WO2011114104A1

WO2011114104A1 - Improved carrier for electronic components

Info

Publication number: WO2011114104A1
Application number: PCT/GB2011/000376
Authority: WO
Inventors: Stephen Thomas Hopwood; David Beckett
Original assignee: Syfer Technology Limited
Priority date: 2010-03-17
Filing date: 2011-03-17
Publication date: 2011-09-22
Also published as: GB201004467D0

Abstract

The application discloses an electronic-component carrier (10) to mount a component to a surface. The carrier (10) comprises a generally tubular casing (11); the casing (11) including, around its inner surface a ridge (25) on which a component rests and is positioned. One or more resilient electronically conducting contacts is/are included (12) at least a portion of the or each contact (12) extending inwardly into the casing to engage a component and enable a component to be connected to a circuit, via one or more securing means (13). The or each securing means enables the carrier to be secured to a PCB or the like and thereby be incorporated into a circuit.

Description

IMPROVED CARRIER FOR ELECTRONIC COMPONENTS

Field of the Invention

The present invention relates to a means of retaining and carrying electronic components. The means also enables different individual components to be held in close proximity to one another.

Background to the Invention

In many electronic applications certain basic individual circuit elements are configured together into a more complex circuit and used in that configuration so frequently that the configuration can be obtained industrially in an already assembled form. In this way costs of manufacture and raw materials can be significantly reduced. As exemplified herein, Pi filters, X2Y™ capacitors number amongst these. It will be recognised by the skilled person however that the invention described in the present application, to assemble multi-element components, is more widely applicable without further inventive input.

With respect to surface mounted Pi filters which are known in the prior art, the following may be noted. Broadly, those known have limitations in the available capacitance value (low frequency performance), compatibility with lead-free soldering techniques - due to temperature limitations - and mechanical strength in that they are susceptible to damage. For example, three assembly methods may be cited to illustrate the problems. Firstly, the capacitance of tubular capacitors is a factor of the wall thickness and of the length of the tubes. Inductance is provided through ferrite bead inductors over the pin inside the tube. Such capacitors have low maximum capacitance (typically around 20nF). Moreover, the thin walls of the tube are prone to cracking.

Secondly, so called discoidal capacitor based filters require two discoidal capacitors to make a single Pi filter. Inductance is provided from a ferrite bead inductor on a through pin which passes between the two discs. Although high capacitance can be achieved, construction is complex and there are issues with mechanical stress.

Thirdly, chip capacitor based filters provide high capacitance and can also be easily assembled into a robust article. Nevertheless, chip capacitor based filters cannot readily be used with lead-free solders as there is a danger of internal solder joints re-flowing. Moreover, mechanical stress problems can develop on circuit boards, relating to board handling and design, for example as the area of the board increases.

The present invention seeks to address the above problems and provide a means of retaining individual elements together to yield more complex functionality and also enable the assembled article to be secured in position. The component carrier disclosed is also sufficiently durable and robust to be included in harsh environments, for example the vibration and heat associated with automotive applications.

Summary of the Invention

According to the invention there is provided an electronic-component carrier to mount a component to a surface, the carrier comprising a generally tubular casing;

the casing including, around its inner surface a ridge on which a component rests and is positioned;

one or more resilient electronically conducting contacts at least a portion of said contact extending inwardly into the casing to engage a component and enable a component to be connected to a circuit, via one or more securing means, whereby the or each securing means enables the carrier to be secured to a PCB or the like and thereby incorporated into a circuit.

Optionally, the casing has a quadrilateral cross-section such as a rectangular or square shape which enables devices to be arrayed in close configuration to one another. Optionally, a conducting contact comprises a metal strip which is secured to the inner surface of the carrier by a push-fit connection to ease manufacture. Further optionally, at least a portion of the or each resilient contact is encased within the wall of the tubular casing to give a secure attachment.

Optionally the or each securing means comprises a solder ensuring that an electronically conducting contact can be made by conventional means.

Preferably, the carrier comprises two or more ridges enabling more components to be contained within the same carrier, thus allowing more complex circuits to be devised.

Preferably the or each conducting contact includes two or more inwardly extending portions which again increases the flexibility of the circuit produced by the components: particularly where a carrier includes two or more components. Moreover the inward, extending portions can also cushion the components against mechanical and thermal stresses.

The carrier material is optionally selected from a plastics material, said plastics material having a high performance and able to withstand relatively high temperatures, for example a polyamide or the like.

Brief Description of the Drawings

The invention is now described with reference to the accompanying drawings which show by way of example only, seven embodiments of a carrier. In the drawings;

Figures 1 a-d are respectively, a plan, front, side and underside, view of a first embodiment of a carrier;

Figures 2a,b-6a,b are front and side sections through second to sixth embodiments of a carrier; -^{' "} Figures 7a, b are enlarged views of a seventh embodiment of a carrier;

Figures 8a,b are views of the embodiment of ^' Figure 7 including a Pi filter component;

Figure 9 illustrates a circuit equivalent to the assembly shown in Figures 8a, 8b; Figures 10a, 10b are further views of the embodiment of Figure 4 including an X2Y™ capacitor component;

Figure. 1 1 illustrates a circuit to which the assembly shown in Figures 10a, 10b is equivalent;

Figure 12 illustrates a use of the assembly of Figures 10a, 10b; and

Figures 13a, 13b are views of an eighth embodiment of a carrier.

Detailed Description of the Invention

The invention as described herein describes a more robust means of attaching an electronic component to a printed circuit board (PCB) or other surface. In addition, the invention also allows multiple components to be pre-assembled into one unit comprising a more complex circuit, which assembled circuit can then be mounted to the PCB in a single step.

In its broadest aspect, a carrier according to the invention has a casing which is substantially tubular, the casing including a narrowing or closure on its inner surface to retain in position an electronic component. The narrowing or closure can extend, when required across the inner surface of the casing: provided that sufficient space is left for passage of the electrical contacts described below. Electrical contact with a surface to which the carrier is attached is maintained by sprung contacts secured to the inner wall of the casing. To provide additional means of retaining the component, spring clips extending from the casing, hold the component in position. Each casing can be formed such that the contents are sealed within in order to increase environmental protection.

Referring now to Figures la-d, these illustrate the basic form of a carrier, generally referenced 10. The carrier 10 comprises a tubular casing 11 of rectangular cross-section. The casing 1 1 is typicall formed from a rigid plastics material such as a polyamide. The plastics material is of high performance and ideally capable of withstanding high temperatures such as those involved in soldering a carrier to a PCB - typically around 270C.

Arrayed on the inside walls are electrically conducting contacts 12. The contacts 12 are spring loaded which enables them firstly to be secured into the casing 1 1 by means of a push-fit type connection. This can be achieved for example by pushing the contact over a small protrusion (not illustrated) in the side wall of the carrier 1 1, which then acts to retain the contact 12. Secondly, the resilient nature of the contacts 12 means that any stress forces on the carrier, generated on installation of the carrier into position or under use conditions are taken up by the contacts 12. It is to be further noted that the contacts 12 are, within the carrier, electrically isolated from each other.

At the foot of each contact 12 is a solder pad 13 which enables electrical contact with the PCB to be realised and for the components held within the carrier 10 to be incorporated into the circuit of the PCB.

Extending from one or more contacts 12 are compliant contacts 14 which establish electrical connection between the electronic component and the contact 12. In addition, the compliant contacts 14 act to provide a further cushioning effect against mechanical forces and stresses acting on the carrier 10. The compliant contacts 14 can be made for example of a beryllium/copper alloy, steel or other suitable material known in the art.

A further feature, see Figures 2a, 2b of the carrier 10 is that of the ridge 25 which extends inwardly from the carrier wall and supports and positions an electronic component. The ridge 25 is formed of a non-compliant material to provide a robust support. Moreover, because the ridge does not grip a component to hold the component in position but merely supports the component, a single ridge is able to be used for different sizes of component resulting in a reduction of manufacturing costs. Incorporation of the above features enables different carriers to have different properties and enables a single unit to be produced containing a complex circuit, the properties of which circuit depend on the individual components and the connectivity displayed. In this respect, examples of different carriers are shown in Figures 2-6.

In Figures 2a, 2b a carrier 20 has a ridge 25 approximately halfway up the internal wall 21. The ridge 25 divides the carrier 20 into two compartments or cavities each capable of holding a component. The carrier 20 has four contacts 22, each having a solder pad 23 if required. Moreover, a compliant contact 24 extends from each contact 22 to engage a component retained in the upper cavity of the carrier 20 and so provide support and connections to a PCB or other article.

Figures 3a, 3b show a carrier 30 having a ridge 35 at the base of the carrier 30, and only therefore a single cavity to hold a component (for example providing connection to an X2Y™ capacitor for a harsh application environment).

Figures 4a, 4b show again a two-compartment carrier 40 in which compliant contacts 44 are provided for a component in both compartments, to enable the two components to be electrically connected both to each other and to the PCB.

Figures 5a, 5b show a carrier 50 having the same connectivity as for the carrier 20 in Figure 2. The compliant contacts 54 are however moulded into the walls 51 of the carrier 50.

Figures 6a, 6b show carriers 60a, 60b which are so configured to enable, for example, multiple multi-layer chip capacitors (MLCC) to be stacked together in close proximity, add stress relief to the assembly and occupy a relatively small board area.

Figures 7a, 7b show a carrier 70 in which the connectivity is again different from previously illustrated, in that the component in the upper cavity is served by four compliant contacts 74, but that i the lower cavity by only two compliant contacts 74. This again illustrates the flexibility of connectivity which can be achieved.¹ Figures 8a, 8b illustrate the use of the carrier 70 of Figures 7a, 7b to produce a surface mountable Pi configuration electromagnetic interference (EMI) low pass filter. A carrier 70 supports, within the upper cavity a multi-layer chip capacitor 71. The four compliant contacts 74a-d in the upper cavity provide both signal and earth contacts, to the MLCC. A surface mounted ferrite induction block 76 including a conductor 77 which passes through the block 76 is fitted in the lower cavity. As can be seen from the contacts 74a-d, the MLCC 71 is connected to ground through the compliant contacts 74b₃ c and to the induction block conductor 77 through the compliant contact 74a, d and the contacts 72a, 72b. Solder pads 75 enable the carrier and components to be soldered to a PCB or similar contact. It should be noted that the solder pads can be coextensive with the contacts 72a, 72b and be formed of the same material as said contacts to give additional mechanical strength.

By use of the above assembly a circuit as shown in Figure 9 is produced which is a well-known configuration used for low pass filtering wherein high frequency electrical noise is shunted to ground through two capacitors, whilst being blocked by the inductor. Low frequency/DC signals pass unattenuated through the filter.

Figures 10a, 10b illustrate a combination X2Y™ capacitor filter assembly based upon the carrier shown in Figures 4a, 4b. The assembly shown has two MLCCs 100a, b which are connected together and to the transmission line through the compliant contacts 101, 102 and together and to ground through the compliant contacts 101b, 102b. All of the compliant contacts 101, 102, 101b & 102b are formed into surface-mounted solderable solder pads 103. The final assembly is sealed for environmental protection. A circuit, equivalent to the filter shown in Figure 10, is shown in Figure 11. Such filters have been shown to provide high filtering performance in electric motors. Typically the two X2Y™ chip capacitors 100a, 100b are of different values such th t the resonant peaks of the two occur at different frequencies and therefore have a cancelling effect. An example of the application of the carrier within an electric motor, the carrier . being used as a wide band filter to reduce emitted electronic noise from the motor is shown in Figure 12. In the motor, the chip 120 is located between line inputs to the motor. The chip 120 is best positioned in or adjacent to the motor housing for best performance.

Figures 13a, 13b illustrate a carrier 130 having similar connectivity to the carrier of Figures 7 and 8. The solder pads 131 in this embodiment are curved into a U- shape to retain the internal wall 132. This provides an advantage in that the solder pad 131 is provided with a positive means of being located. In addition the pad 131 is thereby made mechanically stronger as a possible stress area is removed. The result of this is that resulting solderable pad area is better for subsequent use such as assembly onto a board. The curved solder pad 131 can also be more easily inspected visually after the part has been assembled onto a PCB.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention.

Claims

1. An electronic-component carrier (10) to mount a component to a surface, the carrier (10) comprising a generally tubular casing (1 1);

the casing (1 1) including, around its inner surface a ridge (25) on which a component rests and is positioned;

one or more resilient electronically conducting contacts (12) at least a portion of the or each contact (12) extending inwardly into the casing to engage a component and enable a component to be connected to a circuit, via one or more securing means (13),

whereby the or each securing means enables the carrier to be secured to a PCB or the like and thereby incorporated into a circuit.

2. A carrier according to Claim 1, wherein the casing has a quadrilateral cross-section such as a rectangular or square shape.

3. A carrier according to any preceding claim, wherein a conducting contact comprises a metal strip which is secured to the inner surface of the carrier by a push-fit connection.

4. A carrier according to Claim 3, wherein at least a portion of the or each resilient contact is encased within the wall of the tubular casing to give a secure attachment.

5. A carrier according to any preceding claim, wherein the or each securing means comprises a solder ensuring that an electronically conducting contact can be made by conventional means.

6. According to any preceding claim, wherein the carrier comprises two or more ridges enabling more components to be contained within the same carrier.

A carrier according to any preceding claim, wherein the or each conducting contact includes two or more inwardly extending portions.

A carrier according to any preceding claim, wherein the carrier materia! is selected from a plastics material, said plastics material having a high performance and able to withstand relatively high temperatures.

A carrier according to Claim 8, wherein the plastic is a polyamide.

10. A carrier substantially as herein described with reference to and as illustrated by the accompanying drawing.