Patent Application
20050174745
1. Field of the Invention
The present invention relates to an electronic assembly comprising a substrate element having a mounting surface, circuitry disposed on the mounting surface, and an edge surface distinct from the mounting surface.
2. Description of the Related Art
The electronic assembly 2 also comprises an external antenna 18 that is connected to the circuitry disposed on the mounting surface 6 of the substrate element 4 with a cable 22 and connector 20.
For many applications, the circuitry disposed on the substrate element 4 can be made to be very small, but the circuitry can be dwarfed by the size of the antenna 16. Thus the antenna becomes the largest part of the radio frequency communication link. Furthermore, the cable 22 and connector 20 are bulky and expensive.
It is therefore desirable to minimise the volume occupied by the radio frequency communication circuitry including the antenna. This is particularly true for short-range applications such as mobile phones, pagers and medical applications.
Instead of using an external antenna 18 such as that shown in
It is therefore desirable to provide an electronic assembly in which the above-mentioned disadvantages are overcome.
U.S. Pat. No. 4,577,195 discloses a miniaturized mobile radio receiver having two printed circuit boards disposed in a housing, with a wire portion on each printed circuit board forming two halves of a dipole antenna. The base of the antenna is located on either printed circuit board. The wires are disposed on the main face of their respective printed circuit boards towards the periphery of the board.
Each of GB-A-2248345, JP-A-11274669, U.S. Pat. No. 4,539,747 and U.S. Pat. No. 3,398,232 can be considered to disclose an electronic assembly having a conductive track extending from circuitry on a mounting surface onto and along an edge surface surrounding the mounting surface, for various different purposes. In GB-A-2248345, the conductive tracks on the edge surface are electroplated channels, which are concave shaped to partially embrace wire leads extending vertically downward from a display board placed on top of the printed circuit board, which are then soldered to the electroplated channels. In JP-A-11274669, the conductive track is an edge circuit which is provided for heat dissipation purposes. In U.S. Pat. No. 4,539,747, the conductive tracks are conductive “ribs” which are provided as an electrical connection between two surfaces of a printed circuit board. In U.S. Pat. No. 3,398,232, the conductive tracks are provided for the same purpose as those in U.S. Pat. No. 4,539,747.
An embodiment of one aspect of the present invention provides an electronic assembly comprising a substrate element having a mounting surface. Circuitry is disposed on the mounting surface. An edge surface is at the periphery of and distinct from the mounting surface. An electrically-conductive track extends from the circuitry along at least part of the edge surface to form at least one electronic component.
The mounting surface may be substantially planar.
The edge surface may form an angle with the mounting surface where the surfaces meet.
The edge surface may be substantially normal to the mounting surface where the surfaces meet.
The conductive track may extend along the edge surface in a direction substantially parallel to the nearby mounting surface.
The substrate element may be substantially cuboidal, with one surface of the cuboid forming the mounting surface and the four side surfaces of the cuboid adjacent the, mounting surface collectively forming the edge surface. The conductive track may extend along at least two of the four side surfaces. The conductive track may extend along at least three of the four side surfaces. The conductive track may extend along all of the four side surfaces.
The conductive track may form at least one complete turn around the edge surface.
The conductive track may form a number of turns around the edge surface in a helical shape.
The substrate element may be uniformly formed of a non-conductive material. The non-conductive material may be alumina.
The substrate element may be a printed circuit board.
The substrate element may be a semiconductor wafer.
At least part of the circuitry may be formed on the substrate element by a thick film printing process.
The conductive track may be arranged to form an antenna. The circuitry may comprise a radio frequency electronic component. The conductive track may be arranged to form a helical antenna as one or more of the at least one electronic components.
The conductive track may be open-ended.
Alternatively the conductive track may extend from the edge surface back to the mounting surface to form a closed loop. The conductive track may extend back to the circuitry using a via hole through the substrate element.
The conductive track may be arranged so as not to intersect itself.
The conductive track may extend back to the circuitry using a return path extending over or under the outward path conductive track, with an electrically-insulating layer in between.
The conductive track may be arranged to form an inductive element as one or more of the at least one electronic components.
The conductive track may be arranged to form a resistive element as one or more of the at least one electronic components.
The conductive track may be formed by a thick film printing process.
The substrate element may be thin or wafer-like so that the edge of the substrate element forms the edge surface. A lateral dimension of the mounting surface may be at least 30 times the thickness of the substrate element. A lateral dimension of the mounting surface may be at least 60 times the thickness of the substrate element.
Unlike the previously-considered electronic assemblies described above, where the antenna component 18 is either provided as a separate item (usually bulky) or printed on the mounting surface of the substrate, in an embodiment of the present invention the edge surface 36 of the substrate 32 is employed for this purpose. As shown in
Thick film printing uses ink that is hard when cured and is a good electrical conductor, and gold is one example of the electrically-conducting material that can be used. The ink is applied through a fine mesh with the area to be printed being defined by a pattern on the mesh. Once applied, the alumina substrate element 32 is heated to a predetermined temperature for a specific period of time, and this causes the ink to solidify and form a solid conductive track. The thick film printing process will be well known to those familiar with the art.
In one particular embodiment, the electronic assembly 30 is arranged to provide a 400 MHz transmitter. The alumina substrate element 32 has a width W of 3 cm, a height H of 3 cm and a thickness T of 1 mm. With these dimensions, the thick film printing process used can allow the formation of about two turns of gold conductive track 40 printed on the edge surface 36 of the substrate 32.
The use of the edge surface 36 of the substrate element 32 results in a highly efficient use of available substrate area, and frees up the valuable and limited area on the mounting surface 34 of the substrate 32 as compared to the previously-considered scheme of printing a patch antenna onto the mounting surface 34. The overall size of the electronic assembly 30 is also much reduced as compared to the previously-considered scheme where a separate and bulky antenna element is employed.
The embodiment described above with reference to
Although the above embodiments show a substrate element 32 which is substantially cuboidal and has a substantially rectangular or square mounting surface 34, it will be appreciated that any shaped substrate element can be used, for example a circular substrate. Similarly, although the mounting surface 34 in the above embodiment is substantially planar, this is not essential. In the above embodiments, the edge surface 36 is distinct from the mounting surface 34 in that the two surfaces meet at an angle. Although it will usually be the case that the edge surface 36 is substantially normal to the mounting surface 34 where the surfaces meet, it will be appreciated that this is not essential. It is also preferred, but not essential, that the conductive track 40 extends along the edge surface 36 in a direction substantially parallel to the nearby mounting surface 34; other shapes of conductive track will also serve the function.
Although the preferred embodiments have a helical antenna arrangement, any other type of antenna shape can be formed on the edge surface 36. For example a dipole, coil, fractal or whip antenna shape is also possible. In addition, an electronic assembly embodying the present invention may be used with or without a ground plane.
An alternative to printing onto an alumina substrate element is to start with an alumina substrate element coated with conductor and then etch away unwanted conductor. This is known as the thin film process. Copper, gold, silver, nicrome alloy or other types of conductor can be used in such a process. The substrate element can be coated on any number of available sides.
Printed circuit board (PCB) is a common medium for electronic and radio frequency circuits, and the substrate element 36 can be of this type instead of being an alumina substrate. An etching process is usually used with printed circuit boards. Other types of substrate include ferrite, Duroid (trademark), glass, alumina with various impurities, or any other type of insulating material. The substrate element may also be formed from a semiconductor material.
The main application of an edge-printed conductive track described above is for use as an antenna. However, it will be appreciated that the edge-printed track can be used in a corresponding manner to form other types of electronic component such as an inductor or a resistor. Tracking merely for the purpose of providing an electrical connection between two circuitries is not considered to be an “electronic component”. A power resistor would provide a particularly good application as the heat dissipation would be high. The edge-printed track could be used to form a heater, for example in temperature-controlled applications. Use as an inductor would be particularly advantageous where a large area is needed, such as for a position sensor. Another potential application would be for use in a delay line. A track disposed on an edge surface could be used to perform numerous other functions.
It will be appreciated that, if both the back surface 44 and the mounting surface 34 have circuitry disposed thereon, it would not be necessary to provide a return path for the conductive track. Instead, the conductive track 40 would form a connection between the circuitry on the mounting surface 34 and the circuitry on the back surface 44.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0400363.8 | Jan 2004 | GB | national |
