Socketless land grid array

Abstract

A socketless land grid array (LGA) is provided that uses an adhesive material rather than a socket to secure the optical communications module to the LGA and to provide the clamping force that is needed to maintain contact between the module and the LGA and to maintain a flat profile for the module and the LGA. Eliminating the LGA socket eliminates the need to drill holes in the host circuit board and the need for additional hardware (e.g., backing plates, screws, etc.) to secure a socket to the host circuit board. This allows the area of the host circuit board underneath the array of electrical contacts of the LGA to be used for routing electrically-conductive pathways of the host circuit board (e.g., vias and traces) and reduces the amount of time and effort that are needed to secure modules to the respective LGAs.

Claims

1. A socketless land grid array (LGA) comprising: a first mounting region of a first surface of a first host circuit board (CB); a first array of electrical contacts disposed on the first surface of the first host CB in the first mounting region; a first module mounted in the first mounting region, the first module having a first module CB, the first module CB having a second array of electrical contacts disposed on a first surface thereof, wherein the electrical contacts of the second array are in contact with respective electrical contacts of the first array; passive alignment features on the first host CB and on the first module for passively aligning the first module with the first host CB to thereby align the electrical contacts of the first array with the respective electrical contacts of the second array when the first module is mounted in the first mounting region; and a first amount of non-electrically-conductive adhesive material disposed on the first surface of the first host CB in the first mounting region and on the first surface of the first module CB, wherein the first amount of adhesive material secures the respective electrical contacts of the first and second arrays to one another and secures the first surface of the first host CB to the first surface of the first module CB.

2. The socketless LGA of claim 1, wherein the first amount of adhesive material is in contact with the first array of electrical contacts.

3. The socketless LGA of claim 1, wherein the non-electrically-conductive adhesive material is epoxy.

4. The socketless LGA of claim 1, wherein the non-electrically-conductive adhesive material is glue.

5. The socketless LGA of claim 1, wherein the first module is a first parallel optical communications module.

6. The socketless LGA of claim 1, wherein the passive alignment features include at least first and second frame members of the first host CB that at least partially define the first mounting region and that come into contact with first and second sides, respectively, of the first module CB when the first module is mounted in the first mounting region.

7. The socketless LGA of claim 1, wherein the passive alignment features include at least first, second and third frame members of the first host CB that at least partially define the first mounting region and that come into contact with first, second and third sides, respectively, of the first module CB when the first module is mounted in the first mounting region.

8. The socketless LGA of claim 1, wherein the passive alignment features include at least a first male feature of the first host CB and at least a first complementarily-shaped and sized female feature of the first module CB that engage one another when the first module is mounted in the first mounting region.

9. The socketless LGA of claim 1, wherein the passive alignment features include at least a first and second males feature of the first host CB and at least a first and second complementarily-shaped and sized female features of the first module CB that engage one another, respectively, when the first module is mounted in the first mounting region.

10. The socketless LGA of claim 1, wherein the passive alignment features include at least a first male feature of the first module CB and at least a first complementarily-shaped and sized female feature of the first host CB that engage one another when the first module is mounted in the first mounting region.

11. The socketless LGA of claim 1, wherein the passive alignment features include at least a first and second males feature of the first module CB and at least a first and second complementarily-shaped and sized female features of the first host CB that engage one another, respectively, when the first module is mounted in the first mounting region.

12. The socketless LGA of claim 1, wherein the first host CB has at least a first active alignment feature for actively aligning the first module with the first host CB to thereby align the electrical contacts of the first array with the respective electrical contacts of the second array when the first module is mounted in the first mounting region.

13. The socketless LGA of claim 1, wherein the first module CB has a through hole formed through it for allowing the first amount of non-electrically-conductive adhesive material to be dispensed through the through hole into a space that exists between the first surface of the first module CB and the first surface of the first host CB.

14. An electrical interface for interfacing module circuit boards (CBs) with host CBs, the electrical interface comprising: a plurality of mounting regions of a first surface of a first host CB; a plurality of first arrays of electrical contacts disposed on the first surface of the first host CB in the respective mounting regions; a plurality of first modules mounted in the respective mounting regions, each of the first modules having a first module CB having a second array of electrical contacts disposed on a first surface of the first module CB, wherein the electrical contacts of each of the first arrays are in contact with respective electrical contacts of a respective one of the second arrays; passive alignment features on the first host CB and on the first modules for passively aligning the first modules with the respective mounting regions of the first host CB to thereby align the electrical contacts of the first array with the respective electrical contacts of the second array when the first modules are mounted in the respective mounting regions; and first amounts of non-electrically-conductive adhesive material disposed on the electrical contacts of the first and second arrays and securing the electrical contacts of the first array to the respective electrical contacts of the respective second array, and wherein the first amounts of non-electrically-conductive adhesive material are in contact with the first surfaces of the first host CB and of the first module CBs and secure the first module CBs to the first host CB in the respective mounting regions.

15. The electrical interface of claim 14, wherein the passive alignment features include frame members of the first host CB that at least partially define the mounting regions and that come into contact with sides of the respective first module CBs when the first modules are mounted in the respective mounting regions.

16. The electrical interface of claim 14, wherein the passive alignment features include male features of the first host CB and complementarily-shaped and sized female features of each of the first module CBs that engage one another when the first modules are mounted in the respective mounting regions.

17. The electrical interface of claim 14, wherein the first host CB has active alignment features for actively aligning the first modules with the respective mounting regions to thereby align the electrical contacts of the first arrays with the respective electrical contacts of the second arrays when the first modules are mounted in the respective mounting regions.

18. The electrical interface of claim 14, wherein the first module CBs have respective through holes formed through them for allowing the first amounts of non-electrically-conductive adhesive material to be dispensed through the through holes into spaces that exist between the first surfaces of the first module CBs and the first surface of the first host CB.

19. A socketless land grid array (LGA) comprising: a first mounting region of a first surface of a first host circuit board (CB); a first array of electrical contacts disposed on the first surface of the first host CB in the first mounting region; a first module mounted in the first mounting region, the first module having a first module CB, the first module CB having a second array of electrical contacts disposed on a first surface thereof, wherein the electrical contacts of the second array are in contact with respective electrical contacts of the first array; at least a first active alignment feature on the first host CB for actively aligning the first module with the first host CB to thereby align the electrical contacts of the first array with the respective electrical contacts of the second array when the first module is mounted in the first mounting region; and a first amount of non-electrically-conductive adhesive material disposed on the first surface of the first host CB in the first mounting region and in contact with the first array of electrical contacts, and wherein the first amount of adhesive material secures the respective electrical contacts of the first and second arrays to one another and secures the first surface of the first host CB to the first surface of the first module CB.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a top perspective view of a PCI card having a host circuit board that has a plurality of mounting areas for mounting respective parallel optical communications modules thereon.

(2) FIG. 2 illustrates an enlarged top perspective view of the portion of the PCI card shown in the dashed circle labeled with reference numeral 8 in FIG. 1, except that the portion of the PCI card shown in FIG. 2 has a plurality of parallel optical communications modules mounted thereon in the respective mounting areas.

(3) FIGS. 3A and 3B illustrate top and bottom perspective views, respectively, of one of the parallel optical communications modules shown in FIG. 2.

(4) FIG. 4A illustrates a cross-sectional perspective view of the portion of the mounted configuration of the module and its respective LGA contained in the dashed circle labeled with reference numeral 18 in FIG. 2 and taken along dashed line A-A′ in FIG. 2.

(5) FIG. 4B illustrates an enlarged view of the portion of the mounted configuration of the module and its respective LGA contained in dashed circle labeled with reference numeral 19 in FIG. 4A.

(6) FIG. 5 illustrates a top view of a portion of a host circuit board of a parallel optical communications module having a plurality of socketless LGAs formed thereon in accordance with another illustrative embodiment.

(7) FIG. 6 illustrates a top view of the socketless LGAs shown in FIG. 5 with respective module circuit boards mounted on them.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

(8) In accordance with the invention, a socketless LGA is provided that uses an adhesive material rather than a socket to secure an optical communications module to the LGA. The adhesive bond provides the clamping force that is needed to maintain contact between the module and the LGA and that is needed to maintain a flat profile for the mounted configuration of the module on the LGA. Eliminating the LGA socket eliminates the need to drill holes in the host circuit board and the need for additional hardware (e.g., backing plates, screws, etc.) to secure a socket to the host circuit board. This allows the area of the host circuit board underneath the array of electrical contacts of the LGA to be used for routing electrically-conductive pathways of the host circuit board (e.g., vias and traces), reduces the amount of time and effort that are needed to secure modules to the respective LGAs, and reduces the final solution size both within the plane of the host circuit board and in total thickness.

(9) An illustrative, or exemplary, embodiment of the socketless LGA and the manner in which it may be used with a parallel optical communications module will now be described with reference to the FIGS. 1-6, in which like reference numerals represent like elements, components or features. It should be noted that features in the figures are not necessarily drawn to scale, emphasis instead being placed on demonstrating principles and concepts of the invention.

(10) The term “circuit board,” or CB, as those terms are used herein, are intended to denote any circuit board, including, but not limited to, a PCB, a flex circuit, or any other substrate having electrical conductors routed through it on which the socketless LGA may be formed. The term “parallel optical communications module,” as that term is used herein, is intended to denote any one of a parallel optical transceiver module, a parallel optical receiver module, or a parallel optical transmitter module.

(11) For illustrative, or exemplary purposes, the socketless LGA will be described as being used with a Peripheral Component Interconnect (PCI) card having a plurality of parallel optical communications modules mounted on it that are interconnected with other system modules when the PCI card is plugged into a PCI slot. The PCI card is merely an example of one possible implementation scenario for the socketless LGA and is intended to demonstrate one of a virtually infinite number of possible applications for the socketless LGA.

(12) FIG. 1 illustrates a top perspective view of a PCI card 1 having a host CB 2 that has a plurality of mounting areas 3 for mounting respective parallel optical communications modules (not shown) thereon. The PCI card 1 has cylindrical pins 4 on opposite sides of a forward end thereof for mating with respective bores (not shown) of a PCI slot (not shown). In accordance with this illustrative embodiment, each mounting area 3 is surrounded on three sides by frame members 3a-3c of the PCI card 1. Each mounting area 3 of the host CB 1 has an array of electrical contacts 5 thereon that, together with the portions of the CB 2 within the mounting areas 3 and the adhesive material (not shown), comprise the socketless LGA 10, as will be described below in more detail. The adhesive material is a non-electrically-conductive adhesive material so that it does not create a short circuit between neighboring electrical contacts 5. The frame member 3a of each of the mounting areas 3 is part of a larger frame 6 of the PCI card 1 that, along with fastening members 7, holds the host CB 2 in position on the PCI card 1. The frame 6 is typically made of a hard plastic material, although other materials may be used for this purpose.

(13) FIG. 2 illustrates an enlarged top perspective view of the portion of the PCI card 1 shown in the dashed circle labeled with reference numeral 8 in FIG. 1, except that the portion of the PCI card 1 shown in FIG. 2 has a plurality of parallel optical communications modules 11 mounted thereon in the respective mounting areas 3. In FIG. 2, one of the parallel optical communications modules 11 is positioned above its respective mounting area 3 as it is about to be mounted on the respective LGA 10. FIGS. 3A and 3B illustrate top and bottom perspective views, respectively, of one of the parallel optical communications modules 11 shown in FIG. 2. As shown in FIG. 3B, the module 11 has an array of electrical contacts 12 disposed on a lower surface 13a of a module CB 13. When the modules 11 are mounted on the respective socketless LGAs 10 as shown in FIG. 2, the electrical contacts 5 of the socketless LGAs 10 are in contact with respective electrical contacts 12 (FIG. 3B) of the array disposed on the lower surface 13a of the module CB 13.

(14) In accordance with illustrative embodiments described herein, the frame members 3a-3c (FIGS. 1 and 2) of the host CB 2 that surround the mounting areas 3 abut the sides 13b-13d, respectively, of the module CB 13 when the modules 11 are mounted in the mounting areas 3. This abutment between the frame members 3a-3c and the sides 13b-13d, respectively, of the module CB 13 aligns the module 11 with the LGA 10 and brings the electrical contacts 5 of the array of the LGA 10 into contact with the respective electrical contacts 12 of the array of the module CB 13. When the modules 11 are mounted on the respective LGAs 10, the abutment of the electrical contacts 5 and 12 creates a small space in between the lower surface 13a of the module CB 13 and the upper surface 2a of the host CB 2.

(15) Because the LGAs 10 (FIGS. 1 and 2) are socketless, some mechanism other than plates and the like that are used with conventional LGA sockets must be used to provide the force needed to maintain contact between the electrical contacts 5 and 12 and to maintain a flat profile for the mounted configuration of the modules 11 on the respective LGAs 10. The manner in which this is accomplished in accordance with an illustrative embodiment will now be described with respect to FIGS. 1-4B.

(16) FIG. 4A illustrates a cross-sectional perspective view of the portion of the mounted configuration of the module 11 and its respective LGA 10 contained in the dashed circle 18 in FIG. 2 and taken along dashed line A-A′ in FIG. 2. FIG. 4B illustrates an enlarged view of the portion of the mounted configuration of the module 11 and its respective LGA 10 contained in dashed circle 19 in FIG. 4A. Once the module 11 has been mounted in the corresponding mounting area 3 on the corresponding LGA 10, a tool (not shown) holds the module 11 in position as an adhesive material 22 (e.g., epoxy or glue) is injected into the space in between the lower surface 13a of the module CB 13 and the upper surface 2a of the host CB 2 in the mounting areas 3. Prior to the adhesive material being injected, the parallel optical communications modules 11 can be tested to ensure that they perform satisfactorily prior to them being permanently secured to the LGA 10. This allows faulty modules 11 to be replaced before they are permanently secured to the LGA 10.

(17) In accordance with this illustrative embodiment, the module CB 13 has a through hole 21 (FIGS. 2-4B) formed in it through which the adhesive material 22 is injected. This feature allows the modules 11 to be mounted on the respective LGAs 10 prior to the adhesive material 22 being dispensed into the space between the lower surface 13a of the module CB 13 and the upper surface 2a of the host CB 2. The tool applies a sufficient amount of downward force in the direction indicated by arrow 15 in FIG. 2 to press the module 11 against the LGA 10 until the adhesive material sets, or cures. This ensures that the mounted configuration of the module 11 on the LGA 10 has a relatively flat profile (i.e., a short height on the host CB 2) and that the respective electrical contacts 5 and 12 of the arrays of the LGA 10 and of the module CB 13 are permanently secured to one another and are in good electrical contact with one another. The same tool or a different tool (not shown) may also be used to provide a force against the opposite side of the host CB 2 in a direction opposite the direction represented by arrow 15 (FIG. 2) to perform a support function similar to that provided by traditional backing plates. After the module 11 has been secured to the LGA 10, the tool can be removed, leaving only the mounted configuration of the module 11 on the LGA 10.

(18) It should be noted that although the illustrative embodiment uses the frame members 3a-3c of the host CB 2 to passively locate the modules 11 on the respective LGAs 10 to thereby passively align the respective electrical contacts 5 and 12 of the respective arrays, other devices and techniques may be used for this purpose. For example, mating features on the module and on the host CB (e.g., pins disposed on the upper surface 2a of the host CB 2 and complementarily-shaped and sized holes formed in the module CB 13) that mate with one another may be used for this purpose. Active alignment devices and techniques may also be used for this purpose. For example, it is known to use fiducial markings on a host CB and a machine vision system to locate and align elements on a CB. Particular features of the host CB 2 and of the module 11 can also be used to perform active alignment, such as the shape of the module 11 and the shape of one or more elements disposed on the host CB 2 and their spatial relationship to one another when viewed by the vision system. For example, the pattern of electrical contacts 5 of each LGA 10 may be used by a machine vision system as a fiducial on the host CB 2 to align the sides 13b-13d of the module CBs 13 with the respective LGAs 10. Known machine vision systems and pattern recognition techniques may be used for this purpose. In such cases, the need for the frame members 3a-3c or other passive alignment devices or features is eliminated.

(19) FIG. 5 illustrates a top view of a portion of a host CB 40 of a parallel optical communications module having a plurality of mounting areas 41, each of which is defined by four round pins 42 that are used for passive alignment and an array of electrical contacts 43. The portion of the host CB 40 within each of the mounting areas 41 and the corresponding array of electrical contacts 43 comprise a respective socketless LGA 50. FIG. 6 illustrates a top view of the socketless LGAs 50 shown in FIG. 5 with respective module CBs 51 mounted on them. In FIG. 6, one of the module CBs 51 is laterally offset from its respective socketless LGA 50 to show mating features 52 of the module CBs 51 that mate with the respective pins 42 of the respective socketless LGAs 50. The mating features 52 are semicircular corners of the CBs 51 that are complementary in shape and diameter to the circular or cylindrical side walls of the pins 42.

(20) In accordance with this illustrative embodiment, the pins 42 and the corners 52 operate as passive alignment features for passively locating or positioning the module CBs 51 on the respective mounting areas 41, which aligns the electrical contacts of an array (not shown) disposed on a lower surface of the module CB 51 with the respective electrical contacts 43 of the respective array of the LGA 50. An adhesive material such as epoxy or glue is dispensed onto one or both of the arrays of electrical contacts either before or after the modules have been mounted on the host CB 40 in one of the manners described above to secure the modules to the host CB 40.

(21) As is typically the case with host CBs, the host CBs 2 and 40 have electrical conductors (not shown) such as vias and traces running through them. These electrical conductors electrically interconnect the socketless LGAs of the host CBs with the other electrical circuitry mounted on the module CBs. For exemplary purposes, an integrated circuit chip 30 is shown mounted on the upper surface 2a of the host CB 2. In an illustrative embodiment, the chip 30 is a controller chip and the modules 11 are in communication with the controller chip 30 via the arrays of electrical contacts 5 and 12 and the electrical conductors routed in or on the host CB 2.

(22) It should also be noted that although the step of injecting the adhesive material into the space in between the upper and lower surfaces 2a and 13a of the host CB 2 and the module CB 13, respectively, has been described as occurring after the module 11 has been mounted on the LGA 10, the injection step may occur before the module 11 has been mounted on the LGA 10. In cases where the injection step is performed before the module 11 has been mounted on the LGA 10, the electrical contacts 5 and 12 should have structures that cause the adhesive material to be removed by the force of the physical contact between the respective electrical contacts 5 and 12 during the mounting process. In the latter case, greater force will be applied by the electrical contacts 5 and 12 to one another during the mounting process to cause the adhesive material to be removed to ensure good electrical contact between the respective electrical contacts 5 and 12. For that reason, in those embodiments, the electrical contacts 5 and 12 need to be strong enough to withstand such a force. In cases where the injection step is to be performed after the module 11 has been mounted on the LGA 10, the through hole 21 is merely on example of a solution for allowing the adhesive material to be injected into the space between the upper surface 2a of the host CB 2 and the lower surface 13a of the module CB 13. For example, the through hole could instead be formed through the host CB 2. As another example, the frame members 3a-3c could be modified to include a passage for introducing the adhesive material into the space between the upper surface 2a of the host CB 2 and the lower surface 13a of the module CB 13.

(23) It should be apparent from the above description of the illustrative embodiments that by obviating the need for an LGA socket the invention obviates the need to drill holes in the host CB 2 as well as the need for additional hardware (e.g., backing plates, screws, etc.). These features allow the area of the host CB 2 underneath the array of electrical contacts 5 to be used for routing of electrically-conductive pathways, such as vias and traces, reduce the overall cost of the LGA 10 and reduce the amount of time and effort that are needed to secure the modules 11 to the respective LGAs 10.

(24) It should be noted that the invention has been described with reference to illustrative embodiments for the purposes of demonstrating the principles and concepts of the invention. The invention, however, is not limited to these examples, as will be understood by persons of skill in the art in view of the description being provided herein. Many modifications may be made to the embodiments described while still achieving the goal of the invention.

(25) For example, although the illustrative embodiments have been described with reference to securing a parallel optical communications module to a host CB, the invention is not limited to use with parallel optical communications modules, but may be advantageously used with modules of any type that have arrays of electrical contacts that are to be interfaced with any array of a host CB. Also, in the illustrative embodiment demonstrated in FIGS. 1-4B, the electrical contacts 5 and 12 are metal pads and metal spring fingers, respectively, of the type that are often used to electrically interface an LGA with a CB. However, other types of electrical contacts may be used for this purpose. Persons of skill in the art will understand that these and other modifications may be made and that all such modifications are within the scope of the invention.