US20070178736A1

US20070178736A1 - Ball Grid Array Connector

Info

Publication number: US20070178736A1
Application number: US11/697,958
Authority: US
Inventors: Steven Minich; Donald Harper
Original assignee: FCI Americas Technology LLC
Current assignee: FCI Americas Technology LLC
Priority date: 2004-09-14
Filing date: 2007-04-09
Publication date: 2007-08-02
Also published as: CN101019280B; CN101019280A; WO2006031296A3; US7214104B2; WO2006031296A2; TW200623546A; WO2006031296A8; EP1794849A2; TWI283948B; EP1794849A4; EP1794849B1; US20060057897A1; MX2007001835A

Abstract

An electrical connector having an electrical contact with a terminal portion and a contact receiving wafer is disclosed. The connector may also include a contact receiving wafer having a face that at least partially defines an aperture that extends therethrough. A terminal portion of the contact may extend at least partially into the aperture. The faces that define the aperture allow the terminal portion of the contact to move in each of a plurality of directions, while also containing the terminal portion of the contact in each direction. The terminal portion of the contact may have connected a solder ball. The solder ball may define a diameter that is larger than the width of the aperture restricting movement of the wafer along a length of the contact.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 10/940,433, filed Sep. 14, 2004, the entirety of which is incorporated herein by reference.
The subject matter disclosed and claimed herein is related to the subject matter disclosed and claimed in co-pending U.S. patent application Ser. No. 10/294,966, filed Nov. 14, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 09/990,794, filed Nov. 14, 2001, now U.S. Pat. No. 6,692,272, and Ser. No. 10/155,786, filed May 24, 2002, now U.S. Pat. No. 6,652,318.
The subject matter disclosed and claimed herein is related to the subject matter disclosed and claimed in U.S. patent applications Ser. No. 10/940,329, filed Sep. 14, 2006, and Ser. No. 10/634,547, filed Aug. 5, 2003. The contents of each of the above-referenced U.S. patents and patent applications is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

Generally, the invention relates to electrical connectors. More particularly, the invention relates to ball grid array (“BGA”) connectors that allow for relative movement between the connector housing and leadframe assemblies contained within the housing, even after the connector is connected to a substrate such as a printed circuit board.

BACKGROUND OF THE INVENTION

Printed circuit boards (“PCBs”) are commonly used to mount electronic components and to provide electrical interconnections between those components and components external to the PCB. One problem with conventional PCBs is flexing. PCBs flex under the weight of attached electrical components when subject to vibrations, assembly, and handling loads. Ultimately, the PCB with attached electrical components are assembled in a chassis, such as in a computer system. Handling and transit of the chassis assembly can cause PCB flexing under the weight of the components.
Additionally, electrical components are becoming increasingly heavy. Electrical components that are attached to the PCB include, among others, the heat sink and fan assembly which is attached to the central processing unit (CPU). These assemblies often are upwards of a pound or more in weight, putting an increased burden on the PCB.
In an effort to increase electrical component density on the PCB, electrical components may be attached to the PCB using BGA technology. A BGA microprocessor, for example, makes its electrical connection via a solder ball on each connector of the BGA of the electrical microprocessor and the electrical contacts on the surface of the PCB. BGA components require a rigid substrate to which they are attached. In effect, these BGA components are soldered directly to the circuit board without intervening contacts or wires. BGA components commonly incorporate tens or hundreds of solder connections between the ball-grid package and the circuit board. Any appreciable circuit board flexing may cause the solder connections to shear, compress, fatigue, and subsequently break.
There is a significant need in the art to provide a BGA connector that has the ability to flex under various loads to minimize stresses imposed on the solder ball connections.

SUMMARY OF THE INVENTION

An electrical connector may include an electrical contact with a terminal portion and a contact receiving wafer. The contact receiving wafer may have a face that at least partially defines an aperture that extends through the wafer. The terminal portion of the electrical contact may extend at least partially into the aperture. The aperture may allow the terminal portion of the contact to move in a first direction. The face of the wafer may contain the terminal portion in the first direction.
The electrical connector may include a solder ball connected to the terminal portion of the contact. The solder ball may have a diameter that is larger than the width of the aperture. Thus, the solder ball may restrict movement of the wafer along a length of the contact.
The electrical connector may also include a leadframe. The electrical contact may at least partially extend through the leadframe. The wafer may be contained between the solder ball and the leadframe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict an example embodiment of a connector according to the invention.
FIG. 2 depicts an example embodiment of an insert molded leadframe assembly according to the invention.
FIG. 3 provides a partial view of an example embodiment of a ball grid array connector according to the invention, without a wafer or solder balls.
FIG. 4 provides a partial view of an example embodiment of a ball grid array connector according to the invention, without solder balls.
FIG. 5 provides a partial view of a ball grid array formed on a plurality of electrical contacts, without a wafer.
FIG. 6 provides a perspective bottom view of a connector according to the invention with solder posts attached to a housing.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 1A and 1B depict an example embodiment of a ball grid array (“BGA”) connector 100 according to the invention having a ball grid side 100A (best seen in FIG. 1A) and a receptacle side 100B (best seen in FIG. 1B). Though the connector described herein is depicted as a ball grid array connector, it should be understood that through pin mounting or surface mounting other than BGA may also be used. As shown, the BGA connector 100 may include a housing 101, which may be made of an electrically insulating material, such as a plastic, for example, that defines an internal cavity. The housing 101 may contain one or more insert molded leadframe assemblies (“IMLAs”) 115. In an example embodiment, the housing 101 may contain ten IMLAs 115, though it should be understood that the housing 101 may contain any number of IMLAs 115.
FIG. 2 depicts an example embodiment of an IMLA 115. As shown, the IMLA 115 may include a set of one or more electrically conductive contacts 211 that extend through an overmolded housing 215. The overmolded housing 215 may be made of an electrically insulating material, such as a plastic, for example. Adjacent contacts 211 that form a differential signal pair may jog toward or away from each other as they extend through the overmolded housing 215 in order to maintain a substantially constant differential impedance profile between the contacts that form the pair. For arrangement into columns, the contacts 211 may be disposed along a length of the overmolded housing 215 (e.g., along the “Y” direction as shown in FIG. 2).
The contacts 211 may be dual beam receptacle contacts, for example. Such a dual beam receptacle contact may be adapted to receive a complementary beam contact during mating with an electrical device. As shown in FIG. 2, each contact 211 may have a dual beam receptacle portion 217 and a terminal portion 216. The terminal portion 216 may be adapted to receive a solder ball 120 as described below.
An IMLA 115 may also include one or more containment tabs 204. In an example embodiment, a respective tab 204 may be disposed on each end of the IMLA 115. For example, the contact 211 at the end of the IMLA 115 may have a tab 204 that extends beyond a face of the overmolded housing 215. In such an embodiment, the tab 204 may be made of the same material as the contact 211 (e.g., electrically conductive material). Alternatively, the tabs 204 may extend from the overmolded housing 215, and may be attached to the overmolded housing 215 or integrally formed with the overmolded housing 215. In such an embodiment, the tab 204 may be made of the same material as the overmolded housing 215 (e.g., electrically insulating material).
As best seen in FIG. 3, the connector housing 101 may include one or more tab receptacles 302. In an example embodiment, a respective pair of tab receptacles 302 are arranged on opposite sides of the housing 101 to contain an associated IMLA 115 in a first direction (such as the Y-direction shown in FIG. 3). Each tab receptacle 302 may have an opening 322 for receiving a respective tab 204. Each such opening may be defined by a plurality of faces 332 formed within the tab receptacle. The tab receptacles 302 may be resilient so that they may be displaced enough to insert the associated IMLA 115 into the housing 101. With the IMLA 115 inserted into the housing 101, the tab receptacle 204 may snap back, and thus, the tabs 204 may be set within the openings 322 in the tab receptacles 302. According to an aspect of the invention, the tab receptacles 302 may contain the IMLAs within the housing in all directions, and also allow for movement of the IMLAs 115 in all directions within the housing.
To allow movement of the IMLAs 115 in the Y-direction, the leadframes 215 need not extend all the way to the inner surface 305 of the tab receptacle 302. When an end of the overmolded housing 215 meets the inner surface 305 of the associated tab receptacle 302, the tab receptacle 302 prevents the overmolded housing 215 from moving any further in the Y-direction. The distance the IMLA 115 may move relative to the housing 101 in the Y-direction may be controlled by regulating the distance between the end of the overmolded housing 215 and the inner surface 305 of the housing 101. Thus, the tab receptacles 302 may contain the IMLAs 115 in the Y-direction within the housing 101, while allowing movement of the IMLAs in the Y-direction.
To allow movement of the IMLA 115 relative to the housing 101 in the X-and Z-directions, the receptacle openings 322 may be made slightly larger than the cross-section (in the X-Z plane) of the tabs 204 that the openings 322 are adapted to receive. When the tab 204 meets one of the faces 332, the face 332 prevents the tab 204 (and, therefore, the overmolded housing 215) from moving any farther in whichever direction the IMLA 115 is moving (e.g., the X- or Z-direction). The relative difference in size between the receptacle opening 322 and the cross-section of the tab 204 determines the amount the IMLA 115 may move relative to the housing 101 in the X- and Z-directions. Thus, the tab receptacles 302 may contain the IMLAs 115 in the X- and Z-directions, while allowing movement of the IMLAs in the X-Z plane. In an example embodiment of the invention, the tabs 204 may have dimensions of about 0.20 mm in the X-direction and about 1.30 mm in the Z-direction. The receptacle openings 322 may have dimensions of about 0.23 mm in the X-direction and about 1.45 mm in the Z-direction. The distance between each end of the overmolded housing 215 and the respective inner surface 305 of the housing 101 may be about 0.3 mm.
As shown in FIG. 1, a connector 100 according to the invention may include a ball grid array 148. The ball grid array 148 may be formed by forming a respective solder ball 120 on the terminal end 216 of each of the electrical contacts 211. Thus, the ball grid array connector 100 may be set on a substrate, such as a printed circuit board, for example, having a pad array that is complementary to the ball grid array 148.
According to an aspect of the invention, the connector 100 may include a contact receiving substrate or wafer 107 that contains the terminal ends of the contacts, while allowing for movement of the terminal ends. The wafer 107 may be made of an electrically insulating material, such as a plastic, for example.
As best seen in FIG. 4, the wafer 107 may include an array of apertures 456. Each aperture 456 may receive a respective terminal portion 216 of a respective contact 211. Each aperture 456 is defined by a respective set of faces 478 that contain the terminals in the X-and Y-directions. To allow movement of the terminals in the X- and Y-directions, the apertures 456 may be slightly larger than the cross-section (in the X-Y plane) of the terminals 216 that the apertures 456 are adapted to receive. As shown, the faces 478 may define the aperture 456 such that at least one of the faces has a length that is greater than the width of the contact. Thus, the terminal portion of the contact may sit freely, or “float,” within the aperture 456. That is, the terminal portion of the contact need not necessarily touch any of the faces that define the aperture 456. The relative difference in size between the aperture 456 and the terminal 216 determines the amount the terminal may move in the X- and Y-directions. Thus, the wafer 107 may contain the terminal portions 216 of the contacts 211 in the X- and Z-directions, while allowing movement of the terminal portions 216 in the X-Y plane.
As shown, the apertures 456 may be generally square, though it should be understood that the apertures 456 may be defined to have any desired shape. In an example embodiment of the invention, the terminal portions 216 of the contacts 211 may have dimensions of about 0.2 mm by about 0.3 mm. The apertures 456 may have dimensions of about 0.6 mm by about 0.6 mm.
To manufacture the connector 100, the IMLAs 115 may be inserted and latched into the housing 101 as described above. The wafer 107 may then be set on the ball-side faces 229 of the overmolded housing 215, with the terminal portions 216 of the contacts 211 extending into the apertures 456. Respective solder balls 120 may then be formed on the terminal portions 216 of the contacts 211 using known techniques. FIG. 5 depicts a plurality of solder balls 120 formed on respective terminal portions 408 of contacts that extend through overmolded housing 215. Note that FIG. 5 depicts the connector with solder balls but without the wafer, though it is contemplated that the wafer will be set onto the leadframes before the solder balls 120 are formed.
To form a solder ball on a terminal end of the contact, solder paste may be deposited into the aperture 456 into which the terminal end of the contact extends. A solder ball may be pressed into the solder paste against the surface of the wafer 107. To prevent the contact from being pulled into the housing through the aperture, the diameter of the solder ball may be greater than the width of the aperture. The connector assembly (which includes at least the contact in combination with the housing and the wafer) may be heated to a temperature that is greater than the liquidous temperature of the solder. This causes the solder to reflow, form a generally spherically shaped solder mass on the contact tail, and metallurgically bond the solder ball to the contact.
Preferably, the aperture 456 has a width that is less than the diameter of the solder ball so that the solder ball prevents the contact from being able to be pulled into the housing. Similarly, the diameter of the solder ball being greater than the width of the aperture enables the wafer 107 to be contained between the solder balls 120 and the overmolded housings of the leadframe assemblies.
As shown in FIG. 6, the connector housing 115 may also include one or more solder posts 160. The solder posts 160, which may contain solder or solderable surfaces, may be adapted to be received in orifices defined by a PCB board.
The IMLAs may be free to move with respect to the housing 115, as described above, prior to reflow of the solder balls. This movement, or float, allows the IMLAs to self-align during reflow of the solder balls. For example, when the solder balls liquefy during reflow, surface tension in the liquid solder produces a self-aligning effect. The present invention allows the IMLAs to benefit from the self-aligning properties of the liquid solder balls. Once reflow is complete, the contacts, housing, and solder posts are fixed with respect to the PCB. The affixed solder posts help prevent forces acting on the housing, in a direction parallel to the PCB, to transmit to the solder balls.
It is to be understood that the foregoing illustrative embodiments have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the invention. Words which have been used herein are words of description and illustration, rather than words of limitation. Further, although the invention has been described herein with reference to particular structure, materials and/or embodiments, the invention is not intended to be limited to the particulars disclosed herein. Rather, the invention extends to all functionally equivalent structures, methods, and uses, such as are within the scope of the appended claims. Those skilled in the art, having the benefit of the teachings of this specification, may affect numerous modifications thereto and changes may be made without departing from the scope and spirit of the invention in its aspects.

Claims

1. An electrical connector comprising:

an electrical contact having a terminal portion;

a leadframe housing through which the contact at least partially extends; and

a contact receiving wafer having a face that at least partially defines an aperture that extends through the wafer, wherein the wafer abuts the leadframe housing and is adapted to remain part of the connector when the electrical contact is electrically connected to an electrical device, and wherein the terminal portion of the contact extends at least partially into the aperture, the aperture allows the terminal portion of the contact to move in a first direction without abutting the face, and the face contains the terminal portion of the contact in the first direction.

2. The electrical connector of claim 1, wherein the aperture allows the terminal portion of the contact to move in a second direction, and the wafer has a second face that at least partially defines the aperture and contains the terminal portion of the contact in the second direction.

3. The electrical connector of claim 2, wherein the second direction is orthogonal to the first direction.

4. The electrical connector of claim 1, further comprising a solder ball connected to the terminal portion of the contact.

5. The electrical connector of claim 4, wherein the solder ball restricts movement of the wafer along a length of the contact.

6. The electrical connector of claim 4, wherein the solder ball restricts movement of the contact into the aperture.

7. The electrical connector of claim 4, wherein the wafer is contained between the solder ball and the lead frame.

8. The electrical connector of claim 4, wherein the aperture has a width and the solder ball has a diameter that is larger than the width of the aperture.

9. A contact receiving wafer for an electrical connector, the electrical connector comprising a leadframe housing through which an electrical contact at least partially extends, the contact receiving wafer comprising:

a substrate having a plurality of apertures extending therethrough, wherein each said aperture is at least partially defined by a respective face and is adapted to receive in a first direction a respective terminal portion of the respective electrical contact, and wherein each said aperture allows the respective terminal portion of the respective electrical contact to move in a second direction perpendicular to the first direction without abutting the face that defines the aperture after the electrical connector is attached to a second electrical connector, and wherein each face contains the terminal portion of the respective electrical contact received therein in the second direction, wherein the substrate is configured to abut the leadframe housing.

10. An electrical connector comprising:

an electrical contact having a terminal portion;

a leadframe housing through which the contact at least partially extends;

a contact receiving wafer having a face that at least partially defines an aperture that extends through the wafer, wherein the contact receiving wafer abuts the leadframe; and

a solder ball connected to the terminal portion of the contact,

wherein the terminal portion of the contact extends at least partially into the aperture, the aperture allows the terminal portion of the contact to move in a first direction without abutting the face, and the face contains the terminal portion of the contact in the first direction.

11. The electrical connector of claim 10, wherein the aperture allows the terminal portion of the contact to move in a second direction, and the contact receiving wafer has a second face that at least partially defines the aperture and the second face contains the terminal portion of the contact in the second direction.

12. The electrical connector of claim 11, wherein the second direction is orthogonal to the first direction.

13. The electrical connector of claim 10, wherein the solder ball restricts movement of the wafer along a length of the contact.

14. The electrical connector of claim 10, wherein the solder ball restricts movement of the contact into the aperture.

15. The electrical connector of claim 10, wherein the wafer is contained between the solder ball and the lead frame.

16. The electrical connector of claim 10, wherein the aperture has a width and the solder ball has a diameter that is larger than the width of the aperture.

17. The contact receiving wafer of claim 9 wherein each said aperture is square.

18. The contact receiving wafer of claim 11 wherein each said aperture has the dimensions of about 0.6 mm by 0.6 mm.

19. The electrical connector of claim 12, further comprising a connector housing, the connector housing having a post adapted to be received in an orifice defined by a circuit board.

20. The electrical connector of claim 19, wherein the post comprises a solderable surface.