it should be appreciated
that like element numerals are used to describe like elements
illustrated in one or more of the figures.
[0035] Referring now to FIG. 1A-C, a first circuit board 10 is
shown. A first RF conductive trace 12 is disposed on a
component-side surface 11 of the circuit board 10. The conductive
trace 12 lies between two electrical ground regions 13 formed from
conductive traces disposed on a component-side surface 11 of the
circuit board 10. Additionally, an electrical ground plane 17 is
disposed on the side of the circuit board 10 opposite the
component-side surface 11. It is well known in the art that an RF
signal may be propagated along the RF conductive trace 12. A second
circuit board 20 is also shown with an RF conductive trace 22 and
electrical ground regions 23 formed from conductive traces disposed
on a component-side surface 21 of the second circuit board 20.
[0036] The circuit boards 10, 20 have conductively plated bores 14,
24 through them. The conductive plating 15, 25 lining the bores 14,
24 is electrically connected to the RF conductive traces 12, 22 on
the circuit boards 10, 20. As illustrated in FIG. 1B and 1C, the
conductive plating 15 may have an component-side extremity 15a that
is in electrical contact with the first RF conductive trace 12. The
electrical contact between the conductive plating 15 and the RF
conductive trace 12 allows an RF signal to propagate along the RF
conductive trace 12 and through the circuit board 10 via the
conductive plating 15. For applications using a coplanar waveguide
with ground, the opposite extremity 15b of the conductive plating
15 is isolated from the ground plane 17 by a surrounding insulation
region 19. The insulation region 19 prevents the RF signal from
being shorted to ground. The second circuit board 20 is similarly
constructed. The circuit boards 10, 20 also may have additional
conductively plated bores 18, 28.
[0037] Referring now to FIG. 2, a completed interconnection is
depicted. A printed circuit pin 30 is shown inserted from the
component side through circuit board 10 and into socket 50 which
has been inserted through circuit board 20. The pin 30 and socket
50 pass through and are in electrical contact with the plated bores
as discussed in connection with FIGS. 1A-C.
[0038] Referring now to FIGS. 3A and 3B, a solder stencil 40 is
shown overlaying a circuit board 10. The stencil 10 contains
apertures 41 and 42 corresponding to regions of the circuit board
10 where solder paste should be deposited. Specifically, the
apertures 42 correspond to the regions in which printed circuit
pins 30 are located after they are inserted in the circuit board
10. The apertures 42 allow solder paste to be applied to the heads
35 of the printed circuit pins 30. There is a thickness 60 of the
solder stencil 40. The heads 35 must be thin enough that they can
be accommodated in the thickness 60. That is, the heads 35 must be
able to lie inside the aperture 42 of the solder stencil 40 without
interfering with its functioning. For example, the head 35 may be
about 0.008 inches thick and the thickness 60 may be about 0.010
inches thick.
[0039] Referring now to FIGS. 4 and 5, an embodiment of the printed
circuit pin 30 of the present invention is shown. The printed
circuit pin 30 has a proximal end and a distal end joined by an
intermediate portion. The printed circuit pin 30 includes a shaft
31 located at the distal end of the printed circuit pin 30 and a
head 35 at the proximal end. The shaft 31 and head 35 are joined by
a friction segment 33 and taper region 39 which form the
intermediate portion of the printed circuit pin 30. The shaft 31
has a cylindrical cross-section. The diameter and length of the
shaft must be such that it may be received in the inner cavity of a
socket contact. For example, the diameter may be about 0.025 inches
and the length about 0.155 inches. In the embodiment shown in FIGS.
4 and 5, the friction segment 33 has a hexagonal cross-section.
Alternative embodiments may use, for example, a regular polygonal
cross-section with more or fewer sides. The taper region 39 may
angle away from the shaft 31 at about forty-five degrees, although
other tapering angles are within the scope of the invention. The
portion of the printed circuit pin 30 including the taper region 39
and the friction segment 33 should have a length substantially the
same as the thickness of the circuit board 10, such as about 0.055
inches. The printed circuit pin may be made of a brass alloy
covered with a material with high conductivity and resistance to
oxidation. For instance, the brass alloy may be covered with a
nickel layer and finished with gold.
[0040] The construction of an interconnection will now be described
with respect to FIGS. 6A-6C. Referring first to FIG. 6A, the
printed circuit pin 30 is shown partially inserted through a bore
14 in the circuit board 10. The bore 14 is lined with an
electrically conductive plating 15. A conductive trace 12 is in
contact with the conductive plating 15. The friction segment 33 has
a diameter slightly larger than the bore 14 so that it fits snugly
within the bore 14, such that edges 37 of the friction segment 33
firmly contact the conductive plating 15 of the bore 14 when the
printed circuit pin 30 is inserted. The contact between the edges
37 and the conductive plating 15 creates an interference fit that
resists movement of the printed circuit pin 30. The head 35 is
shown to have a diameter slightly larger than that of the bore 14.
This dimension of the head 35 prevents the printed circuit pin 30
from being pushed completely through the bore 14 in the circuit
board 10.
[0041] FIG. 6B shows a printed circuit pin 30 that has been fully
inserted in a circuit board 10. A solder stencil is positioned over
the circuit board 10 so that the aperture 42 is in alignment with
the head 35 of the printed circuit pin 30. Next solder paste 70 is
applied to the head 35 and surrounding areas of the printed circuit
pin 30 through aperture 42. The solder paste 70 is then heated
causing it to melt and reflow around the head 35. Referring now to
FIG. 6C, the cooled and hardened solder 72 is shown after reflow.
The hardened solder 72 provides an electrically conductive path
between the conductive trace 12, the conductive plating 15 and the
printed circuit pin 30.
[0042] Referring now to FIGS. 7A and 7B, solder paste 53 is
deposited around a bore 57 through a second circuit board 20. The
bore 57 is lined with an electrically conductive plating 25. The
conductive plating 25 is in electrical contact with a conductive
trace 22 on the component-side surface of the circuit board 20.
Next, a socket contact 50 is positioned through the bore 57 and the
conductive plating 25 until a shoulder 52 of the socket contact 50
rests substantially flush with the conductive trace 22 and the
conductive plating 25. The solder paste 53 is then heated causing
it to melt and reflow around the shoulder 52 of the socket contact
50. After the solder paste 53 is cooled and hardened, the resulting
hardened solder joint 55 provides an electrically conductive path
between the conductive trace 22, the conductive plating 25, and the
socket contact 50. It will be understood by one skilled in the art
that the steps of inserting and soldering the printed circuit pins
30 and the inserting and soldering socket contacts 50 may be
performed simultaneously or in succession.
[0043] Referring now again to FIG. 2, a side view of a completed
interconnection is shown. The printed circuit pin 30 is shown
extending through the first circuit board 10 down into a socket
contact 50 which is dimensioned to receive the printed circuit pin
30. The socket contact 50 is disposed in a bore through the second
circuit board 20.
[0044] Referring now to FIGS. 8A-8D, some alternative embodiments
of the printed circuit pin 30 are shown. The essential feature of
the printed circuit pin 30 is that it provide an interference fit
when positioned within a plated bore 14, 24. The feature may be
provided by a wide variety of shapes. For example, FIGS. 8A and 8B
depict a printed circuit pin 30 having a friction segment 33 that
is square in cross-section. FIGS. 8C and 8D depict a printed
circuit pin having a friction segment 33 that has a knurled
cross-section.
[0045] A preferred method for constructing an interconnection
between microstrip lines on two circuit board having just been
described, it should be apparent to those skilled in the art that
certain advantages of the system described herein have been
achieved. While specific embodiments of the present invention have
been described above, it will be apparent that obvious variations
and modifications of the present invention will occur to those of
ordinary skill in the art from a consideration of the foregoing
description.
[0046] For example, an interconnection for microstrip applications
has been illustrated, but it should be apparent that the inventive
concepts described above would be equally suitable for any
application requiring electrical connections between conductive
traces on two different circuit boards.
[0047] Moreover, many variations in the shape of the printed
circuit pin may be made within the scope of the present
invention.
[0048] It is therefore desired that the present invention be
limited only by the following claims.
* * * * *