ELECTRICAL CONNECTOR AND METHOD OF MAKING IT
The present invention is an electrical connector in which a substrate (such as a printed circuit board or PCB) includes a plurality of apertures (or vias) and some of those apertures are filled with two materials to improve the characteristics of the electrical interconnection. The preferred process of crating the filled vias includes the steps of plating the vias with an electrically-conductive material to create an electrically-conductive path between portions of the substrate and components associated with the substrate and partially filling the apertures, then filling at least a portion of the apertures or vias with a second or different filling material to seal at least apart of the electrically conductive path through the plating. The second filling material may be chosen to provide thermal compensation for the connection.
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1. Field of Invention
The present invention relates to an improved electrical connector and method of making it. More specifically, the present invention relates to an electrical connector comprising elastic contacts on an insulating substrate, in which vias or holes in the insulating substrate are filled to provide a better connector performance and improved ease of manufacturing.
2. Background Art
Electrical connectors are an important component of many electronic devices. As the devices become smaller, the functionality is increasing, requiring increasing numbers of electrical interconnections between components. In order to enable system miniaturization, the electrical connectors must become smaller, yet they are required to handle increasing power and signal loads and to operate at faster speeds. It is necessary in many applications to provide a low-cost, high reliability electrical interconnection on an extremely small scale to allow for an increasing number of components to be interconnected. As the operating frequencies and data transfer rates of the electronic system increases, there is an increased need for high speed signal integrity through the connector.
Various electrical connectors have been proposed in the prior art. Examples of such electrical connector (electrical interconnection) is shown in Neoconix' prior patents such as U.S. Pat. No. 7,113,408.
Conventional electrical connectors present challenges in terms of their size, cost, and operating speed. A conventional connector has a substantial size and a significant cost to manufacture, especially when the connector includes many electrical contacts. Such connectors also must operate at speeds which are increasing without losing data as a result of the electrical connections. Power handling requirements are also increasing. Conventional connectors are limited in power handling capability, and can overheat when power load exceeds their capability. These conventional connectors are typically lacking in their ability to dissipate heat or to conduct heat away from the mating components.
Further, many electrical connectors utilize precious metal surface finishes, such as gold, to prevent corrosion. These materials are costly. As a result there is a desire to use smaller connections (to take up less space and to use less precious material), and to minimize the surface area which must be finished with the precious metals.
Electronic devices and particularly portable electronic devices are susceptible to corrosion and degradation from liquids or gases from the environment that penetrate the system. Electrical connectors typically have a high density of electrical interconnections, and it is difficult to shield these from the environment while maintaining connector separability. In contrast, interconnections on a packaged semiconductor can be over-molded or under-filled to protect the interconnections from moisture, water, or gas ingress. Hence, the electrical connector tends to be a highly susceptible component from the perspective of water ingress or damage from corrosive environments.
Accordingly, it will be apparent that the prior art electrical connectors have limitations and undesirable characteristics.
SUMMARY OF THE INVENTIONThe present invention overcomes the limitations and disadvantages of the prior art electrical connectors and methods of making them.
The present invention is an improved electrical connector and method of making it in which the electrical connector may have dense interconnections, and which provides high reliability interconnections, low resistance and high current carrying capacity, improved thermal dissipation, reduced precious metal usage during fabrication, and thin electrical conductors while providing improved protection for the electrical interconnections. This method and connector will allow for smaller scale interconnections and greater reliability of the interconnection while providing improved signal integrity at high frequency and an economical electrical connector to manufacture.
Other objects and advantages of the present invention will be apparent to those skilled in the relevant art in view of the following description of the preferred embodiment and the accompanying drawings.
The substrate 12 is typically non-conducting and made starting with a printed circuit board (PCB) material such as a sheet of copper-clad FR4. The substrate 12 as shown in this
The plated through holes are typically formed through a drilling process followed by a process to make the hole walls electrically conductive, after which the hole walls are plated through a chemical or electrochemical process which allows for the wall of the electrically conductive via 18a to be of a controlled thickness to provide sufficient conductivity and reliability. The standard through hole or via 18 with plating 18a of the prior art electrical connectors is thus not filled completely, but only around the periphery of the cylindrical opening, having a hollow or open center portion, represented by the reference numeral 18c.
The preferred fill material 18b for many applications of the present invention is thermosetting epoxy, a plastic material. However, other materials can be used to advantage in the present invention including other thermo-setting materials (such as acrylic, polyimide, or Bakelite) or thermoplastic material (such as PMMA, thermoplastic polyimide, or LCP). Other materials which could be used to advantage as the fill material 18b in the present invention include solder mask, fluoropolymers, and other polymers and blends of polymers. The via fill material 18b also can be a composite polymeric material including particulate or fiber filler materials such as glass fibers, alumina, silicon carbide, magnesium oxide, or silicon dioxide (silica) particles to control thermal expansion or to increase thermal conductivity, where silica is particularly useful in mixtures to achieve a desired coefficient of thermal expansion. The via fill material also can include conductive fillers such as silver flake or metal particles including gold, copper and/or silver to improve conductivity and/or reliability. In yet some other applications, a via fill material can be an electrically conductive material—a metal such as copper or an alloy such as solder. The filler could include copper which has been plated sufficiently to completely fill the via. The solder filler could be created by printing solder paste into the vias, then reflowing to create a solder via fill.
The via fill material 18b can provide a mechanical strengthening of the electrical connection provided by the plated via. This via fill material reduces the stress on the via plating layer 18a during electrical connector operation, including reducing stress during thermal cycling or during activation of the electrical connector (for example, from flexing of the electrical connection structure or from expansion and contraction of the substrate 12). The present invention also contemplates that the via fill material might provide a sealed connector in some applications, including with a separate seal such as an o-ring, If desired. A sealed connector provided by (or in conjunction with) the via fill material can protect the sensitive electronic components inside of an electronic device from gases and liquids which might erode or corrode the electronic components and reduce the effectiveness and the useful life of the electronic system.
The via fill material 18b may be chosen based on the application under consideration. In some cases, it is desirable to have a coefficient of thermal expansion which is selected based on the coefficient of the plating material (approximately equal to that of the plating material). In other applications, it is desirable to have a coefficient of thermal expansion which is approximately the same as the coefficient of thermal expansion of the substrate. In still others, it is desirable to have a coefficient of thermal expansion which is approximately the average of the coefficients of thermal expansion of the plating material and the substrate.
The via fill material 18b might be thermally conductive in other applications. This can be accomplished by using thermally conductive fillers in the via fill material, such as metals (for example copper) and certain ceramic materials (for example boron nitride, aluminum nitride, or aluminum oxide). Using a thermally conductive fill material would improve the heat transfer through the electrical connector 10′ and reduce the heat retained at the electrical interconnections or transferred to the mating components, which may be heat sensitive. This can effectively increase the current carrying capacity of the connector, and as a result may reduce the number of high power interconnections required and/or improve the reliability of the system.
The via fill material 18b might be electrically conductive in certain other applications. This can be accomplished by including a metal (such as copper, silver, or gold) or a metallic alloy (such as solder) within the fill material. This type of material can reduce the electrical resistance through the electrical connector 10′, enabling high current carrying capability. This increased current carrying capacity can reduce the number of connector contacts (“pins” or “positions”) required to provide sufficient power to a device or system element. This can also reduce the heat generation due to resistive heating and can also improve signal integrity.
Because the elastic contacts commonly require surface finishing with a precious metal such as gold, to ensure low contact resistance and prevent corrosion, and the surface finishing frequently occurs subsequent to attachment of the contacts to the substrate, the via or plated through hole will typically incidentally be plated with the precious metal, increasing gold usage. The via fill material prevents the walls of the via from being plated with the precious metal, hence reducing precious metal usage and therefore fabrication cost.
In a connector structure where all of the vias are filled, the connector structure may be sealed from side to side and prevents moisture or water ingress through the connector structure. By sealing the perimeter of the connector to another component or element of the electronic system, a watertight connector can be achieved. This is a significant advantage, for example, for battery connectors for cell phones, where the battery side of the connector may have significantly higher likelihood of exposure to water than the electronic components within the main body of the phone housing. The sealed connector would prevent water ingress from the battery side of the connector into the main body of the phone, where sensitive electronic devices inside including semiconductor devices such as processor chips, memory chips, and logic chips reside.
The present invention is related to electrical connectors in general and is not limited to electrical connectors having a plurality of spring contacts on the top and bottom of the electrical connector, and it is not limited to a connector having electrical contacts on both top and bottom portions of the connector. So, in place of one set of the electrical contacts, an array of surface mount pads could be employed. In the alternative, the contacts could be a ball grid array (BGA), if desired,
Of course, it will be understood that many variations to this process are possible without departing from the spirit of the present invention. So, for example, if the fill material 18b does not substantially shrink during the cure process, planarization may be necessary (e.g., by mechanical abrasion) so that the hole fill 18b surfaces have the desired relationship to the surface of the substrate. If the fill material shrinks too much, then an additional fill step might be desired to bring the level of the fill material to the desired level. If it is desired to have the fill material 18b recessed from the surface of the substrate—for example, to prevent interference with the movement of the spring contacts), the surface of the substrate can be plated with copper in selected locations.
Finally, if some further finishing of the surface of the fill material is required or desired, it may be done, such as adding a metallization layer on top of the fill material (which can be accomplished through plating or other suitable methods).
Many modifications and alterations of the preferred embodiment described above are possible without departing from the spirit of the present invention. For example, the filled via can be created using a plating or etching process to create a copper or other metal post or pillar on the surface of a carrier sheet, and this post can be inserted into a hole in the non-conductive substrate material to create the solid or filled via. Further, some of the features of the present invention can be used to advantage without the corresponding use of other features. For example, the use of an abrasion of the fill of the vias may be desirable in some instances and not required in other instances. Accordingly, the foregoing description of the preferred embodiment should be considered as merely illustrative of the principles of the present invention and not in limitation thereof, as the claims which follow are the sole definitions of the present invention.
Claims
1.-23. (canceled)
24. An electrical connector comprising:
- a substrate having a first surface and a second surface and carrying electrical contacts on at least one surface and a plurality of apertures extending between the first surface and the second surface, said electrical contacts including an elastic portion;
- an electrically-conductive material which extends through at least one of the plurality of apertures and electrically couples the first surface and the second surface; and
- an additional material in addition to the conductive material which is included within at least one of the plurality of apertures, said additional material sealing at least a portion of the electrically-conductive material from exposure to the environment outside the substrate, said additional material chosen to have a coefficient of thermal expansion approximating the coefficient of thermal expansion of at least one of the substrate and the electrically-conductive material.
25. An electrical connector of the type described in claim 24 wherein the additional material is chosen to have a coefficient of thermal expansion between the coefficient of thermal expansion of the substrate and the coefficient of the electrically conductive material.
26. An electrical connector of the type described in claim 24 wherein the additional material includes a thermosetting epoxy material.
27. An electrical connector of the type described in claim 24 wherein the additional material is filled with silica particles.
28. An electrical connector of the type described in claim 24 wherein the additional material is filled with a material with high thermal conductivity.
29. An electrical connector of the type described in claim 24 wherein the additional material includes a fusible metal.
30. A method of making an electrical connector comprising the steps of:
- providing a connector substrate with a plurality of apertures;
- defining a plurality of electrically-conductive contacts on a flat sheet of conductive material, forming the flat sheet into a three-dimensional form with a plurality of elastic electrical contacts, attaching the three-dimensional conductive sheet with a plurality of electrical contacts to the substrate and singulating the electrical contacts;
- providing an electrically-conductive path through at least one of the apertures and attaching at least one of the electrical contacts to the electrically-conductive path through the substrate;
- choosing an additional material which has a coefficient of thermal expansion approximating the coefficient of thermal expansion of at least one of the substrate, the electrical contact and the electrically-conductive path; and
- inserting the chosen additional material into the aperture to protect the electrically-conductive path by providing a sealing of at least part of the electrically-conductive path.
31. A method including the steps of claim 30 wherein the step of filling includes the step of choosing a fill material with a characteristic based on at least one characteristic of the substrate.
32. A method including the steps of claim 30 wherein the step of filling includes the step of choosing a fill material with a characteristic based on at least one characteristic of the electrically conductive path.
33. A method including the steps of claim 30 wherein the step of filling includes the step of choosing a fill material with a characteristic based on at least one characteristic of at least one of the substrate, the electrical contact and the electrically conductive path through the substrate.
34. A method including the steps of claim 30 wherein the step of choosing a fill material includes the step of choosing a material with a suitable amount of silica included therein to provide the desired coefficient of thermal expansion.
35. An electrical connector comprising:
- a substrate including an insulating body, at least one mounting surface and a plurality of apertures extending at least partially through the substrate;
- a set of electrical contacts carried on the mounting surface of the substrate and at least some of the electrical contacts being proximate at least some of the apertures, the electrical contacts including at least one elastic spring contact;
- a first conductive material within at least some of the apertures and in contact with at least one of the electrical contacts providing an electrical path coupling the one electrical contact with a second surface of the substrate, said first conductive material only partially filling the apertures into which the first conductive material is within; and
- a second material in the same aperture in which the first conductive material has been inserted, said second material covering at least part of the first conductive material and filling at least part of the aperture, said second material having a coefficient of thermal expansion which approximates the coefficient of thermal expansion of at least one of the substrate and the first conductive material.
36. An electrical connector of the type described in claim 35 wherein the substrate has a second mounting surface comprising mounting pads for at least one chosen from solderballs and surface mount attachments, where at least one of the mounting pads is electrically connected to at least one of the electrical contacts.
37. An electrical connector of the type described in claim 35 wherein the second material comprises a thermosetting epoxy.
38. An electrical connector of the type described in claim 35 wherein the second material has a coefficient of thermal expansion which has been chosen based on the coefficient of thermal expansion of the first material.
39. An electrical connector comprising:
- a substrate having a first surface and a second surface and carrying electrical contacts on both surfaces and a plurality of apertures extending between the first surface and the second surface, said electrical contacts including an elastic portion;
- an electrically-conductive material which extends through at least one of the plurality of apertures and electrically couples the first surface and the second surface; and
- an additional material in addition to the conductive material which is included within each of the plurality of apertures, said additional material sealing the apertures to prevent ingress of fluid materials through the apertures;
- a sealing mechanism around the perimeter of at least the connector first surface, said sealing mechanism comprising a compliant material, said sealing mechanism providing a fluid ingress-inhibiting seal around the perimeter of the connector area containing the electrical contacts when compressed against a mating surface of an electrical component, such as a printed circuit board.
40. An electrical connector of the type described in claim 39 wherein the sealing mechanism comprises an O-ring.
41. An electrical connector of the type described in claim 39 wherein the sealing mechanism results from the use of a compliant coverlay material on the connector surface.
42. An electrical connector of the type described in claim 41 wherein the compliant coverlay material is comprised of an elastomer.
43. An electrical connector of the type described in claim 41 wherein the compliant coverlay material is comprised of a closed cell foam.
44. An electrical connector of the type described in claim 41 wherein the compliant coverlay material is comprised of an open cell foam which deters ingress of liquid when sufficiently compressed.
45. An electrical connector of the type described in claim 39 wherein a sealing mechanism is included on both surfaces of the connector.
46. An electrical connector comprising:
- a substrate including an insulating body, at least one mounting surface and a plurality of apertures extending at least partially through the substrate;
- a set of electrical contacts carried on the mounting surface of the substrate and at least some of the electrical contacts being adjacent to or on top of at least some of the apertures, the electrical contacts including at least one elastic spring contact;
- a first conductive material within at least some of the apertures and in contact with at least one of the electrical contacts providing an electrical path coupling the one electrical contact with a second surface of the substrate, said first conductive material only partially filling the apertures into which the first conductive material is within; and
- a second material in the same aperture in which the first conductive material has been inserted, said second material covering completely filling the apertures; and
- a sealing mechanism around at least the perimeter of at least the connector first surface, said sealing mechanism comprising a compliant material, said sealing mechanism providing a seal which inhibits the ingress of liquids from around the perimeter of the connector area containing the electrical contacts when compressed against a mating surface of an electrical component, such as a printed circuit board.
Type: Application
Filed: Feb 4, 2014
Publication Date: Jun 5, 2014
Applicant: Neoconix, Inc. (Sunnyvale, CA)
Inventors: David Noel Light (Los Gatos, CA), Dinesh Sundararajan Kalakkad (Palo Alto, CA), Peter Tho Nguyen (San Jose, CA)
Application Number: 14/172,664
International Classification: H01R 35/02 (20060101); H05K 1/11 (20060101); H01R 13/52 (20060101);