WO2010105086A1

WO2010105086A1 - Contact with tubular solder member

Info

Publication number: WO2010105086A1
Application number: PCT/US2010/027027
Authority: WO
Inventors: Joseph S. Cachina; James R. Zanolli
Original assignee: Interplex Industries, Inc.
Priority date: 2009-03-11
Filing date: 2010-03-11
Publication date: 2010-09-16
Also published as: CN102355979B; CN102355979A

Abstract

An electrical connector configured to be electrically connected to a substrate. The electrical connector includes a housing with a plurality of electrical contact terminals disposed on a connection surface thereof. Each electrical contact terminal includes an elongate tail portion extending from the connection surface. The elongate tail portion of each electrical contact terminal is disposed in a central opening of a tubular reflowable element. The tail portion may optionally include a stress or tension relief mechanism. The tubular reflowable element extends beyond a free end of the elongate tail portion away from the connection surface. The electrical contact terminals are configured to be disposed in the vicinity of a corresponding substrate terminal such that the reflowable element of each electrical contact terminal electrically connects the contact terminal to the corresponding substrate terminal.

Description

CONTACT WITH TUBULAR SOLDER MEMBER

FIELD

[0001] The present invention relates to electrical contacts for providing an electrical connection between first and second electronic components, and more specifically relates to electrical contacts having a reflowable element disposed thereon.

BACKGROUND

[0002] Electrical connectors are frequently attached to a substrate, such as a printed circuit board (PCB), using a Ball Grid Array (BGA) type of electrical connection . The BGA includes a plurality of solder balls that are used to connect electrical contacts of the connector to the PCB. A typical BGA connector is connected to an array of electrical contact pads or traces disposed about the surface of the substrate. The solder balls are attached to the contact pads by first applying a resin flux to the electrical contact pads, positioning the solder balls onto the electrical contact pads, and running the connector through a reflow furnace. During the reflow process the solder balls are held in position by the flux and wetted onto the electrical contact pads. In addition to holding the solder balls in position, the flux promotes the wetting of the solder balls to the contact pads and chemically cleans the contact pad surfaces.

[0003] However, the spherical shape of the solder balls in a BGA connection results in a short connection height between the electrical contacts of the connector and the contact pads of the substrate. These short connections are subject to high mechanical stress if any movement occurs between the connector and the substrate. As a result, the connection between the connector and the substrate is vulnerable to failing as a result of the solder connection breaking due to stress. [0004] One approach to apply longer solder members on the contacts involves, for example, solder members of a column grid array. However, this is a very complex and time consuming process. One such process includes reflowing solder in an array of containers or molds, disposing a contact into each container, allowing the solder to cool and then removing the contacts with the solder thereon. The requirement to heat and cool the solder as it is applied to the contacts can be both costly and time consuming.

SUMMARY

[0005] The present invention provides an electrical connector configured to be electrically connected to a substrate. The electrical connector includes a housing with a number of electrical contact terminals disposed on a connection surface thereof. Each electrical contact terminal includes an elongate tail portion extending from the connection surface. The elongate tail portion of each electrical contact terminal is disposed in a central opening of a tubular reflowable element. The tubular reflowable element extends beyond a free end of the elongate tail portion away from the connection surface. The electrical contact terminals are configured to be disposed in the vicinity of a corresponding substrate terminal such that the reflowable element of each electrical contact terminal electrically connects the contact terminal to the corresponding substrate terminal.

[0006] In an embodiment, the reflowable element can be disposed on the tail portion of each electrical contact terminal by pushing the tail portion into the central opening of the reflowable element. This can reduce production costs and time by obviating the need to heat and cool the reflowable material to place it on the tail portion of the contact.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Exemplary embodiments of the present invention will be described in the following and are schematically shown in the drawings, in which: [0008] Fig. 1 shows an electrical contact terminal and a tubular reflowable element in accordance with an embodiment of the invention;

[0009] Fig. 2 shows the contact terminal disposed in the tubular reflowable element of Fig. 1;

[0010] Fig. 3 shows the contact terminal and reflowable element of Fig. 1 disposed adjacent a substrate terminal;

[0011] Fig. 4 shows the contact terminal attached to the substrate terminal of Fig. 3 after reflow;

[0012] Figs. 5-7 show steps of placing reflowable elements onto terminal contacts in accordance with an embodiment of the invention;

[0013] Figs. 8 and 9 show steps of connecting the terminal contacts of Figs. 5-7 to a substrate;

[0014] Fig. 10 and 11 show an alternative embodiment of an electrical contact terminal and reflowable member in accordance with the invention;

[0015] Figs. 12 and 13 show an alternative embodiment of an electrical contact terminal and reflowable member in accordance with the invention; and

[0016] Fig. 14 shows the electrical contact terminal of Figs. 12 and 13 connected to a substrate.

DETAILED DESCRIPTION

[0017] Fig. 1 shows an electrical contact terminal 2 and a conductive reflow element 4 in accordance with an embodiment of the present invention. The electrical contact terminal 2 includes an elongate tail portion 6 that extends away from a body 8 of the contact terminal 2. The conductive reflow element 4 includes a first reflowable material 10 having an elongate tubular shape. As illustrated by Figs. 1 and 2, the reflow element 4 is disposed on the electrical contact terminal 2 by pushing the tail portion 6 of the contact terminal 2 into a central opening of the tubular reflowable material 10. Once the reflow element 4 is placed on the tail portion 6, a lower end of the reflow element 4 is disposed adjacent a corresponding conductive terminal 12 of a substrate 14, such as a printed circuit board (PCB) as shown in Fig. 3. The reflow element 4 is then brought to an elevated reflow temperature causing it to adhere to the conductive substrate terminal 12 and the tail portion 6 of the contact terminal 2. As a result, the electrical contact terminal 2 is electrically and mechanically connected to the substrate at the substrate terminal 12 with a solder connection 11, as shown in Fig. 4.

[0018] An example of a reflowable material 10 that is suitable with the present invention is solder. Solder can be used as the reflowable material 10 because it will reflow at elevated temperatures that are below the melting point of the components it is connecting and the surrounding components. For example, depending on the particular material, solder can have a melting point in a range between 9O⁰C and 45O⁰C. Accordingly, the solder can reflow and connect the contact terminal 2 to the substrate terminal 12 without altering or melting the contact terminal 2, the substrate terminal 12, the substrate 14 or any structural element near the solder, such as a housing holding the contact terminal. An exemplary suitable solder material is composed of a mixture of tin and lead. Due to regulatory pressure to reduce the amount of lead used in electrical components, it may be advantageous to use a lead- free solder. Examples of lead-free solders frequently include tin combined with other materials such as copper, silver, bismuth, indium, zinc and antimony. Many suitable solders have a reflow temperature that is below 220⁰C. The exemplary embodiment of a solder element 4 including a tubular solder material 10 is an example of a reflowable element throughout this description.

[0019] The solder element 4 shown in Figs 1-4 includes a core of flux 16 disposed within the central opening of the tubular solder material 10. The flux 16 can serve several purposes when the solder reflows. First, it removes oxidation from the surfaces that are electrically connected. The flux 16 also aids in the soldering process improving the wetting characteristics of the liquid solder material 10 when it is subjected to an elevated temperature. When the contact terminal 2 is inserted into the solder element 4, as shown in Fig. 2, the tail portion 6 of the contact terminal is pushed into the flux 16. Many suitable flux materials are malleable at room temperature. Accordingly, the tail portion 6 can be inserted into the central opening of the solder element 4 without elevating the temperature to a point near the reflow temperature. As the tail portion 6 is inserted, the flux 16 is pushed out of the way. Accordingly, the tail portion 6 can be pushed into the tubular solder element 4 at a temperature substantially below the reflow temperature of the solder. For example, depending on the solder used, the tail portion 6 can be inserted into the tubular element 4 at a temperature substantially below 220⁰C or even substantially below 90⁰C. However, in other embodiments, the flux core 16 may be pushed down and out of the tubular solder material 10 without any deformation of the solder occurring.

[0020] The substrate terminal 12 is illustrated in Figs. 3 and 4 as a contact pad. The contact pad includes a layer of solder paste 18 disposed thereon before reflow of the solder. The solder paste 18 aids in soldering the contact terminal 2 to the substrate terminal 12 by promoting the wetting of the contact pad with the solder material 10 and by protecting the contact pad 12 from the air before the solder process. As an example, the solder paste can include powdered solder material suspended in a medium of flux.

[0021] As shown in Fig. 2, the tail portion 6 of the contact terminal 2 can have a length that is shorter than the tubular solder element 4, such that a section 20 of the solder element 4 extends below a free end 22 of the tail portion 6. This extended section 20 allows for the solder connection 11 to have an extended length compared to that formed by a solder ball. As a result, the solder connection 11 is less susceptible to breaking from mechanical stress caused by slight movements between the housing holding the contact terminal 2 and the substrate 14.

[0022] In accordance with the present invention, an exemplary method of applying tubular solder elements 4 on the tail portions 6 of a group of contact terminals 2 is shown in Figs. 5 through 7. Fig. 5 shows a group of contact terminals 2 extending from an electrical connection surface 25 of a connector housing 24. The electrical connection surface 25 may be virtually any conductive material for connecting one electrical component to another. In some embodiments, connector housing 24 is part of a connector for connecting substrate 14 to another substrate, another connector, or the like. In these embodiment, electrical connection surface 25 provides parallel connection between each contact terminal 2 (which is ultimately connected to substrate 14 after soldering) and each corresponding electrical contact (not shown, and which is ultimately connected to another substrate or another connector). The tail portions 6 of the contact terminals extend away from the housing 24 in a substantially uniform and parallel direction. In the illustrated embodiment, a small portion of the body 8 of the contact terminals extends just slightly out of the connector housing 24. However, it is also possible that the body of the contact terminals be held entirely within the housing 24 and only the tail portions 6 extend outward therefrom. To apply the tubular solder elements 4 onto the tail portions 6, the housing 24 is brought in the vicinity of a holder 26 for the solder elements. Each of the tail portions 6 is lined up with a corresponding tubular solder element 4 that is held in a cavity 28 within the holder 26. As shown in Fig. 6, the tail portions 6 of the contact terminals 4 are placed immediately adjacent to the tubular solder elements 4. The housing 24 is then moved toward the holder 26 such that each tubular solder element 4 is pushed onto a corresponding tail portion 6, as shown in Fig. 7.

[0023] Once the tubular solder elements 4 have been placed on the contact terminals 2, the connector housing 24 is disposed in the vicinity of the substrate 14 or PCB. The connector housing 24 is then carefully placed so that the solder element 4 of each contact terminal 2 is positioned adjacent the substrate contact 12 of the substrate 14 with the solder paste 18 therebetween, as shown in Fig. 8. To clearly illustrate the substrate contacts 12 and solder paste 18, the substrate contacts 12 extend up from the substrate and the solder paste 18 only covers a portion of the contact 12, in a step-like fashion. However, in many embodiments, the substrate contacts 12 will be substantially flush with the substrate 14 and the solder paste 18 will cover the contacts 12 in their entirety. The present invention contemplates all such variations.

[0024] To electrically connect the connector housing 24 to the substrate 14, the solder 10 of each solder element 4 is then heated such that the solder reflows. As a result, a solder connection 11 is formed between each contact terminal 2 and corresponding substrate contact 12, as shown in Fig. 9.

[0025] Figs. 10 and 11 show another embodiment of the connector of the invention, in which the tubular element 4 has an open core instead of having a flux core, as in Figs. 1-4. The open core solder element can be free of any flux, as illustrated, or it can have flux disposed elsewhere on the element, such as on the outer surface of the tubular element or within the tubular element. In this embodiment, the tail portion 6 of the terminal contact is pushed into the open core so that a surface of the tail portion engages with an inner surface 28 of the tubular solder element 4. To ensure that the solder element 4 will be securely held on the contact terminal, the tail portion 6 can have a substantially similar, or slightly larger, diameter than the diameter of the inner surface 28 of the tubular solder element 4. Accordingly, the tail portion 6 fits tightly within the open core.

[0026] Figs. 12-14 illustrate yet another embodiment of the contact terminals 4 that aid in relieving mechanical stress on the solder connection 11. The tail portion 6 of each contact terminal 4 can be similar to the previously described embodiments and inserted into the flux core 16 or open core of the solder element 4 as described above. However, the contact terminals 4 can also include a stress or tension absorbing or spring element 32 disposed between the body 8 and the free end 22 of the contact terminal 4. The spring element 32 can be part of the tail portion 6 or it can be a separate part of the contact terminal. The spring element 32 is left outside of the tubular solder element 34 when the tail portion 6 is inserted therein. As a result, the spring element 32 is positioned between the solder connection 11 and the connector housing 24 when the housing 24 and substrate 14 are electrically connected. Accordingly, the mechanical stress caused by any slight movement between the connector housing 24 and the substrate 14 can be absorbed by the spring element 32. The spring element 32 can be formed by one or more bends 34 in the terminal contact 4. The illustrated spring element 32 includes three bends. Thus, the shown element can absorb stresses caused by movement of the substrate 14 and connector housing 24 toward each other, away from each other or in a lateral direction.

[0027] Although the preferred form of the invention has been shown and described, many features may be varied, as will readily be apparent to those skilled in this art. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

What is claimed is:

1. An electrical connector for electrical connection to a substrate, the connector comprising: a housing with an electrical connection surface; a plurality of electrical contact terminals disposed on the electrical connection surface, wherein each electrical contact terminal of the plurality of electrical contract terminals has an elongate tail portion extending away from the electrical connection surface; and a plurality of tubular reflowable elements, wherein each tubular reflowable element of the plurality of tubular reflowable elements is disposed on a corresponding elongate tail portion.

2. The electrical connector Claim 1, wherein each tubular reflowable element of the plurality of tubular reflowable elements is composed of solder.

3. The electrical connector of Claim 1, wherein each tubular reflowable element of the plurality of tubular reflowable elements has a melting point that is lower than a melting point of each of the plurality of electrical contact terminals, and wherein the melting point of each tubular reflowable element of the plurality of tubular reflowable elements is lower than a melting point of the housing.

4. The electrical connector of Claim 1, wherein each elongate tail portion is parallel to each of the other elongate tail portions, and each of the elongate tail portions extends in a uniform direction relative to each other.

5. The electrical connector of Claim 1, wherein each of the plurality of electrical contacts includes a body, wherein a small portion of each body extends out of the housing.

6. The electrical connector of Claim 1, wherein each of the plurality of electrical contacts includes a body, wherein each body is held entirely within the housing.

7. The connector of Claim 1, wherein each tubular reflowable element of the plurality of tubular reflowable elements is disposed on a corresponding elongate tail portion such that a portion of each tubular reflowable element extends beyond a free end of the corresponding tail portion in a direction away from the electrical connection surface.

8. The electrical connector of Claim 1, wherein each of the plurality of electrical contact terminals further includes: a body, and a spring element disposed between the body and the elongated tail portion.

9. The electrical connector of Claim 8, wherein each of the spring elements includes at least one bend.

10. The electrical connector of Claim 1, wherein each of the plurality of electrical contact terminals further includes a body, and wherein for each of the plurality of electrical contact terminals, the elongated tail portion of the electrical contact terminal includes a spring element, wherein the spring element is disposed between the body and the free end of the elongated tail portion of the electrical contact terminal.

11. The electrical connector of Claim 10, wherein each of the spring elements includes at least one bend.

12. The electrical connector of Claim 1 , wherein each tubular reflowable element of the plurality of tubular reflowable elements has a central opening, and wherein each elongate tail portion of the electrical contract terminal is inserted into the corresponding central opening such that the tail portion of the electrical contact terminal fits tightly within the corresponding central opening.

13. The electrical connector of Claim 12, wherein the central opening further includes a core of flux, wherein the core of flux is malleable at a temperature that is lower than the melting point of each tubular reflowable element of the plurality of tubular reflowable elements.

14. An electrical connector for electrical connection to a substrate, the connector comprising." an electrical contact terminal having a tail portion; and a tubular reflowable element having a central opening, wherein the tubular reflowable element is disposed on the tail portion such that the tubular reflowable element is inserted within the central opening of the tubular reflowable element.

15. The electrical connector of Claim 14, wherein the tubular reflowable element is disposed on the tail portion such that the tubular reflowable element extends beyond a free end of the tail portion.

16. The electrical connector of Claim 14, wherein the tubular reflowable element has a melting point that is lower than a melting point of the electrical contact terminal.

17. A method for electrical connection to a substrate, comprising: inserting an elongated tail portion of an electrical contact terminal into an open cavity of a tubular reflowable element

18. The method of Claim 17, wherein inserting the elongated tail portion of the electrical contact terminal into the open cavity is accomplished such that a portion of the tubular reflowable element extends beyond a free end of the elongated tail portion.

19. The method of Claim 17, wherein the tubular reflowable element has a melting point that is lower than a melting point of the electrical contact terminal.

20. The method of Claim 17, further comprising: disposing a lower end of the tubular reflowable element adjacent to a conductive terminal of the substrate; and adhering the reflowable element to the substrate, wherein the adhering is accomplished by: elevating an ambient temperature to a temperature that is greater than a melting point of the tubular reflowable element, less than a melting point of the electrical contact, and less than a melting point of the substrate.