U.S. patent application number 11/240400 was filed with the patent office on 2007-04-05 for simple fiducial marking for quality verification of high density circuit board connectors.
This patent application is currently assigned to Emcore Corporation. Invention is credited to Thomas Whitehead.
Application Number | 20070077011 11/240400 |
Document ID | / |
Family ID | 37902038 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070077011 |
Kind Code |
A1 |
Whitehead; Thomas |
April 5, 2007 |
Simple fiducial marking for quality verification of high density
circuit board connectors
Abstract
A printed circuit board with a printed pattern of fiducial marks
on a first side of the printed circuit board including a first
indicia including a right triangle with its base parallel to a
first edge of the board and an alignment mark adjacent thereto, and
a second indicia including a right triangle with its base parallel
to a second edge of the board opposite said first edge, and an
alignment mark adjacent thereto.
Inventors: |
Whitehead; Thomas; (Chicago,
IL) |
Correspondence
Address: |
Emcore Corporation
1600 Eubank Blvd SE
Albuquerque
NM
87123
US
|
Assignee: |
Emcore Corporation
|
Family ID: |
37902038 |
Appl. No.: |
11/240400 |
Filed: |
September 30, 2005 |
Current U.S.
Class: |
385/88 ;
385/92 |
Current CPC
Class: |
H05K 3/0052 20130101;
G02B 6/4201 20130101; G02B 6/428 20130101; H05K 1/0269 20130101;
H05K 1/117 20130101; G02B 6/4246 20130101; H05K 2203/163 20130101;
G02B 6/4284 20130101 |
Class at
Publication: |
385/088 ;
385/092 |
International
Class: |
G02B 6/36 20060101
G02B006/36 |
Claims
1. A printed circuit board comprising: a printed pattern of
fiducial marks on a first side of the printed circuit board
including a first indicia including a right triangle with its base
parallel and adjacent to a first edge of the board and an alignment
mark adjacent thereto, and a second indicia including a right
triangle with its base parallel and adjacent to a second edge of
the board opposite said first edge, and an alignment mark adjacent
thereto.
2. A printed circuit board as defined in claim 1, further
comprising a plurality of connector contact areas extending along a
third edge of said board between said first edge and said second
edge.
3. A printed circuit board as defined in claim 2, wherein the
alignment mark has an edge adjacent said right triangle extending
substantially parallel to the edge of the board, with the right
triangle disposed between the alignment mark and the respective
edge of the board.
4. A planar printed circuit board having a first edge, a second
edge opposite said first edge, and a third edge extending between
said first and second edge; and a printed circuit pattern imprinted
on a first side of said circuit board using a mask pattern
including a plurality of connector contact areas extending along
said third edge and a first indicia including a right triangle with
its base parallel and adjacent to a first edge of the board and an
alignment mark adjacent thereto, and a second indicia including a
right triangle with its base parallel and adjacent to a second edge
of the board opposite said first edge, and an alignment mark
adjacent thereto.
5. A planar printed circuit board as defined in claim 4, wherein
the printed circuit pattern has a predetermined specified width
between said first and second edge, and a portion of at least one
of the right triangles extends on the mask beyond said specified
width so that an optimally dimensional circuit board has a
truncated right triangle imprinted upon it.
6. A planar printed circuit board as defined in claim 5, wherein
the specification for a properly printed and routed board has the
apex of each right triangle disposed between the upper and lower
edges of the adjacent alignment mark.
7. An optical transceiver for converting and coupling an
information-containing electrical signal with an optical fiber
comprising: a housing including a fiber optic connect adapted for
coupling with an external optical fiber for transmitting and/or
receiving an optical communications signal; a rigid printed circuit
board in the housing including an edge forming a connector for
coupling with an external electrical cable or information system
device and for transmitting and/or receiving an
information-containing electrical communications signal; and a
first indicia including a right triangle with its base parallel and
adjacent to a first edge of the board and an alignment mark
adjacent thereto, and a second indicia including a right triangle
with its base parallel and adjacent to a second edge of the board
opposite said first edge, and an alignment mark adjacent thereto,
for assuring the accuracy and alignment of the electrical contacts
of the connector.
8. An optical transceiver as defined in claim 7, further comprising
a plurality of connector contact areas extending along a third edge
of said board between said first and second opposed edges.
9. A transceiver as defined in claim 7, wherein the printed circuit
board is printed using a mask with a pattern of fiducial marks with
a predetermined specified distance to the ideal or optimum location
of said first and second edge, and the right triangle indicia
fiducial mark extends on the mask beyond said specified board width
so that an optimally dimensional circuit board has smaller right
triangles imprinted upon it than the right triangle indicia on the
mask.
10. A transceiver as defined in claim 7, wherein the specification
for a properly printed and routed board has the apex of each right
triangle disposed between the upper and lower edges of the adjacent
alignment mark.
11. A method of qualifying the accuracy of a printed circuit board
comprising: providing a printing mask pattern for a first side of
the printed circuit board with a first spaced indicia including a
right triangle with its base parallel and adjacent to a first edge
of the board; and a second spaced indicia including a right
triangle with its base parallel and adjacent to a second edge of
the board opposite said first edge; printing a layer of visually
conspicuous material on a printed circuit board using said mask
pattern; determining the position of the apex of one indicia with
respect to a corresponding alignment mark on the printed circuit
board; and based upon such position against a qualification
criteria, accepting or rejecting the board.
12. A method as defined in claim 11, wherein a plurality of boards
are implemented on a panel and further comprising separating the
board from the panel prior to the determining step.
13. A method as defined in claim 11, wherein the method of
separating includes routing.
14. A method as defined in claim 11, wherein the determining step
is performed by visual inspection of the first and second sides of
the board by an operator.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to copending U.S. application
Ser. No. ______, of Lau et al. filed simultaneously herewith.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to electro-optic conversion modules,
and particularly to the use of fiducial markings on such printed
boards in such modules for verification of printing alignment,
fabrication accuracy, and quality control of printed electrical
connectors fabricated on such boards.
[0004] 2. Description of the Related Art
[0005] Optical data transmission networks provide high capacity
signal transmission without many of the physical limitations of
electrical cables. Fiber-optic transceivers used in such networks
convert electrical signals into optical signals and vice versa at
the interface of a fiber-optic cable and an electronic network
unit, such as a computer or communications system.
[0006] To extend the application of the fiber optic transceiver for
mass-produced, low-cost computer and communications devices, it is
desirable for the individual components to be economical to
fabricate, and thus the electrical connect to be simple and
reliable at the same time. The typical hardware design of these
low-cost transceivers provides the use of a printed circuit board
that terminate on one side with a cut out pin edge or a contact
array forming a multi-pin electrical connector, which may be
implemented on one or both sides of the board. With such a contact
array, the circuit board can be directly plugged into a mating
electrical receptacle on the back end of the chassis of a host
computer. The cut out connector may also be elongated, and sized to
be able to extend through an open slot in the back face of the
computer chassis so that connection may be made to a receptacle
mounted inside the chassis on a mother board of the computer.
[0007] A number of industry standards have been defined to
integrate some of these electrical connector design considerations
into opto-electronic transceiver modules. For example, the XENPAK
standard (see www.xenpak.org) describes an advantageous
opto-electronic transceiver module package with a cut out printed
circuit board electrical connector.
[0008] Like any lithographically printed circuit board, mask
alignment and routing introduce variations from board to board that
present issues of reliability and quality control, especially for
high density pin configuration.
[0009] Prior to the present invention, there has not been a
reliable process to ensure quality control in parallel optical
module with a cut-out printed pin array electrical connector. Thus,
it is desired to have a fiducial mark associated with the board
design for the pin out or electrical contact array for making the
electrical connection from the board which can be quickly and
easily visually checked by quality assurance personnel in a
production environment to determine if the routed board meets
specification.
SUMMARY OF THE INVENTION
[0010] Briefly and in general terms, the present invention provides
printed circuit board having a printed pattern of fiducial marks on
a first side of the printed circuit board including a first indicia
including a right triangle with its base parallel to a first edge
of the board and an alignment mark adjacent thereto, and a second
indicia including a right triangle with its base parallel to a
second edge of the board opposite said first edge, and an alignment
mark adjacent thereto.
[0011] In another aspect, the invention further provides planar
printed circuit board having a first edge, a second edge opposite
the first edge, and a third edge extending between the first and
second edge; and a printed circuit pattern imprinted on a first
side of the circuit board using a mask pattern including a
plurality of connector contact areas extending along the third edge
and a first indicia including a right triangle with its longer side
parallel to a first edge of the printed circuit board.
[0012] In a further aspect, the present invention provides an
optical transceiver for converting and coupling an
information-containing electrical signal with an optical fiber
having a housing including a fiber optic connector adapted for
coupling with an external optical fiber for transmitting and/or
receiving an optical communications signal; a rigid printed circuit
board in the housing including a first edge forming a connector for
coupling with an external electrical cable or information system
device and for transmitting and/or receiving an
information-containing electrical communications signal; and a
pattern of triangular shaped fiducial marks on second and third
opposed edges of said circuit board for assuring the accuracy and
alignment of the electrical contacts of said connector.
[0013] In another aspect, the invention provides a method of
qualifying the accuracy of a printed and cut printed circuit board
by providing a printing mask pattern for a first side of the
printed circuit board with a first sequence of a spaced indicia
adjacent to a first edge of the board; and a second sequence of
spaced indicia adjacent to a second edge of the board opposite said
first edge; printing a layer of visually conspicuous material on a
printed circuit board using said mask pattern; determining position
of the acute angle vertex of the triangle with respect to the
alignment mark and based upon such determination accepting or
rejecting the board.
[0014] In still another aspect, the invention provides a method of
increasing the accuracy of a quality control screening procedure by
providing an alignment guide that magnifies the measurement of a
potential error by a factor depending upon the angle of the apex of
the triangle fiducial mark. The measured distance is effectively
mirrored and amplified across the hypotenuse of the right triangle.
The degree of magnification is controlled by the acute angle of the
triangle fiducial. This feature increases the accuracy of the
measurement of a routing error and enables visual inspection of the
production boards.
[0015] The novel features and characteristics of the invention are
set forth in the appended claims. The invention itself, however, as
well as other features and advantages thereof, will be best
understood by reference to a detailed description of a specific
embodiment, when read in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an exploded perspective view of an optical
transceiver incorporating the cut out printed circuit board
according to the present invention;
[0017] FIG. 2 is the mark pattern of fiducial indicia used for
printing a printed circuit board according to the present
invention;
[0018] FIG. 3a depicts a production printed circuit board with a
pattern of fiducial indicia present after routing;
[0019] FIG. 3b is an enlarged view of the left fiducial markings of
the board of FIG. 3a;
[0020] FIG. 4 is an alternative mark pattern of fiducial indicia
according to the present invention; and
[0021] FIG. 5 is a flow chart depicting the method of using the
fiducial marks according to the present invention in a quality
control protocol.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] Details of the present invention will now be described,
including exemplary aspects and embodiments thereof. Referring to
the drawings and the following description, like reference numbers
are used to identify like or functionally similar elements, and are
intended to illustrate major features of exemplary embodiments in a
highly simplified diagrammatic manner. Moreover, the drawings are
not intended to depict every feature of actual embodiments or the
relative dimensions of the depicted elements, and are not drawn to
scale.
[0023] FIG. 1 is an exploded perspective view of an optical
transceiver 100 incorporating the cut out printed circuit board
with fiducial marks according to the present invention. In this
particular embodiment, the transceiver 100 is compliant with the
IEEE 802.3ae 10 GBASE-LX4 Physical Media Dependent sub-layer (PMD)
and the XENPAK.TM. form factor. It is to be noted, however, that
the transceiver 100 may be configured to operate under various
other compliant protocols (such a Fibre Channel or SONET) and be
manufactured in various alternate form factors such as X2. The
transceiver 100 is preferably a 10 Gigabit Coarse Wavelength
Division Multiplexed (CWDM) transceiver having four 3.125 Gbps
distributed feedback lasers and provides 300 meter transmission
over legacy installed multimode fiber and from 10 to 40 km over
standard single mode fiber.
[0024] The transceiver 100 includes a two-piece housing 102 with a
base 104 and a cover 106. In addition, contact strips 152 are
provided to ground the module to chassis ground as well. The
housing 102 is constructed of die-cast or milled metal, preferably
die-cast zinc, although other materials also may be used, such a
specialty plastics and the like. Preferably, the particular
material used in the housing construction assists in reducing EMI.
Further, EMI reduction may be achieved by using castellations (not
shown) formed along the edges of the housing 102.
[0025] The front end of the transceiver 100 includes a faceplate
132 for securing a pair of receptacles 124, 126. The receptacles
124, 126 are configured to receive fiber optic connector plugs 128,
130. In the preferred embodiment, the connector receptacle 128, 130
are configured to receive an optical fiber with industry standard
SC duplex connectors (not shown). As such, keying channels 132 and
134 are provided to ensure that the SC connectors are inserted in
their correct orientation. Further, as shown in the exemplary
embodiment and discussed further herein, the connector receptacle
126 receives an SC transmitting connector and the connector plug
124 receives an SC receiver connector.
[0026] In particular, the transceiver housing holds one or more
circuit boards, including a transmit receive and a physical coding
sub-layer subassemblies, and interface board 112, which is used to
provide an electrical interface to external electrical systems (not
shown).
[0027] The rear edge 113 of the board 112 includes a printed
pattern of contact points 114 which form individual electrical
connections to an external mating receptacle on the external system
which the transceiver is associate with. The size and number of
pins depends upon the particular standard. In the preferred
embodiment, the 70 pin board edge connector is as set forth in the
XENPAK and X2 Multi-Source Agreements.
[0028] FIG. 2 is the mark pattern of fiducial indicia 201 and 202,
and 203 and 204 used in a mask for printing a single printed
circuit board according to the present invention. In an actual
production process, a number of identical printed circuit boards
will be laid out in an array on a panel and printed simultaneously.
After the single panel is printed, the individual boards are then
separated or cut out with a router or other process equipment.
[0029] FIG. 3(a) depicts the result of an overlay of the mark
pattern of FIG. 2 over a printed circuit board 200 which is printed
with metallization, including the contact points 114, and routed.
The result of the routing creates a different sizing of the
original fiducial marks.
[0030] In particular, the figure depicts the top view of a specimen
production printed circuit after routing illustrating a resulting
fiducial mark pattern that may be used by the technique of the
present invention for quality control inspection. Because of the
position of the left hand edge 305 at the board, as determined by
the router, the left side right triangle 301 has been approximately
cut in half, with the vertex 400 now located at substantially the
same distance from the rear edge 113 as the left hand side 401 of
the fiducial mark 302.
[0031] On the other edge 306 of the board 112, the right triangle
303 has been barely cut or diminished by the router. The vertex 402
of triangle 303 lies well below the right hand side 403 of the
fiducial mark 304, as is apparent from visual inspection.
[0032] The present invention utilizes the position of the vertex of
the right triangle with respect to the alignment edge 401 or 403 of
the alignment mark to determine whether the board is acceptable.
FIG. 3(b) is an enlarged view of the left side of the printed
circuit board illustrated in FIG. 3(a) to more accurately describe
the acceptability criteria. The quality control operator notes the
position of the vertex 400 of the triangular fiducial mark 301 as
determined by the cut 305 that forms the left hand peripheral edge
of the board. One then considers an imaginary line 503 parallel
with the rear edge 113 originating at the vertex 400 and extending
into the adjacent rectangular-shaped alignment fiducial mark 302.
If the line 503 intersect the mark 302, i.e. the line lies between
the upper corner edge 500 and the lower corner edge 501 of the left
hand peripheral side of the mark 302, then the routing cut 305 is
within specification.
[0033] Of course, fiducial marks other than right triangles and
rectangular-shaped alignment fiducial marks may be used as well,
and are within the scope of the present invention.
[0034] FIG. 4 is an alternative fiducial mark pattern according to
the present invention. The alignment marks 601 and 603 are
identical as 302 and 304 in FIG. 3(a). The right triangles 600 and
602 are similar in size as 301 and 303 in FIG. 3(a), but are
oriented differently. Instead of the lower vertex 400 being used as
in FIG. 3(a), the embodiment of FIG. 4 utilizes the upper vertex
604, as the point to be compared with the adjacent peripheral edge
of the alignment mark 601.
[0035] FIG. 5 is a flow chart depicting the method of using the
fiducial marks according to the present invention in a quality
control protocol. In the highly simplified method illustrated in
the flow chart, the first step 701 is to provide a mask pattern
with fiducial marks including a right triangle shaped indicia, and
a corresponding alignment mark, associated with the edge where the
pin contacts are to be printed.
[0036] In the next step 702, a layer is printed on the printed
circuit board (or on the panel of several boards) including the
fiducial marks. Typically, the fiducial marks may be the same metal
layer as the pin contacts, so only a single print step is involved
for each side of the board. Following printing, the individual
boards may be separated or routed from the panel.
[0037] The next step 703 is to determine the location of the apex
of the indicia with respect to an alignment mark on the first and
second opposite edges of the board, on each side, and to utilize
that information in the next step 704 to compare the result to a
predetermined selection criteria to qualify the board.
[0038] More particularly, the present invention can be described as
a method of qualifying the accuracy of a printed circuit board by
providing a printing mask pattern for a first side of the printed
circuit board with a first sequence of a spaced indicia parallel to
a first edge of the board; and a second sequence of spaced indicia
parallel to a second edge of the board opposite said first edge. A
layer of visually conspicuous material (such as the metallization
pattern) is then printed on the printed circuit board using said
mask pattern. The individual boards are then cut or routed from the
panel on which they were printed, and the quality inspection
process according to the present invention can be commenced. A
human operator can visually inspect the board and determine if the
board has been accurately routed by examining the right triangles
printed on the first and second edges respectively of the board.
This data can then be compared against a qualification criteria to
accept or reject the board.
[0039] It will be understood that each of the elements described
above, or two or more together, also may find a useful application
in other types of constructions differing from the types described
above.
[0040] While the invention has been illustrated and described as
embodied in a quality control method for printed circuit boards, it
is not intended to be limited to the details shown, since various
modifications and structural changes may be made without departing
in any way from the spirit of the present invention.
[0041] Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior art,
fairly constitute essential characteristics of the generic or
specific aspects of this invention and, therefore, such adaptations
should and are intended to be comprehended within the meaning and
range of equivalence of the following claims.
* * * * *
References