GB2348320A

GB2348320A - A non-conductive intermediate frame for circuit boards

Info

Publication number: GB2348320A
Application number: GB9906364A
Authority: GB
Inventors: Marc Simon Anthony Norridge
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 1999-03-20
Filing date: 1999-03-20
Publication date: 2000-09-27
Anticipated expiration: 2019-03-20
Also published as: GB9906364D0; GB2348320B

Abstract

A non-conducting frame 1 for fitting between printed circuit boards is constructed as a single piece moulding. The frame 1 has a number of slots in the inner surfaces of its side walls and a number of screw bosses formed as part of the moulding. Identical dual spring connectors 10 are pressed into the slots 6 in the side walls to provide electrical connections to circuit boards fitted to the top and bottom of the frame. The dual spring connectors are symmetric about one major axis and therefore are accepted into a slot 6 in either one of two orientations. The screw bosses provide for clamping of the frame to the circuit boards.

Description

Intermediate frame for circuit boards This invention relates to an intermediate frame to space, separate and connect circuit boards and to provide a measure of shielding from electrical radiation for components enclosed by the frame.

The design of electronic units generally and mobile phones in particular is directed toward a reduction in the size and the number of components without compromising performance. The use of frames for fitting between printed circuit boards (PCB's) to provide the required spacing between the circuit boards whilst giving protection from electromagnetic interference is well established.

The shielding construction disclosed in US 5 271 056 to Pesola et al for example makes use of the ground foils of the circuit boards in combination with a conductive frame to which they are secured to provide shielding. In such constructions, difficulties are encountered with interconnection between the circuit boards separated by the frame. The earthed intermediate frame disclosed in US 5 253 146 to Halttunen et al provides solutions to some of the difficulties associated with the interconnections between circuit boards.

There remains a need for an intermediate frame of simple construction providing a measure of protection from radiated electrical interference whilst allowing circuit boards to be interconnected easily.

It is an object of the present invention to provide a combined spacer, RF shield and inter-board connector thereby reducing over the prior art the number of components and the costs of manufacture and assembly.

According to the invention there is provided an electrically non-conductive frame for fitting between circuit boards said frame comprising a single piece moulding with a plurality of slots in the inner surfaces of its side walls, said slots being substantially normal to the circuit boards fitted to the frame and accepting and retaining dual spring connectors with said connectors providing interconnections between circuit boards fitted to the frame.

An example of the invention will now be described with reference to the figures in which like reference numerals identify identical elements and wherein: figure 1 is a pictorial view of an intermediate frame, figure 2 is a plan view of an intermediate frame, figure 3 is a side elevation of an intermediate frame, figure 4 is a pictorial view of a spring connector, figure 5 is a pictorial view of part of the inner wall of the frame.

With reference to the figures, an intermediate frame 1 for circuit boards is illustrated. The intermediate frame 1 shown is generally rectangular with end walls 2 and 3 and side walls 4 and 5. The frame 1 is manufactured as a single piece moulding from a non-conducting plastic material e. g PC/ABS. Features of the moulding include the provision of a number of slots 6 within the inner walls 2a, 3a, 4a and 5a, screw bosses 7 and 8 with apertures 7a and 8a and an extension 9 to side walls 4 and 5. The purpose of the slots 6 is to accept into engagement the dual spring connectors 10 shown pictorially in figure 4.

The dual spring connectors 10 are formed as a single piece of metal of uniform thickness having a central part 11 for engagement with a slot and two outer spring members depending from said central part, bent toward the same axial direction and having arcuate contacts 14,15 at their distal ends. Dual spring connectors 10 are manufactured from an electrically conductive material with suitable properties for spring connectors e. g beryllium copper. The arcuate contacts 14,15 may be surface coated (flashed) with gold or rhodium. The dual spring connectors 10 are symmetrical about the axis Y-Y and so may be stitched more easily into any slot.

The extensions 9 to side walls 4 and 5 are for acceptance of a circuit board on the top of the frame. The screw bosses 7 and 8 and apertures 7a and 8a allow the frame to be clamped to upper and lower circuit boards so as to provide the correct spacing and good electrical contact.

The dual spring connectors 10 are stitched (pressed) into slots 6. The required connections between upper and lower circuit boards separated by frame 1 are provided by dual spring connectors 10. More dual spring connectors 10 are provided than are needed to satisfy the circuit interconnections between the upper and lower circuit boards fixed to the frame. The additional connectors 10 connect with the earth foils of the top and bottom circuit boards.

It is not necessary for all of the slots 6 to be occupied by a dual spring connector 10. Components within frame 1 are therefore largely shielded from interference by the upper and lower earth foils of the circuit boards between which the frame 1 is fixed. Additional shielding is provided by those connectors 10 whose upper and lower dual spring connectors are earthed to both the upper and lower foils.

It was found by experiment that a satisfactory level of protection from radiated interference was obtained when every fifth slot was occupied by a dual spring connector connected to the earth foils of the circuit boards fixed to the frame. The scale of the parts used in experiment provided for a dual spring connector connected to the earth foils of the circuit boards fixed to the frame at least every centimetre.

With reference to figure 5, which is a pictorial view of part of the inside wall of the frame, it can be seen that the lower parts of slots 6 are wider than the upper parts. During production of the frame, the dual spring connectors 10 can be pushed into the lower parts of the slots 6 until movement of the connectors 10 is arrested. When movement of the connectors 10 is arrested they are retained in engagement with the slot 6 by the resilience of the plastic from which the frame is made.

Problems could arise with use of frame 1 in respect of mutual interference between components or signal leads enclosed within or carried by the frame. It has been found, however, that such problems can be accommodated relatively easily in the design layout.

Claims

Claims 1. An electrically non-conductive frame for fitting between circuit boards said frame comprising a single piece moulding with a plurality of slots in the inner surfaces of its side walls, said slots being substantially normal to the circuit boards fitted to the frame and accepting and retaining dual spring connectors with said connectors providing interconnections between circuit boards fitted to the frame.
2. An electrically non-conductive frame as in claim 1 in which a number of the dual spring connectors are connected to the earth foils of the circuit boards fitted to the frame.
3. An electrically non-conductive frame as in claims 1 and 2 in which a dual spring connector in every fifth consecutive slot is connected to the earth foils of the circuit boards fitted to the frame.
4. An electrically non-conductive frame as in claims 1 to 3 in which the dual spring connectors are formed as a single piece of metal of uniform thickness having a central part for engagement with a slot and two outer spring members depending from said central part, bent toward the same axial direction and having arcuate contacts at their distal ends.
5. An electrically non-conductive frame as in any preceding claim in which each dual spring connector is symmetric about one of its major axes Y-Y.