Protective shield of emc-type

SWEDEN

M2) PATENT WRITING (13) C2 (id 507 255 (51) International class ⁶

H05K 9/00 (19) SE

<img file="SE507255C2_D0001.tif" />

<td> (45)</td><td>Patent granted</td><td> 1998-05-04</td>

<td> (41)</td><td>Application generally available</td><td> 1998-02-23</td>

<td> (22)</td><td>The patent application was filed</td><td> 1996-08-22</td>

<td> (24)</td><td>Löpdaq</td><td> 1996-08-22</td>

(62) National application number (86) International filing date (86) Filing date for European patent application (83) Microorganism deposit

PATENT AND REGISTRATION (21) Patent Application Number 9βθ3θ48-1

Application received as:

χΐ Swedish patent application completed international patent application with number

I — in converted European patent application LI with number (30) Priority information (73) (72)

INVENTOR INVENTOR

Telephone company LM Ericsson, Lars-Anders Olofsson, Järfälla SE Stockholm SE

126 25 Stockholm SE

Sven-Erik Björksell,

<td> (74)</td><td>AGENT</td><td colspan="2">Norin K</td><td></td>

<td> (54)</td><td>NAME</td><td colspan="2">Screen Protectors</td><td></td>

<td> (56)</td><td colspan="3">CALLED PUBLICATIONS:</td><td></td>

<td></td><td></td><td>US A 5</td><td> 354</td><td> 951</td>

<td></td><td></td><td>US A 5</td><td> 506</td><td> 374</td>

<td></td><td></td><td>US A 5</td><td> 053</td><td> 924</td>

<td> (57)</td><td>SUMMARY:</td><td></td><td></td><td></td>

(174-35R), US A 4,754,101 (174-35R), (174-35 GC), US A 5,150,282 (361-818), (361-818)

The present invention relates to a screen protector (1) of

EMC type for, for example, electrical components (40) on a circuit board (30). The shield (1) comprises a frame (10) with associated cover (20), said frame (10) at its end facing the circuit board (30) comprising a flange (12). The frame (10) is arranged to be attached to the circuit board (30) by gluing, welding or soldering. The frame (10) is intended to surround at least one component (40) so that electrical contact is formed between said circuit board (30) and said frame (10) and between said frame (10) and said cover (20).

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Patrons in the field of patents indicate international identification. INID code Root rod within Hammer specifies international document code.

-εη7 ο ccw / Ο

TECHNICAL FIELD

The present invention relates to a surface mounted screen protector for components on, for example, a circuit board.

BACKGROUND OF THE ART

Shielding of components on PCBs is becoming increasingly important, especially as the signal speed approaches the Gbit range. It is well known that the radiation from certain components at high frequencies can cause interference in communication such as telecommunications. This phenomenon is called RFI, radio interference. Otherwise, interfering circuits can be screened with closed boxes or so &lt;r&gt;

the sensitive components are screened with closed boxes to prevent interference.

GB 2 226 187 describes a miniature screen protector for electronic components arranged on a circuit board. The screen protector includes a number of contact springs and a cover. The contact springs are arranged around the component and in electrical contact with the circuit board. The contact springs are essentially unformed. The lid includes a flat surface with side walls on all edges so that the lid resembles an open box. The size of this box is adapted to the contact springs on the circuit board. The sides are intended to be pushed into the U-shaped contact springs to form a screen protector.

WO 95/28074 describes a contact spring that can be used to contact a screen protector to a circuit board. This contact spring has a different appearance compared to the above mentioned contact spring, which ensures that the contact between the cover and contact spring is ensured and that the shielding is increased.

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The problem with the above contact springs is that they are quite complicated to arrange around the component on the circuit board. Moreover, this solution is not entirely optimal in terms of both space requirements and degree of shielding.

DISCLOSURE OF THE INVENTION

On circuit boards where certain components produce a lot of electromagnetic radiation, the location of these components must be chosen with great care so that the radiation does not cause operational interference. For example, on a single-sided circuit board where both a transmitter and a receiver are located, the minimum size of the circuit board is limited to how close to each other the transmitter and receiver can be located without causing interference.

One problem that arises when different products are moving towards smaller dimensions is that the shielding between sensitive components must be increased.

Another problem is that known screen protectors take up too much space and are complicated and time-consuming to apply to the circuit board either because they have to be hole-mounted in the circuit board or because they have to be held at the soldering torque. The above mentioned problems usually require hand assembly.

IN

The present invention is intended to solve the above-mentioned problems by providing a surface mounted screen protector, so-called EMC protection, over sensitive or interfering components on a circuit board. The EMC protection is in its simplest embodiment a frame with associated covers arranged around at least one component of the circuit board. The frame is attached so that it is in electrical contact with the circuit board. The lid is adapted to shape and size according to

-ςη7 frame so as to obtain as shielding-efficient EMC protection as possible.

The frame which can take all sorts of different shapes, for example circular, triangular and rectangular and is optimized to its size to precisely surround the component or components to be screened. The frame which can be made of any electrically conductive material or a material coated with an electrically conductive material may at its end towards the circuit board include a flange. This flange can align the frame when it is attached to the circuit board by means of, for example, soldering, welding or gluing. A joint material placed at the intended location on the circuit board next to the component to be shielded and with a shape which corresponds to the contour of the frame, causes a not too misplaced frame to be moved to the correct position by the surface tension of the joint material. The lid comprising a flat surface with walls arranged on all edges is adapted to shape and size according to the frame so that the lid is either pushed out of the frame or placed inside it.

An advantage of the present invention is that the screen protector takes minimal space and that it does not leak radiation through the frame.

Another advantage of the present invention is that the fastening is simplified in that the frame is constituted by a unit which cannot roll over.

A further advantage of the present invention is that with its flange on the frame it can be self-adjusted to the correct position.

Yet another advantage of the present invention is that mounting on a conveyor belt is simplified and simpler pick and placer bots can be used.

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The invention will now be described in more detail with the aid of preferred embodiments and with reference to the accompanying drawings.

DESCRIPTION

Figure 1 is a perspective view of an embodiment of an EMC shield according to the invention arranged on a substrate.

Figure 2 shows a partial cross-section of the EMC protection in Figure 1.

Fig. 3 shows a partial cross-section of another embodiment of the EMC protection.

* E. ·

Fig. 4 shows a partial cross-section of another embodiment of the EMC protection.

Figure 5 shows a partial cross-section of yet another embodiment of the EMC shield.

PREFERRED EMBODIMENTS

Figure 1 shows an embodiment of an EMC type 1 screen protector according to the invention. The screen cover 1 is mounted in this figure on a substrate 30. The screen cover comprises a frame 10 and a cover 20. The frame 10 can be attached to the substrate 30 by means of gluing, welding or soldering. On the inside of the walls of the frame 10 there are a number of contact elements 11. These contact elements 11 are designed in this embodiment as tension forks. The outer dimensions of the lid 20 are adapted to the inner dimensions of the frame 10 as shown in Figure 2. As the lid 20 is inserted into the frame 10, the side walls 21 of the lid 20 are squeezed down between the walls of the frame 10 and the clamping forks. Within the frame 10, the component 40 is positioned or positioned to be shielded. Said tension forks may also be provided on the outside of the frame 10.

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The inner dimensions of the lid 20 are then adapted to shape and size according to the outer dimensions of the frame 10 so that the side walls 21 of the lid 20 are squeezed down between the clamping forks and the outside of the frame 10.

A variant of contacting the cover 20 with the frame 10 is that the outer dimensions of the frame 10 are precisely adapted to the inner dimensions of the cover 20 so that these details are mechanically held together and in electrical contact with each other by the cover 20 being threaded over the frame 10 and contacting it by pressing fit. Of course, it is also conceivable that the outer dimensions of the lid 20 are adapted to the inner dimensions of the frame 10 so that the lid 20 fits within the frame 10 so that

4r&gt;

said electrical contact and mechanical retention between these parts is again created by press fit, see Figure 3.

Instead of using tension forks or press fit to create electrical contact between the frame 10 and the cover 20, a number of other designs may be used. A variant could be that, just as before, the frame 10 is securely attached to the substrate 30. The lid 20 is sized to either fit inside the frame 10 or be threaded over the frame 10. If the cover 20 is intended to fit in the frame 10, a number of contact members in the form of grooves may be provided on the outside of the cover 20 of the cover 20 and corresponding grooves are provided on the inside of the frame 10. The flutes of the cap 20 and the flutes of the frame 10 are snap together to thereby create mechanical and electrical contact between the cap 20 and the frame 10, see Figure 5.

Yet another variant may be provided on the frame 10 a number of bulges 15 in the form of, for example, semi-spheres which are adapted to corresponding spheres on the side walls 21 of the lid 20. If a number of bulges 25 are provided on the side walls 21 of the lid 20, corresponding bulges 15 are provided.

507 255 on the frame 10. If a plurality of recesses 25 are provided on the side walls 21 of the cover 20, the corresponding recesses 15 are provided on the frame 10. The cover 20 can either be adapted to be threaded over the frame 10 or fit within it, the recesses or recesses 25 on the side walls. 21 will fit into corresponding protuberances or recesses 15 on the frame 10, see Figure 5. This embodiment plus the one with grooves is particularly suitable for small dimensions of the screen protector.

Yet another variant of contacting the cover 20 to the frame 10 is that the cover 20 is provided with a plurality of tabs 24 along the side wall 21. These tabs 24 are bent toward the center of the cover 20 when the cover 20 is to be pulled over the frame 10 and bent out from the center of the lid 20 when the lid 20 is to fit in the frame 10, see Figure 4. The tongues can also be bent at their free end towards the side wall 21.

On the frame 10 may be provided a flange 12 at the end which is to be connected to the circuit board. The flange 12 may be directed toward the center of the frame 10 as in Fig. 3 or out of the center of the frame 10 as in Fig. 4. The flange 12 allows the frame 10 to be self-adjusted to the correct position by the surface tension of the fastening material 50. If the frame 10 is misplaced relative to a solder material arranged on the circuit board 30, the frame 10 may move to the center of said solder material as it begins to melt.

In order to obtain the best shielding bandwidth as possible, the material in the EMC protection can be made of some electrically conductive material with magnetic properties.

The walls of the frame 10 may be slightly bent 12 at the bottom towards the substrate 30 to which the frame 10 is attached. The bending of the walls

-5 Ο 7 adjacent to the substrate can either face the frame 10 from the same.

The invention is, of course, not limited to the embodiments described and shown in the drawings, which are modified within the scope of the appended claims.

255 or out those above without can

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