MXPA01006866A - An electronic circuit board, an arrangement comprising an insulating material and an electronic circuit board - Google Patents

Abstract

An electronic circuit board (6) has a surface with at least one conducting island (7), and the surface is arranged proximate to a first insulating material (3) having a number of holes (8) which correspond to at least some of the conducting islands (7) and through which the conducting islands (7) may be reached. At an end thereof facing the surface, each hole (8) has an area which is larger than the area of the corresponding conducting island (7). A conducting area (10;14, 15, 16, 17) adapted to carry off an electrostatic discharge (ESD) is located on the surface proximate to the conducting islands (7) and within the area of the holes (8), and elements (9;19) of a second insulating material are provided in the holes (8). Thus the electronic circuit board can withstand electrostatic discharges without the circuitry of the board being damaged.

Description

A BOARD OF ELECTRONIC CIRCUIT, A PROVISION THAT UNDERSTANDS AN INSULATING MATERIAL AND A BOARD OF ELECTRONIC CIRCUIT The invention relates to an arrangement comprising a first insulating material and an electronic circuit board having a surface on which at least one insulating island is located, said surface being positioned next to the first insulating material, said first insulating material which has a number of orifices corresponding to at least some of the conductive islands and through which the conductive islands can be reached, each of said orifices having, at an end thereof which confronts said surface, an area that is greater than the area of the corresponding conductive island. Furthermore, the invention relates to an electronic circuit board thereof. Said circuit boards and arrangements are used for many purposes. An example is the electronic safety circuits for Ll-lón battery packs (Lithium-ion). Ll-lón batteries are sensitive to a number of factors, including overload. Therefore, all battery packs that include one or more Li cells require a circuit of electronic security components that can protect the Li cell against the critical levels of for example, charging voltage or charging current.

In the worst case the battery can explode if it is overloaded and therefore the electronic safety components are vital for the safety of the users of the battery pack, consequently, it is frequently required that the battery pack suppliers test the components electronic after the complete package has been assembled in a production line. This is commonly done by attaching probes to test points through holes in the plastic housing of the battery pack, however, those holes expose the sensitive parts of the electronic safety components that could be damaged by electrostatic discharge (ESD) after that the test has been carried out. Normally, the holes will be sealed after the battery pack has been tested on the production line, although this is often done by a label that can be easily damaged if it comes in contact with a sharp object such as a pencil or a ballpoint pen . Even with the best sealing methods cracks will always be present and therefore the risk of damage through ESD remains. If the electronic components that protect the Li cell are destroyed by a spark of ESD after the test, the result is a battery pack without functional safety electronic components and, as mentioned before, in the worst case this can cause an explosion or eruption of the battery cell due to, for example, overloading the Li cell.

Although this problem has been described in relation to the Li-ion battery packs, the same situation exists for many other applications in which the electronic circuit can be destroyed by ESD through the orifices in a surrounding housing. Therefore, it is an object of the invention to provide an arrangement of the aforementioned type that can resist electrostatic discharges without damaging the board circuits. According to the invention, this object is achieved since a conductive area adapted to bear an electrostatic discharge (ESD) is located on the surface near the conductive islands and within the area of the holes and that the elements made of a second insulating material are provided in said holes. When an insulating material is provided in the hole, an ESD spark will impact between this material and the surrounding material and strike the circuit board underneath. By placing a conductive area within the hole area so that it more or less surrounds the conductive island, the spark will hit this area instead of hitting the conductive island that is part of the sensitive circuit and therefore, the circuit will be protected. As set forth in claim 2, the arrangement may comprise electronic security components for a battery and the first insulating material may be part of a battery housing. As mentioned before, this is one of the typical applications of said circuit board. In addition, as set forth in claim 3, the conductive islands may conveniently be test points which are adapted to be used during the circuit board test procedure. As set forth in claim 4, the second insulating material may conveniently be an elastic material. This implies that the material will be sufficiently flexible to fill the entire orifice and therefore minimize the cracking between the two materials in which an electrostatic discharge can impact. In addition, the elements can be secured in the hole without the use of any adhesive, which also means that they can be easily removed again, allowing for either additional or repeated testing of the circuit at a later stage. According to one embodiment of the invention, which is set forth in claim 5, the conductive area adapted to support an electrostatic discharge has the shape of a circular ring located around each conductive island. In this way, the island is completely surrounded by the conductive area and therefore protected. According to an alternative embodiment of the invention, which is set forth in claim 6, the conductive area adapted to support an electrostatic discharge has the form of a number of discrete areas placed around each conductive island. This is a more flexible solution that still maintains an acceptable level of protection. In addition, it should be noted that the conductive area adapted to withstand electrostatic discharge may also have other shapes. According to a preferred embodiment of the invention, which is set forth in claim 7, the conductive area adapted to support an electrostatic discharge is connected to a ground plane. Often, a ground plane will be well suited to withstand electrostatic discharge, although depending on the voltages supplied the conductive area may also be connected to a positive or negative supply rail. As set forth in claim 8, the conductive area adapted to support an electrostatic discharge may have a thickness that is greater than the thickness of the conductive islands. This partially means that the upper part of the area is closer to the insulating materials, thus improving the probability that an ESD spark will impact this area instead of the island, and partially that the area is capable of withstanding a greater current in case of an impact. As set forth in claim 9, the probability that an ESD spark will impact the conductive area adapted to support an electrostatic discharge instead of the island can be further improved when this area is provided with raised or pointed means. This is due to the fact that electrostatic discharges are attracted to said high media.

As mentioned, the invention further relates to an electronic circuit board having a surface on which at least one conductive island is located, said surface adapted to be positioned proximate to a first insulating material having a number of holes that they correspond to at least some of the conductive islands and through which the conductive islands can be reached, each of the orifices that has, at one end thereof confronting the surface, an area that is greater than the area of the corresponding conducting island, wherein a conductive area adapted to support an electrostatic discharge (ESD) is located on said surface close to the conductive islands and within the area of the holes. By placing a conductive area within the area of the hole so that it more or less surrounds the conductive island, the spark will hit this area instead of hitting the conductive island which is part of the sensitive circuit, and therefore will protect the circuit. As stated in claim 11, the electronic circuit board may comprise electronic security components for a battery and the first insulating material may be part of a battery housing, as mentioned above, this is one of the typical applications of said circuit board. In addition, as set forth in claim 12, the conductive islands can conveniently be test points that are adapted to be used during a test procedure for the circuit board. According to one embodiment of the invention, which is set forth in claim 13, the conductive area adapted to support the electrostatic discharge has the shape of a circular ring located around each conductive island. In this way, the island is completely surrounded by the conductive area and is therefore well protected. According to an alternative embodiment of the invention, which is set forth in claim 14, the conductive area adapted to support the electrostatic discharge has the form of a number of discrete areas placed around each conductive island. This is a more flexible solution that still maintains an acceptable level of protection. In addition, it should be noted that the conductive area adapted to withstand electrostatic discharge may also have other shapes. According to a preferred embodiment of the invention, which is set forth in claim 15, the conductive area adapted to support an electrostatic discharge is connected to a ground plane. Often a ground plane will be well suited to withstand an electrostatic discharge, but depending on the supply voltages the conductive area may also be connected to a positive or negative supply rail. As set forth in claim 16, the conductive area adapted to support an electrostatic discharge may have a thickness that is greater than the thickness of the conductive islands. This partially means that the upper part of the area is closer to the insulating materials, thus improving the probability that an ESD spark will impact this area instead of the island, and partially that the area is capable of withstanding a greater current in case of an impact. As set forth in claim 17, the probability that an ESD spark impacts the conductive area adapted to support an electrostatic discharge instead of the island can be further improved when this area is provided with raised or pointed means. This is due to the fact that electrostatic discharges are attracted to said high media. The invention will now be described more fully with reference to the drawing, in which Figure 1 is a battery pack in which the invention can be used, Figure 2 shows a first embodiment of the invention in section viewFigure 3 shows a printed circuit board of the embodiment of Figure 2 from above, Figure 4 shows an alternative embodiment with separate conductor areas, Figure 5 shows an improvement of the embodiment of Figure 2, and Figure 6 shows an alternative embodiment of a plug for use in the invention. Figure 1 shows a battery pack in which a Li-ion battery 2 is enclosed in a plastic housing 3. The poles of the battery are connected via cables 4, 5 to a printed circuit board 6 containing a electronic safety circuit adapted to protect the battery 2 against overload in the form of for example, a high voltage or a high voltage current. Frequently the electronic components are required to be tested after assembly of the complete battery pack. Therefore, the test points in the form of conductive islands 7 are provided on the printed circuit board 6. For reasons of clarity only one conductive island 7 has been shown, although there will usually be a number of test points. Each test point 7 can be accessed by a probe through a hole 8 in the plastic housing 3 when the test procedure is carried out. Due to the holes 8, the test points 7 and thus the electronic safety circuit on the printed circuit board 6 are exposed to electrostatic discharges (ESD) which can destroy the circuit. If such a situation occurs, battery 2 is no longer protected against overcharging and the result may be an explosion or battery explosion. Figures 2 and 3 show how this problem can be solved. It is noted that the test point 7 on the printed circuit board 6 is placed below the hole 8 in the plastic housing 3. A plug 9 made of an insulating material such as rubber has been inserted into the hole 8. Although the plug 9 fills the hole 8 completely, small cracks 11 will be left between the plug 9 and the edge of the hole 8. A conductive area 10 in the shape of a circular ring is placed on the printed circuit board 6 below the edge line between the plug 9 and the plastic housing 3. If an electrostatic discharge hits through the crack 11, it will impact the conductive area 10 instead of the test point 7. As shown in figure 3, the conductive area 10 is connected to the through the conductor 12 to a ground plane 13, and an ESD hitting the area 10 will then pass through the ground plane 13 without altering the test point 7. Although the hole 8, and therefore the plug 9, will often have In a circular cross section, it should be noted that other shapes are also possible. Similarly, the ring 10 may even have other shapes than the circular shown in figure 3. It will commonly be adapted to the shape of the hole 8. It should be noted that a supply rail can also be used instead of the ground plane 13. positive or negative depending on the polarity and voltage of the battery 2. As will be seen from Fig. 2 the plug 9 extends above the level of the surface of the plastic housing 3. This has an additional positive effect. When the battery pack is placed in a device, such as a mobile phone, the rubber plugs extending over the plastic surface will support the battery pack mechanically against the device so that it is less sensitive for example to vibrations. Another advantage of using a flexible plug 9, for example of rubber, is that the plug can be removed and the circuit tested later at a later stage, if necessary. Although the modality shown in mode 3 is a preferred embodiment, other distributions are possible. In Figure 4 an example is shown in which the circular ring 10 is replaced by a number of discrete areas 14, 15, 16 and 17. Although not shown, each of these areas must be connected to, for example, the ground plane. Those connections do not need to be placed on the same board surface. They can be placed in the intermediate layers or on the opposite surface. As can be seen in Figure 2, the conductive area 10 is made of a metal layer that is thicker than the layer of the test point 7 in this embodiment. This improves the probability that an ESD hits the area 10 instead of the test point 7. This probability can be further improved, as shown in Figure 5. Here a raised member 18 is placed in the conductive area 10 and the edge of the plug 9 is adapted therein. The raised member 18 can have different shapes such as for example separate pins or a circular ridge on the conductive area 10. Fig. 6 shows a further embodiment. Here a different form of the hole is used in the plastic housing 3 and accordingly a plug 19 is adapted. One advantage of this mode is that the plug is better fixed in the hole and the cracks 11 will be smaller, thus improving the protection . In addition, an impact of an ESD, when it hits the conductive area 10, will have a direction away from the island or test point 7. Although a preferred embodiment of the present invention has been shown and described, it is not restricted to the present invention. same, but may also be presented in other forms within the scope of the subject matter defined in the following claims.

Claims (10)

1. An arrangement comprising a first insulating material and an electronic circuit board having a surface on which at least one conductive island is located, said surface being placed proximate to the first insulating material, the first insulating material having a number of orifices that correspond to at least some of the conductive islands and through which the conductive islands can be reached, each of the holes that have, at one end of them that confronts said surface, an area that is larger than the area corresponding to the conductive island, characterized in that a conductive area adapted to support an electrostatic discharge is located on said surface close to the conductive islands and within the area of the holes, and that the elements made of a second insulating material are provided in said holes.

2. An arrangement according to claim 1, characterized in that it comprises electronic security components for a battery and that said first insulating material is part of a battery housing.

3. An arrangement according to claim 1 or 2, characterized in that the conductive islands are test points.

4. An arrangement according to claims 1-3, characterized in that the second insulating material is an elastic material.

5. An arrangement according to claims 1-4, characterized in that the conductive area adapted to support an electrostatic discharge has the form of a circular ring located around each conductive island.

6. An arrangement according to claims 1-4, characterized in that the conductive area adapted to support an electrostatic discharge has the form of a number of discrete areas placed around each conductive island.

7. An arrangement according to claims 1-6, characterized in that the conductive area adapted to support an electrostatic discharge is connected to a ground plane.

8. An arrangement according to claims 1-4, characterized in that the conductive area adapted to support an electrostatic discharge has a thickness that is greater than the thickness of the conductive islands.

9. An arrangement according to claims 1-4, characterized in that the conductive area adapted to support an electrostatic discharge is provided with high means.

10. An electronic circuit board having a surface on which at least one conductive island is located, said surface adapted to be positioned next to a first insulating material having a number of holes corresponding to at least some of the conductive islands and through which the conductive islands can be reached, each of the holes that has, at one end thereof confronting said surface, an area that is greater than the area of the corresponding conductive island, characterized wherein a conductive area adapted to support an electrostatic discharge is located on said surface near the conductive islands and within the area of the holes. eleven . An electronic circuit board according to claim 10, characterized in that it comprises electronic security components for a battery. 12. An electronic circuit board according to claim 10 or 11, characterized in that the conductive islands are test points. 13. An electronic circuit board according to claims 10-12, characterized in that the conductive area adapted to support an electrostatic discharge has the shape of a circular ring located around each conductive island. 14. An electronic circuit board according to claims 10-12, characterized in that the conductive area adapted to support an electrostatic discharge has the form of a number of discrete areas placed around each conductive island. 15. An electronic circuit board in accordance with claims 10-14, characterized in that the conductive area adapted to support an electrostatic discharge is connected to a ground plane. 16. An electronic circuit board according to claims 10-12, characterized in that the conductive area adapted to support an electrostatic discharge has a thickness that is greater than the thickness of the conductive islands. 17. An electronic circuit board according to claims 10-12, characterized in that the conductive area adapted to support an electrostatic discharge is provided with high means.