IMPEDANCE MATCHED VIA CONNECTIONS IN A PRINTED CIRCUIT BOARD
20240074054 ยท 2024-02-29
Inventors
Cpc classification
H05K1/0296
ELECTRICITY
H05K1/0222
ELECTRICITY
H05K1/0251
ELECTRICITY
H05K1/115
ELECTRICITY
International classification
Abstract
Vertical launch impedance matched through-hole vias to ensure proper impedance matching is maintained after a printed circuit board connector is attached to a printed circuit board. A conductive via having a center aperture and a via body having a slot adjacent either the via top surface and/or via bottom surface, and a dielectric component insertable within the via center aperture, and having a slot aligned with the conductive via body slot. The dielectric component having a center aperture with a conductive member in electrical communication with a PCB signal trace without contact to the conductive via. A printed circuit board connector having a center signal pin with a slotted dielectric component attached thereto, or a slotted dielectric component in conjunction with a slotted, conductive via body attached thereto.
Claims
1. An apparatus for conducting an electrical signal between a first conductive strip of a printed circuit board and a printed circuit board connector, said apparatus comprising: a via having a via body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the inside wall forms a via body center through-hole, and wherein said via body includes an aperture or slot adjacent either the via body top surface or via body bottom surface, or said via body includes at least two apertures or slots, wherein a first aperture or slot is adjacent the via body top surface and a second aperture or slot is adjacent the via body bottom surface; and a dielectric component having a body defining a dielectric component inside wall, an outside wall, a top surface, and a bottom surface, said dielectric component body sized for insertion within said via body center through-hole, said dielectric component body including a center through-hole coaxial with said via center through-hole, and wherein said dielectric component body includes an aperture or slot adjacent either the dielectric component top surface or dielectric component bottom surface, or said dielectric component body includes at least two apertures or slots, wherein a first dielectric component aperture or slot is adjacent the dielectric component top surface and a second dielectric component aperture or slot is adjacent the dielectric component bottom surface; such that said via body aperture or slot is aligned with said dielectric component aperture or slot when said dielectric component is inserted within said via center through-hole.
2. The apparatus of claim 1 wherein said via body aperture or slot comprises a gap or hole extending from said via body inside wall to said via body outside wall.
3. The apparatus of claim 1 wherein said dielectric component aperture or slot comprises a gap or hole extending from said dielectric component inside wall to said dielectric component outside wall, and into said dielectric component center aperture or through-hole.
4. The apparatus of claim 1 wherein said via body and said dielectric component are mounted within said printed circuit board.
5. The apparatus of claim 1 wherein said dielectric component includes a plurality of dielectric materials.
6. The apparatus of claim 1 wherein said via body is cylindrical having an outer diameter, and includes a ring on said via body bottom surface or said via top surface or both, said ring having an outer diameter greater than said via body outer diameter, such that said ring extends beyond said via body outer diameter in a radial direction.
7. The apparatus of claim 6 wherein said ring includes an aperture or slot extending therethrough such that said ring aperture or slot is aligned with said via body aperture or slot.
8. The apparatus of claim 1 wherein said via body and said dielectric component are within said printed circuit board such that said via body top surface and said dielectric component top surface are approximately flush with a top surface of said printed circuit board.
9. The apparatus of claim 1 wherein said via body includes conductive material, such that said via body is capable carrying electrical current.
10. The apparatus of claim 9 wherein said via body is formed of a non-conductive material plated with said conductive material.
11. The apparatus of claim 1 wherein said via body is fabricated during PCB fabrication on a layer-by-layer basis and/or said dielectric component is placed within said via body during said PCB fabrication.
12. The apparatus of claim 1 wherein said via body center through-hole and said dielectric component center through-hole are coaxial and extend through said PCB.
13. The apparatus of claim 1 wherein said via body and said dielectric component are situated within said PCB such that top and bottom surfaces of said via body and said dielectric component are not exposed to both a top surface of said PCB and a bottom surface of said PCB.
14. The apparatus of claim 1 wherein said via body and said dielectric component are situated within said PCB such that a top surface of said via body and said dielectric component are not exposed to a top surface of said PCB, or a bottom surface of said via body and said dielectric component are not exposed to a bottom surface of said PCB.
15. The apparatus of claim 1 wherein said via body and said dielectric component are situated within said PCB such that top and bottom surfaces of said via body and said dielectric component are not exposed to either a top surface of said PCB or a bottom surface of said PCB, and including: a second via having a second body defining a second inside wall, a second outside wall, a second top surface, and a second bottom surface, wherein the second inside wall forms a second via body center through-hole, and wherein said second via body includes an aperture or slot adjacent either the second via body top surface or second via body bottom surface, or said second via body includes at least two apertures or slots, wherein an upper aperture is adjacent the second via body second top surface and a lower aperture is adjacent the second via body second bottom surface; and a second via dielectric component having a second dielectric component body defining a second dielectric component inside wall, a second dielectric component outside wall, a second dielectric component top surface, and a second dielectric component bottom surface, said second dielectric component body sized for placement within said second via body center through-hole, said second dielectric component body including a center through-hole coaxial with said second via body center through-hole, and wherein said second dielectric component body includes an aperture or slot adjacent either the second dielectric component top surface or second dielectric component bottom surface, or said second dielectric component body includes at least two apertures or slots, wherein an upper dielectric component aperture or slot is adjacent the second dielectric component top surface and a lower dielectric component aperture or slot is adjacent the second dielectric component bottom surface; such that said second via body apertures or slots are aligned with said second dielectric component apertures or slots when said second dielectric component is inserted within said second via body center through-hole; and wherein said second via body and said second dielectric component are situated within said PCB such that top and bottom surfaces of said second via body and said second dielectric component are not exposed to a top surface of said PCB or a bottom surface of said PCB.
16. A printed circuit board connector having a bottom surface for connection to a printed circuit board, said connector comprising: a connector center conductor for transmitting an electrical signal; a dielectric component having a body defining a dielectric component inside wall, an outside wall, a top surface, and a bottom surface, said dielectric component body including a center through-hole, wherein said connector center conductor is inserted within said dielectric component body center aperture or through-hole.
17. The printed circuit board connector of claim 16 wherein said dielectric component body includes an aperture or slot adjacent either said dielectric component top surface or bottom surface or both.
18. The printed circuit board connector of claim 16 including a conductive via body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the inside wall forms a via through-hole.
19. The printed circuit board connector of claim 17 including a conductive via body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the inside wall forms a via through-hole, wherein said via body includes an aperture or slot adjacent either the via body top surface or via body bottom surface or both, such that said dielectric component body is situated within said via body center through-hole, and wherein said via body aperture or slot is aligned with said dielectric component aperture or slot when said dielectric component is inserted within said via center through-hole.
20. The printed circuit board connector of claim 16 including a plurality of prongs extending below said printed circuit board connector bottom surface for attachment to the printed circuit board, said plurality of prongs forming a mechanical support for said printed circuit board connector.
21. The printed circuit board connector of claim 20 wherein said plurality of prongs are in electrical communication with said ground or zero potential contact or line of said printed circuit board, and/or in electrical communication with at least one via body in said printed circuit board.
22. A printed circuit board (PCB) connector assembly having a plurality of PCB connectors, each having a bottom portion for connection to a printed circuit board, at least one of said plurality of PCB connectors comprising: a connector center conductor for transmitting an electrical signal; a dielectric component having a body defining a dielectric component inside wall, an outside wall, a top surface, and a bottom surface, said dielectric component body including a center through-hole, wherein said connector center conductor is located within said dielectric component body center aperture or through-hole.
23. The printed circuit board connector assembly of claim 22 wherein said dielectric component body includes an aperture or slot adjacent either said dielectric component top surface or bottom surface or both.
24. The printed circuit board connector assembly of claim 22 including a conductive via body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the inside wall forms a via through-hole.
25. The printed circuit board connector assembly of claim 23 including a conductive via body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the inside wall forms a via through-hole, wherein said via body includes an aperture or slot adjacent either the via body top surface or via body bottom surface or both, such that said dielectric component body is situated within said via body center through-hole, and wherein said via body aperture or slot is aligned with said dielectric component aperture or slot when said dielectric component is inserted within said via center through-hole.
26. The printed circuit board connector assembly of claim 22 wherein at least one of said plurality of PCB connectors includes a PkZ? connector.
27. The printed circuit board connector assembly of claim 22 wherein said plurality of PCB connectors are in the form of a square array, rectangular array, circular array, or polygon array.
28. The printed circuit board connector assembly of claim 22 wherein a footprint of said PCB connector assembly is in the form of a square, rectangle, circle, or polygon shape.
29. A printed circuit board electrical connection assembly comprising: a printed circuit board (PCB) having a top surface, a bottom surface, and an interior therebetween, wherein said PCB includes a signal line and a ground or zero potential contact or line; a via insertable within or formed within said PCB, said via having a via body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the inside wall forms a via center through-hole, and wherein said via body includes an aperture or slot adjacent either the via body top surface or via body bottom surface, or said via body includes at least two apertures or slots, wherein a first aperture is adjacent the via body top surface and a second aperture is adjacent the via body bottom surface, wherein said via body is conductive for transmitting electrical signals or for providing a ground or zero potential, and wherein said via body extends into said PCB interior; and a dielectric component having a body defining a dielectric component inside wall, an outside wall, a top surface, and a bottom surface, said dielectric component body sized for placement within said via body center through-hole, said dielectric component body including a center through-hole coaxial with said via center through-hole, and wherein said dielectric component body includes an aperture or slot adjacent either the dielectric component top surface or dielectric component bottom surface, or said dielectric component body includes at least two apertures, wherein a first dielectric component aperture is adjacent the dielectric component top surface and a second dielectric component aperture is adjacent the dielectric component bottom surface, and wherein said dielectric component apertures align with said via body apertures when said dielectric component is inserted within said via body center through-hole; and a conductive trace and/or solder bridge formed on or within said PCB and traversing through said dielectric component aperture or slot and through said via body aperture or slot to said dielectric component center through-hole without making electrical contact with said via body.
30. The printed circuit board electrical connection assembly of claim 29 wherein said via apertures or slots extend from said via body inside wall to said via body outside wall.
31. The printed circuit board electrical connection assembly of claim 30 wherein said dielectric component apertures or slots extend from said dielectric component inside wall to said dielectric component outside wall, and into said dielectric component center aperture or through-hole.
32. The printed circuit board electrical connection assembly of claim 29 wherein said via body is cylindrical having an outer diameter, and includes a ring on said via body top or bottom surface, or both said top and bottom surface, said ring having an outer diameter greater than said via cylindrical body outer diameter, such that said ring extends beyond said via cylindrical body in a radial direction, and wherein said ring includes said via body aperture or slot extending therethrough such that said ring aperture or slot aligned with said via body aperture or slot.
33. The printed circuit board electrical connection assembly of claim 32 wherein said conductive trace and/or solder bridge extends through said ring aperture or slot.
34. The printed circuit board electrical connection assembly of claim 29 wherein said dielectric component center through-hole includes a conductive member in electrical communication with said conductive trace and/or solder bridge.
35. The printed circuit board electrical connection assembly of claim 29 wherein said via body top surface and said dielectric component top surface are approximately flush with said printed circuit board top surface.
36. The printed circuit board electrical connection assembly of claim 29 wherein said dielectric component conductive member includes a contact pin that extends beyond said dielectric body top surface.
37. The printed circuit board electrical connection assembly of claim 29 wherein said dielectric component conductive member includes an electrical pin socket that extends beyond said dielectric body top surface.
38. The printed circuit board electrical connection assembly of claim 29 wherein said dielectric component conductive member includes an electrical pin socket that is approximately flush said dielectric component body top surface, and extends below said dielectric component top surface.
39. The printed circuit board electrical connection assembly of claim 29 wherein said via is located entirely within said printed circuit board interior, or extends from said printed circuit board top or bottom surface into said printed circuit board interior.
40. The printed circuit board electrical connection assembly of claim 32 wherein said via is located within said printed circuit board interior, or extends from said printed circuit board top or bottom surface into said printed circuit board interior.
41. The printed circuit board electrical connection assembly of claim 33 wherein said via is located within said printed circuit board interior, or extends from said printed circuit board top or bottom surface into said printed circuit board interior.
42. The printed circuit board electrical connection assembly of claim 37 wherein said via is located within said printed circuit board interior, or extends from said printed circuit board top or bottom surface into said printed circuit board interior.
43. The printed circuit board electrical connection assembly of claim 38 wherein said via is located within said printed circuit board interior, or extends from said printed circuit board top or bottom surface into said printed circuit board interior.
44. A printed circuit board connection assembly for conducting an electrical signal between a conductive strip of a printed circuit board and a printed circuit board connector, said assembly comprising: a printed circuit board (PCB) having a top surface, a bottom surface, and an interior therebetween, wherein said PCB includes a signal trace and/or a ground trace; a via having a body defining an inside wall, an outside wall, a top surface, and a bottom surface, wherein the via body inside wall forms a via body center through-hole, and wherein said via body includes an aperture or slot adjacent either the via body top surface or via body bottom surface or both, and wherein at least a portion of said via body is electrically conductive; and a dielectric component having a body defining an inside wall, an outside wall, a top surface, and a bottom surface, said dielectric component body sized for placement within said via body center through-hole, said dielectric component body including a center through-hole coaxial with said via body center through-hole, said dielectric component center through-hole supporting a conductive member, wherein said dielectric component body includes an aperture or slot adjacent either said dielectric component top surface or bottom surface or both, and wherein said via body aperture or slot is aligned with said dielectric component aperture or slot when said dielectric component is placed within said via body center aperture; a conductive trace and/or solder bridge formed on or within said PCB and traversing through said dielectric component aperture or slot and said via body aperture or slot to said dielectric component center through-hole without making contact with said via body, and in electrical communication with said dielectric component center through-hole conductive member.
45. The printed circuit board connection assembly of claim 44 including: a printed circuit board connector having a bottom surface, a center conductor for carrying an electrical signal line, and an outer conductor carrying a ground line, wherein said signal line is in electrical communication with said dielectric component center through-hole conductive member.
46. The printed circuit board connection assembly of claim 45 wherein said printed circuit board connector center conductor forms a contact pin or socket that extends beyond said printed circuit board connector bottom surface.
47. The printed circuit board connection assembly of claim 46 wherein said printed circuit board connector center conductor is insertable within said dielectric component through-hole upon connection to said printed circuit board.
48. The printed circuit board connection assembly of claim 45 wherein said dielectric component center through-hole conductive member extends through said dielectric from said dielectric top surface to said dielectric bottom surface.
49. The printed circuit board connection assembly of claim 46 wherein said dielectric component conductive member includes a pin socket that is approximately flush with or below said dielectric component body top surface, and receives said printed circuit board connector center conductor contact pin.
50. The printed circuit board connection assembly of claim 45 wherein said printed circuit board connector center conductor forms a pin socket that is approximately flush with said printed circuit board connector bottom surface.
51. The printed circuit board connection assembly of claim 46 wherein said dielectric component conductive member includes a contact pin that extends beyond said dielectric body top surface and is insertable within said printed circuit board connector center conductor pin socket.
52. The printed circuit board connection assembly of claim 45 wherein said printed circuit board connector center conductor forms a contact pin that is approximately flush with said printed circuit board connector bottom surface.
53. The printed circuit board connection assembly of claim 52 wherein said dielectric component conductive member includes an electrical pin socket that extends beyond said dielectric body top surface.
54. The printed circuit board connection assembly of claim 45 wherein said printed circuit board connector includes a plurality of prongs extending below said printed circuit board connector bottom surface.
55. The printed circuit board connection assembly of claim 54 wherein said plurality of prongs are in electrical communication with said ground or zero potential contact or line of said printed circuit board.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:
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DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0088] In describing the preferred embodiment of the present invention, reference will be made herein to
[0089] To mitigate the effects of a lossy connection, various via designs are presented. These via designs generally comprise a well-designed electrical insulating material, such as materials with dielectric properties, e.g., Teflon and the like, or materials which will assist after connection to maintain electrical separation, and an impedance match between the installed PCB connector and the PCB signal lines or traces. For this purpose, as will be discussed in greater detail below, a slotted through-hole via body is designed and a slotted dielectric is employed in conjunction therewith, where the slots are aligned. The slots are essentially holes or apertures in their respective components, that allow a gap or break in the components in order to effectuate signal transmission. Slots, holes, or apertures may be used interchangeably to describe this aspect of the slotted configuration forming the external portion of the slotted via body and/or slotted dielectric.
[0090] The purpose of the slots is to establish a connection bridge between the connector center signal pin and the signal line or trace on the PCB without shorting the signal to ground, and while maintaining a constant or near-constant impedance match. When the connector is placed perpendicular to the board into the via (e.g., in a vertical launch design) with a well-designed insulating material (dielectric), desired matched impedance (e.g., 33, 50, 75 ohms) can be readily achieved. To attain such a matched impedance circuit, the through-hole via diameter, insulating material, and connector pin configuration are calculated and adjusted.
[0091] The size of the via hole, and the material used for the via dielectric and/or pin or socket, are based on the impedance formula (for a single material dielectric):
[0097] The dielectric material may be chosen based on its efficiency for electrostatic fields and poor conductivity. There are many dielectric materials that can be used to create an impedance match, including in some instances, a dielectric produced by an air gap.
[0098] Connectors in a vertical launch construction can be mounted on the top or bottom of a PCB. Given the geometric construct, the attachment of a vertical launch connector is in a direction perpendicular to the PCB top (or bottom) surface with a via extending through the PCB surface. The center contact leg of the PCB connector makes electrical contact to a signal trace by way of the via. In a preferred embodiment, the via is conductive so that there is an electrical connection with the via and ground or zero potential. This conduction may be in the form of a conductive plating on an otherwise non-conductive surface of a component. The connector generally includes longitudinally extending legs which are inserted into the PCB, and which present mechanical stability for the attaching connector to the PCB, and may provide electrical connection to ground by way of ground vias or traces in the PCB. This design increases the number of connectors on a PCB versus an end launch connection scheme, and provides greater mechanical strength than end launch connectors.
[0099] Typically for a vertical launch connection, a signal trace and via are connected by design, wherein the connector center contact is either soldered within the via or electrically connected by other means, and the signal trace connects directly to the via as well. It is the via that makes electrical connection with the PCB signal trace. In contrast, in at least one embodiment of the present invention, distinguishing itself from the prior art, the via inner walls and signal trace are not in electrical contact. In such an embodiment, a slotted dielectric component surrounds the center contact pin of the PCB connector, electrically separating the center contact pin from the via inner wall. However, in order to achieve electrical contact between the center contact pin and the signal trace on the PCB, corresponding gaps, slots, or apertures are established in the via body and the dielectric respectively, which are then aligned upon installation.
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[0101] Dielectric component 50 has a diameter D.sub.1, and includes a cylindrical disc 56 formed on its top surface, and having a diameter greater than D.sub.1, so that cylindrical disc 56 extends radially beyond the cylindrical body of dielectric component 50 that is insertable into the slotted via body via 60. Within PCB 58 is a conductive, slotted via body 60, which may be formed during the PCB fabrication process or may be inserted as a solid construct. The conductive body may be formed of a non-conductive material, plated with a conductive coating. Slotted via body 60 includes a slot 62, which is ultimately aligned with slot 52 of dielectric component 50 upon insertion. Dielectric component 50 is inserted within, and coaxial with, slotted via body 60 center through-hole 64.
[0102] In this embodiment, generally a board designer would specify the dimensions of the components for impedance matching. In a preferred installation, the board designer/manufacturer would produce and assemble the embodiment of
[0103] As depicted, the vias described herein, implementing the present invention, may be fabricated using printed circuit board technology stated in the art. Thus, it is possible for the via to be a single construct insertable within a PCB, or formed from a multitude of PCB layers during fabrication. In either manner, a slotted, conductive via body, capable of receiving a dielectric component, is the resultant configuration that can be utilized to practice embodiments of the present invention.
[0104] Slotted via body 60 is preferably plated with a conductive coating or fabricated of a solid conductive material. In the illustrative embodiment, the outer diameter of cylindrical disc or ring 56 is less than the inner diameter of the center through hole opening 64 of slotted via body 60, but greater than an inner diameter of an inner wall 68 of slotted via body 60, such that in at least one embodiment, cylindrical disc 56 is seated within an annular collar located at the top portion of slotted via body 60, allowing the dielectric component top surface to be approximately planar with the top surface 70 of PCB 58.
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[0108] In order for a center contact to work in this via embodiment, it must be coated or protected with an insulator, otherwise the center contact would be in electrical contact with the slotted via body inner wall, which would short circuit the signal line 74. This dielectric or insulating coating or covering must also include an uncovered portion or slotted portion 52 that coincides with the location of slot 62 to establish electrical connection of the center contact with the PCB signal trace. In different embodiments, this coating or covering is in the form of a cylindrical dielectric component having a center channel for receiving the center contact, and a slot preferably located at the signal line location of the dielectric component, aligned with a similar slot on the slotted via body, allowing for electrical contact from the center contact to a PCB trace line. A connection bridge is needed to connect one end of signal trace 74 to a center contact within aperture 54, through slots 52, 62.
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[0110] The aforementioned embodiment presents a slotted, electrically conductive via body, generally in electrical communication with ground or other reference potential, which is contrary to the prior art designs. The ground component (via body) may be depicted as a ring extending radially outwards away from the outer diameter of the cylindrical body of the dielectric component. This ring includes a gap or slot at least at one end to allow a trace line or connection bridge to traverse radially inwards towards a center contact located coaxial with the dielectric component.
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[0112] In this embodiment, generally a board designer would specify the dimensions of the components for impedance matching. In a preferred installation, the board designer/manufacturer would produce and assemble the embodiment of
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[0114] Thus, even though conductive, slotted via body 60 encompasses dielectric component 50, and dielectric component 50 shields signal center conductor 78 from shorting against the conductive slotted via body 60, the slotted portions allow for a signal trace to be in electrical communication with the signal center conductor 78 without shorting to the slotted via body. As shown, slot 62 of slotted via body 60 is aligned with dielectric component slot 52 of dielectric component 50.
[0115] In the illustrative embodiment, slotted dielectric component 50 includes a cylindrical disc or ring 56 at its top end having an outer diameter greater than the outer wall of the cylindrical body of slotted dielectric component 50. The outer diameter of cylindrical disc or ring 56 is also less than the inner diameter of the hole opening 64 of slotted via body 60, but greater than an inner diameter of an inner wall 68 of slotted via body 60, such that in at least one embodiment, cylindrical disc or ring 56 is seated within an annular receiving portion at one end of the slotted via body 60, and is approximately planar with the top surface 70 of PCB 58.
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[0117] Slotted via body 60 encompasses a slotted dielectric component 50, which includes a center conductor, socket contact extension 84 with socket 84a that extends longitudinally upwards and connects with a signal conductor on a PCB connector (not shown) outside the PCB. In this embodiment, the extended socket 84a outside the PCB connects with a center conductor of a PCB connector, such as PCB connector 170 of
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[0124] In an alternate embodiment, an extended portion of a signal line may extend underneath the via until it reaches a center channel where electrical contact can be made to a conductive member inserted within channel. In yet another embodiment, instead of adding an insulator, the outer wall of the via body may be shortened near the signal line, such that an air gap is formed between the via body and the signal line.
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[0127] Design Implementations for Different Types of Slotted Vias
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[0129] A blind via 112 connects an outer layer of the board to inner layers and does not go through the entire board. A buried via 114 connects inner layers without reaching the outer layers. And a through hole via 110 goes all the way through, from top to bottom, touching all adjacent layers. Staggered Vias (e.g., combination of via 112 and 114) are the most common and economical form of microvias. However, staggered microvias require more space as a result of not being built around the same core.
[0130] Stacked vias are used if, for example, an essential blind via exceeds an aspect ratio of 1:1 phasing out sequential lamination due to a new blind via starting on the same layer that the aforementioned blind via ends. A stacked via consists of multiple vias layered directly on top of each other. Typically, each via is first drilled and then metalized, leaving a small annular ring at the top and bottom to ensure electrical connection. Because one via can be placed on top of another, stacked vias take up less space on a PCB than through-hole via. This makes successful routing of high-density boards more practical and flexible. Good use of stacked vias allows full flexibility in layer connectivity. It also reduces the parasitic capacitance typically associated with via.
[0131] Many PCB boards are small and have a limited amount of space, so the blind and buried vias can provide additional room and options for the board. The buried vias, for example, will help to free up space on the surface of the board without affecting the surface components or traces that are on the top or bottom layers. The blind vias can help to free up some additional space. They are often used for fine pitch BGA components. Since the blind vias only go through a portion of the board, it also means that there will be a reduction of signal stubs.
[0132] Blind vias are common in high-density interconnect (HDI) PCBs. The added complexity of blind vias allows designers to improve signal integrity while reducing PCB size. Using blind vias presents a range of new routing alternatives and options as valuable space is no longer needed for through-hole vias, which travel through layers where they are not connected to.
[0133] While the blind and buried vias can be used with many various PCBs, they tend to be used most often for high-density interconnect PCBs.
[0134] Referring to
[0135] Buried via 114 depicts slotted portions that may be designed on the top and/or bottom ends of the via. Shown is a construction of a buried via incorporating the salient features of at least one embodiment of the present invention. Buried via 114 is situated at a certain depth within the PCB, generally a predetermined number of layers within the PCB, such that the buried via does not extend through the board on either side. This type of via may include an air layer, PCB material, or other dielectric material with respect to its placement in the PCB. A signal layer or trace is embedded within the PCB, and in electrical communication with an electrical conductor within the slotted dielectric component. The signal layer or trace connects through the slotted apertures of the via body and dielectric component to a center contact pin (not shown).
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[0137] Stacked via 116 is shown cutting through three PCB layers, and presents three different dielectric component embodiments of the present invention. In the topmost via of the stacked combination (A), the conductive, slotted via body and slotted dielectric component 117 design are common to those presented in
[0138] PCB Connector Schemes
[0139] Different connector schemes may be employed to accommodate the above-identified slotted via body and slotted dielectric component designs. In some embodiments, an external dielectric PkZ? connector may be utilized having a slotted dielectric component attached thereto. A PkZ? connector, such as that designed and manufactured by the Phoenix Company of Chicago, accommodates large radial and axial misalignment tolerances found in modular applications. PkZ? technology does not require full mating to achieve constant impedance, eliminating elaborate methods such as an internal spring to overcome mating gaps and guarantee full mating.
[0140] Impedance changes in a typical coaxial connector interface as a gap is introduced due to typical and expected changes in the ratio of conductors and the dielectric constant. PkZ? designs provide constant impedance even as differences in mating profiles or gaps are created in the mating interface.
[0141] The inner and outer contacts of a male connector plug and a female connector plug are of predetermined shape, and the material for the dielectric is chosen, such that when the male connector plug is engaged with the female connector plug, along the central axis of the engaged connection, the effective outer diameter of the inner contact referenced by d, the effective inner diameter of the outer contact referenced by D, and the relative dielectric constant of the medium therebetween referenced by ?, satisfy the above-identified equation for impedance Z. The geometry is determined and the dielectric material selected so that anywhere along the central axis of the connector the impedance is substantially constant. In this manner, a constant impedance connector allows for tolerances in the connector housings that may otherwise degrade electrical performance of the connectors.
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[0150] Conductive, slotted via body 138a and cylindrically inserted dielectric component 136a are attached to the PCB 142 of
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[0163] The advantages of a vertical launch impedance matched via of the present invention include: a) maintaining impedance matching between the PCB connector and the PCB after installation; b) allowing for high frequency range capabilities; c) allowing for a vertical assembly configuration; d) allowing for through-hole soldering, thus creating a stronger bond between components and the PCB; e) increasing density of connections on the PCB; f) accommodating larger components that may undergo high power, high voltage, and mechanical stress, such as transformers, connectors, semiconductors, and electrolytic capacitors; and g) being capable of withstanding greater environmental stress.
[0164] The employment of the through-hole vertical launch impedance matched via of the present invention mitigates the lossy effects of PCB connections. A matched impedance is calculated and adjusted by configuring a via having a predetermined diameter, selected material and pin configuration, utilizing the impedance formula described below.
[0165] Test results characterizing the improvement made to a signal when a proper 50-ohm impedance matched through-hole was used between a PCB connector and a PCB. Comparing the traces, there is a significance improvement in the loss performance of the circuit with the matched via after dielectric installation versus a soldered via without any dielectric present. Though, both circuits loss performance is similar at initial frequencies, the traditional signal via performance degrades with frequency. An empirically measured 10 dB loss performance improvement is seen after 11 GHz frequency when a matched via with dielectric is used.
[0166] While the present invention has been particularly described, in conjunction with a specific preferred embodiment, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present invention.
[0167] Thus, having described the invention, what is claimed is: