1. Field of the Invention
The present application relates to an optical module and a method of assemble the optical module.
2. Background Arts
A conventional optical module provides an optical receptacle to be mated with an external optical connector secured in an end of an optical fiber. Mating the optical connector with the optical receptacle, an optical active device installed within the optical module may optically couple with the optical fiber. However, the optical coupling between the optical connector and the optical receptacle generally requires precise alignment, which inevitably increases a price of the optical module and/or the optical connector.
An optical communication system with small or medium numbers of coupling nodes, for instance, an intercity communication and/or a metro-access system, may install such nodes showing reliable and qualified optical coupling. However, a communication between apparatuses and equipment within a datacenter has a short reach, which eases the condition of the coupling quality, but needs a huge number of nodes. Accordingly, the conventional optical module with the optical receptacle mated with the optical connector brings an excess performance.
A new concept, what is called an active optical cable (hereafter denoted as AOC), has been proposed in the field. The AOC is attached in a tip end of an optical fiber and installs an optical-to-electrical transducer, typically, a semiconductor laser diode (hereafter denoted as LD) and/or a semiconductor photodiode (hereafter denoted as PD). In an AOC, an optical fiber is permanently fixed to, for instance, a housing of the AOC after the optical alignment against the transducer is performed. The AOC converts an optical signal transmitted within the optical fiber into an electrical signal and outputs thus converted electrical signal to a host system through an electrical connector. A Japanese Patent Application published as JP-2012-032574A has disclosed one type of such AOCs. Because the electrical connect or a coupling through an electrical connector does not request a precise alignment between a connector and a plug, which drastically reduces not only a price of the component itself but a cost to assemble the optical module. Moreover, because the transmission distance between nodes in the data center is far shorter, typically several hundred meters at most, the signal quality to be transmitted in optical and electrical forms practically causes no degradation.
A continuous and eager request to make electronic and/or optical apparatus compact has been expanded in the field of the AOC. However, a small-sized electronic connector inevitably accompanies with narrowing a pitch of leads in the connector, which requests a precise control of the alignment between the leads and pads. In particular, when the electrical connector is a type of the double sided connector, further preciseness of the alignment is necessary.
An aspect of the present application relates to an arrangement of an optical module that comprises a substrate and an electronic connector assembled with the substrate. The substrate includes a top surface and a back surface. The top surface provides a plurality of first pads, while, the back surface provides a plurality of second pads. The electronic connector has a plurality of first leads and a plurality of second leads. Each of the first leads and each of the second leads extend along a direction, specifically, a longitudinal direction connecting the substrate to the electronic connector. A feature of the optical module according to an embodiment is that each of the first pads includes a cut opened for the direction and having a left oblique edge and a right oblique edge with a space perpendicular to the direction gradually narrowing along the direction.
The cut typically has a V-shape. When the electronic connector is assembled with the substrate, the first leads of the electronic connector are guided along the V-shaped cut, which automatically and precisely aligns the first leads with the first pads. Even the pitch of the first leads, or the first pads becomes narrower, typically less than 0.6 mm, the misalignment between the first leads and the first pads are effectively prevented.
Another aspect according to an embodiment of the present invention relates to a method to assemble an optical module that provides optical components permanently aligned with optical fibers, electronic components, a substrate that mounts the optical components and the electrical components thereon, and an electronic connector assembled with the substrate. The electronic connector provides a plurality of first leads and a plurality of second leads, while, the substrate provides a plurality of first pads connected to the first leads in the top surface and a plurality of second pads connected to the second leads in the back surface. The method according to an embodiment includes steps of: forming a first solder on the first pads; inserting the substrate into a space between the first leads and the second leads of the electronic connector such that the first leads slide onto the first solder on the first pads; and forming a second solder on the second pads in the back surface of the substrate. A feature of the process is that each of the first pads provides a cut opened for an insertion direction of the substrate, and the cut provides a left oblique edge and a right oblique edge with a space therebetween narrowing along the insertion direction, where each of the first leads is automatically aligned by the cut at the insertion of the substrate.
The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:
Next, some embodiments according to the present application will be described as referring to accompany drawings. In the description of the drawings, elements same with or similar to each other will be referred by numerals or symbols same with or similar to each other without overlapping explanations.
The substrate 2, which has a rectangular plane shape, is a type of a printed circuit board with a width less than 11 mm and a length less than 38 mm, where dimensions of the circuit board are determined by the standard of the optical module. The circuit board 2 includes top and back surfaces, 2a and 2b, to mount electrical components 3 and optical components 4 thereon. The top surface 2a is divided into four areas, 2c to 2f, arranged along the longitudinal direction connecting the front end 2fe to the rear and 2be. In the description below presented, directions of the front, the rear, the top, and the back, are introduced only for the explanation sake, and they do not restrict the scope of the invention. The first to fourth areas, 2c to 2f, mount the optical ferrule 7, the coupling component 6, the electrical components 3, and the electrical connector 5, respectively. The second area 2d provides pads 24 to mount the optical components 4 thereon; and the third area 2f also provides pads 23a to mount the electrical components 3 thereon. The fourth area 2f provides the first pads 21a. These pads, 21a, 23a, and 24, provided in second to fourth areas, 2d to 2f, are formed by electrically conductive metal sheet.
The back surface 2b includes fifth and sixth areas, 2g and 2h, respectively, where two areas, 2g and 2h, are arranged in this order along the longitudinal direction connecting the front end 2fe to the rear end 2be of the substrate 2. The fifth area 2g provides pads 23b to mount the electrical components 3 thereon. The sixth area 2h provides the second pads 21b to mount the electrical connector 5. These pads, 21b and 23b, which will be described in detail later, are made of electrically conductive metal sheet. Moreover, the sixth area 2h in the back surface 2b of the substrate 2 is opposite to the fourth area 2f in the top surface 2a.
The electrical components 3 perform preset sequences for electrical signals converted by the optical components, and output thus processed electrical signals external to the optical module 1 through the electrical connector 5. The electrical components 3 perform another preset sequences for electrical signals provided from an external of the optical module through the electrical connector 5, and provide thus processed electrical signals to the optical components 4. The electrical components 3, which include an integrated circuit (IC) 31, capacitors 32, and so on, are mounted in the second area 2d in the top surface 2a and the fifth area 2g in the back surface 2b. The IC 31 is a type of, for instance, ASIC (application specific integrated circuit) implemented with functions of an optical transmitter and an optical receiver. The embodiment shown in
The optical components 4, which includes an electrical-to-optical transducer 41 (hereafter denoted as E/O device), an optical-to-electrical transducer 42 (hereafter denoted as O/E device), and an IC 43 to driver the E/O device 41 and the O/E device 42, is mounted in the third area 2d of the top surface 2a. The E/O device 41 converts the electrical signals into optical signals and outputs thus converted optical signals to the optical fiber through the coupling component 6. The E/O device may include, for instance, vertical cavity surface emitting laser diodes (VCSELs), where each of the VCSELs corresponds to an optical channel. The O/E device 42, which converts optical signals provided from the optical fiber 12 through the coupling component 6 into electrical signals, may be a plurality of PDs each corresponding to one optical channel. The E/O device 41 and the O/E device 42 of the present embodiment each has an optically active surface facing upward, namely, normal to the top surface of the substrate 2. The embodiment shown in
The IC 43 includes drivers to drive the E/O devices 41 based on electrical signals provided from the electronic components 3 and pre-amplifiers to amplify electrical signals converted from the optical signals and to provide thus amplified electrical signals to the electronic components 3. The AOC 10 generally implements with a plurality of transmitter channels and a plurality of receiver channels; accordingly, the IC 43 installs a plurality of drivers each corresponding to respective transmitter channels and a plurality of pre-amplifiers each corresponding to respective receiver channels. That is, the IC 43 has an arrayed architecture for both of the optical transmitter and the optical receiver.
The electrical connector 5, which is attached to the rear end 2be of the substrate 2, includes a body 51 and a plurality of leads 52. The body 51, which is made of resin or plastic, includes an upper body 51a and a lower body 51b in a rear thereof. The leads 52, which are made of metal pin, extend longitudinally to pierce the body 51. The leads 52 have a width of about 0.2 mm along the lateral direction of the module.
The leads 52 includes a plurality of first leads 52a and a plurality of second leads 52b. The first leads 52a extend along an inner bottom surface of the upper body 51a, pierces the body 51, and extrudes frontward from the body 51; while, the second leads 52b extend along an inner top surface of the lower body 51b, pierces the body 51 and protrudes frontward from the body 51. The first leads 52a in the rear end thereof are warped to protrude toward the lower body 51b, and in the front end thereof are also warped toward the second lead 52b. The second leads 52b in the rear end thereof are warped toward the upper body 51a, and in the front part thereof are also warped toward the first lead 52a. Although not clearly shown in figures, the present embodiment provides ten (10) pairs of the first lead 52a and the second lead 52b. Each of the first leads 52a, or the second leads 52b, makes a pitch to the next lead of 0.6 mm at most. The first lead 52a and the second lead 52b set a space therebetween at each front ends substantially equal to a thickness of the substrate 2.
The coupling component 6 is a member to couple the optical fiber 12 secured in the ferrule 7 optically with the E/O devices 41 and/or the O/E devices 42 mounted on the substrate 2. Specifically, the coupling component 6 is mounted on the second area 2d to cover the optical components 4. The coupling component 6, which is made of resin in the present embodiment, includes a body 61, guide pins 63, and a mirror 64. The body 61, which has a box shape with a center hollow, includes a front wall 61a with two thicker portions 61b in respective sides of the front wall 51a. The guide pins 63 are secured to respective thicker portions 61b and extrude frontward therefrom. The front wall 61a also includes holes 72 corresponding to and facing bores 72 for the optical fibers 12. The mirror 64 is provided in a rear surface of the front wall 61a. The mirror 64 makes an angle of 45° against the top surface 2a of the substrate 2, and a reflecting surface of the mirror faces frontward and downward.
The ferrule 7, which is a type of mechanically transferable (hereafter denoted as MT) in the present embodiment, aligns a plurality of optical fibers 12. The ferrule 7 with a box shape is made of resin and attached to an end of the optical fibers 12. The ferrule 7 provides a depression 71 to support the optical fibers 12 therein, bores 72 each receiving the optical fiber independently, and guide holes 73 formed in both sides of the ferrule 7. Inserting the guide pins 63 into respective guide holes 73, the optical fibers 12 may be optically coupled with the E/O devices 41 and the O/E devices 42 collectively. Light output from the optical fiber 12, which is inserted into the bore of the ferrule 7, passes the bore 72, is reflected by 90° by the mirror 64 toward the substrate 2, and enters the 0/E device 42 mounted on the substrate 2. Or, light output from the E/O device 41 mounted on the substrate 2 upward is reflected by 90° by the mirror 64 toward the ferrule 7, passes the bore 72, and enters the optical fiber 12. The optical fibers 12 constitute the optical cable 11 shown in
The shell 8, which is made of metal, covers and electrically shields the electrical connector 5, in particular, the leads 52 of the electrical connector 5. The shell 8 has dimensions of about 7.4 mm width and about 4.5 mm length. While, the housing 9 of the optical module 1, which may be made of resin with a box shape, has dimensions of about 38 mm longitudinally, about 10.8 mm laterally, and about 7.9 mm in height. The housing 9, which may include an upper housing 91 and a lower housing 92, provides an opening 9a in the front end thereof, while another opening 9b in the rear end. The housing 9 encloses the substrate 2, the electronic components 3, the optical components 4, the coupling component 6, and the ferrule 7. The electrical connector 5 and the shell 8 extend from the latter opening 9b, while, the optical cable 11 is pulled out from the other opening 9a.
The fourth area 2f in the top surface 2a of the substrate 2 and the sixth are 2h in the back surface 2b thereof will be described in detail. As shown in
The sixth area 2h has a configuration substantially same with those of the fourth area 4f; that is, the sixth area 2h also provides a plurality of second pads 21b each having a shape substantially same with those of the first pads 21a. The second pads 21b are laterally arranged by a pitch less than 0.6 mm. The embodiment shown in
Each of the pads 21 includes a left edge 21c and a right edge 21d both extending longitudinally. Rear end of each of the pads 21 provides a cut 211 cut from the rear end of the left 21c and that of the right 21d forwardly. The cut 211 provides a left oblique edge 21e and a right oblique edge 21f. The left oblique edge 21e extends from the left edge 21c toward a center of the pad 21, while, the right oblique edge 21f extends from the right edge 21d toward the center. Because of the V-shape of the cut 211, a lateral space between the left oblique edge 21e and the right oblique edge 21f gradually narrows from the rear end thereof toward the deep end of the cut 211. The left oblique edge 21e and the right oblique edge 21f become substantially symmetry with respect to a longitudinal center of the pad 21, and make an angle of θ. That is, the cut 211 is a V-shaped cut with an angle of θ, where the angle θ may be, for instance, 90°.
The pad 21 is covered by solder 25 with a shape substantially tracing the shape of the pad 21 and a preset thickness. The solder 25 on a rear end of the pad 21 forms a guide that enables to guide terminals 52 inserted from the rear end 2be of the substrate 2. The embodiment shown in
Next, a process to assemble the optical module 1 will be described.
The preparation of the substrate S01, as shown in
Then, the process S03, as shown in
The process S04, as shown in
Then, the process S05 installs the coupling component 6 in the second area 2d of the top surface 2a, as shown in
The process S07, as shown in
Subsequently, step S14 prints solder pastes on the pads, 21b and 23b, in the back surface 2b, then, other electrical components 3 are placed on the solder paste on the pads, 21b and 23b. After applying flux on the first solder 25a on the first pad 21a in the top surface 2a, the electrical connector 5 is set on the substrate 2 from the rear end 2be thereof at step S16 such that the first leads 52a slide onto the first pads 21a and the second leads 52b slide onto the second pads 21b. At this process, the V-shaped cut 211 of the pads 21 may guide the leads 52 to align them on a respective center of the pads 21. The first leads 52a are aligned on the first pads 21a and the second leads 52b are aligned on the second pads 21b.
Describing the process further specifically, when the leads 52 of the electrical connector 5 is set forward from the rear end 2be of the substrate 2, the first and second leads, 52a and 52b, in the front warped portions thereof slide on the top and back surfaces, 2a and 2b, because the front warped portions are apart by a space substantially equal to the thickness of the substrate 2, and the end of respective leads, 52a and 52b, reach the end of pads, 21a and 21b. Because the width of the pad 21, namely space between the left oblique edge 21e and the right oblique edge 21f at the rear end of the V-shaped cut 211, is greater than a width of the terminal 52, the tip end of the leads 52 are aligned between two oblique edges, 21e and 21f. As the space between two oblique edges, 21e and 21f, decreases as the leads 52 moves forward, the tip of the leads 52 comes in contact with one of two oblique edges, 21e and 21f. Further sliding the leads forward, a left side of the lead 52 comes in contact with the first solder 25 along the left oblique edge 21e and a right side thereof comes in contact with the first solder 25 along the right oblique edge 21f. Thus, the leads 52, namely, the upper and second leads, 52a and 52b, are adequately positioned on the substrate 2.
Further inserting the substrate 2 between two leads, 52a and 52b, the two leads, 52a and 52b, ride up onto the solder 25. Thus, the leads 52 may be smoothly rid up onto the pads, 21a and 21b, as laterally positioned with respect to respective pads, 21a and 21b; accordingly, the alignment of the leads 52 with respect to the pads 21 of the substrate 2 may be enhanced. Moreover, because the space between two oblique edges, 21e and 21f, at the open end of the pad 21 is wider than the width of the leads 52, the end of the pads 21 is not peeled at the insertion of the leads 52 to the substrate 2.
After the insertion of the leads 52, the reflow soldering not only mounts the electronic components 3 on the back surface 2b but assembles the electrical connector 5 with the substrate 2. Specifically, a temperature condition of 260° C. for 1 minute melts the solder paste on the back surface 2b and the first solder 25a on the first pads 21a and a subsequent process to cool down to a room temperature solidifies the solder to fix the electronic components 3 to the pads 23b and two leads, 52a and 52b, to the first and second pads, 21a and 21b, respectively.
On the other hand, the pad 21 of the embodiment provides the V-shaped cut 211 with two oblique edges, 21e and 21f. The first solder 25a applied on the first pad 21a has the plane shape tracing the shape of the first pad 21a and the substantial thickness. Inserting the electrical connector 5 into the substrate 2 from the rear end 2be thereof after the first solder 25a is formed on the first pad 21a; the leads 52 of the electrical connector 5 are automatically positioned by the first solder 25a provided along two oblique edges, 21e and 21f. Because two oblique edges, 21e and 21f, gradually decrease the space therebetween as the tip of the leads 52 is apart from the rear end 2be of the substrate 2; the tip of the leads 52 may slide onto the first solder 25a without peeling the pads 21a. Thus, the lateral position of the leads 52 along the width of the first pads 21a is automatically aligned with respect to the first pads 21a. The present embodiment is able to align the leads 52 of the electrical connector 5 with the first pads 21 on the substrate 2 even one of the surfaces, 2a and 2b, is not inspected.
The pads 21 on the substrate of the present embodiment have the width less than 0.3 mm and the pitch less than 0.6 mm. When the pad 21 provides a rectangular cut, in other words, a U-shaped cut, a width of side patterns putting a space therebetween of the U-shape becomes narrower, which easily causes a peeling-off the pattern from the substrate 2 when the leads 52 scribe edges of the pattern during the insertion. The V-shaped cut of the embodiment leaves a substantial width of the side patterns at positions apart from the edge thereof; accordingly, the tolerance to the peeling-off may be enhanced. Thus, the optical module 1 of the embodiment effectively avoids the misalignment between the terminals 52 of the electrical connector 4 and the pads 21 on the substrate 2.
The optical module and the assembling method thereof are not restricted to embodiments described above. For instance,
Then, applying fluxes on the first solder 25a on the first pads 21a and the second solder 25b on the second pads 21b, the electrical connector 5 is inserted forward into the substrate 2 from the rear end 2be thereof such that the first leads 52a is placed on the first pads 21a and the second leads 52b is on the second pads 21b. The V-shaped cut of the pads, 21a and 21b, guides the first and second leads, 52a and 52b, and aligns the first and second leads, 52a and 52b, with the pads, 21a and 21b. Subsequent reflow soldering, the third reflow soldering, fixes the electrical connector 5 with the substrate 2 at step S28. The soldering conditions of the temperature of 260° C. for one minute melts the first and second solder, 25a and 25b, each formed on the first and second pads, 21a and 21b, and the subsequent cooling down solidifies the first and second solders, 25a and 25b, to fix the first and second leads, 52a and 52b, to the first and second pads, 21a and 21b.
The embodiments described above provides the V-shaped cut in both of the first and second pads, 21a and 21b, or pads 21 formed on both of the top and back surfaces, 2a and 2b, of the substrate 2. However, another embodiment of the substrate 2, where only one of the pads, 21a and 21b, provide the V-shaped cut and other of the pads, 21b and 21a, provide no V-shaped cut, is applicable. The inspection to check the positional relation between the pads and the terminals is performed for a side of the surfaces, 2a and 2b, where no V-shaped cut is formed in the pads, while, the pads in the other surface, 2b and 2a, automatically position the terminals by the V-shaped cut.
Although the embodiments described above concentrates the pad 21 having the V-shaped cut 211, the pad may have an alteration as shown in
Accordingly, the present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
Number | Date | Country | Kind |
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2012-219429 | Oct 2012 | JP | national |