GB2337863A

GB2337863A - Method and means of forming a desired coil configuration

Info

Publication number: GB2337863A
Application number: GB9910593A
Authority: GB
Inventors: Frederick E Bott
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-05-09
Filing date: 1999-05-10
Publication date: 1999-12-01
Anticipated expiration: 2019-05-10
Also published as: GB9910593D0; GB2337863B

Abstract

A method or means of forming a coil arrangement comprises at least one substrate 1 including a conductive element 3 in which the substrate is arranged such that a plurality of said substrates may be stacked so that their conductive elements 3 form a desired coil configuration. The substrate 1 may be a multi-layered printed circuit board including printed conductive coil portions 3a, 3b. The substrate 1 may include radially projecting limbs 11, 12 which include conductive contact pads 2a, 2b, 4a, 4b. The contact pads are arranged such that they abut to form interconnections when a plurality of said substrates are stacked. Certain contact pads 2a, 2b may be connected to the coil 3 whilst others 4a, 4b provide at least one by-pass connection. The said projecting substrate limbs 11, 12 may include plated through holes 6, 7, 13, 14 which may be interconnected by wires such that certain coil portions in a stack of said substrates are interconnected to provide a desired coil configuration. The substrate may include a central opening 15 for receiving a magnetic core member.

Description

2337863 1 COIL SUBSTRATE This invention relates to coils used in chokes

and transformers.

According to a first aspect of the invention we provide a substrate comprising a length of coil winding, and the substrate being so arranged that, in use, a plurality of said substrates may be stacked so as to form a desired coil configuration.

Preferably the substrate comprises contact means, said contact means being arranged to at least partially provide electrical connection between at least two substrates in a stack of such substrates.

Most preferably the contact means at least partially provides electrical connection between adjacent substrates in a stack of such substrates.

Preferably the contact means comprises at least one electrically conductive feature provided on one side of the substrate.

Preferably at least one electrically conductive feature is provided on each side of the substrate.

Preferably at least one electrically conductive feature on one side of the substrate is electrically connected to at least one electrically conductive feature on the opposite side of the substrate.

Preferably at least one electrically conductive feature on one side of the substrate is connected to at least one electrically conductive feature on the opposite side of the substrate by a length of coil winding.

2 Preferably the contact means is disposed so as to register with contact means disposed on a facing side of an adjacent substrate in a stack of such substrates.

Preferably the at least one electrically conductive feature comprises an electrically conductive pad.

Preferably the contact means is formed at least in part by the process of screen-printing.

Preferably the length of coil winding is formed at least in part by the process of screen-printing.

Preferably the substrate is provided with an aperture which is suitably dimensioned so as to accommodate a magnetic core component.

Preferably the substrate is provided as a piece of printed circuit board.

Most preferably the substrate comprises multi-layer printed circuit board.

According to a second aspect of the invention we provide the method of 15 stacking substrates so as to achieve a desired coil configuration, wherein the substrates comprise a length of coil winding.

Preferably the substrates are stacked so that alternate substrates correspond to respective coils in at least part of the coil configuration.

Alternatively, the substrates may be stacked so that adjacent substrates correspond to a respective coil in at least part of the coil configuration.

3 The substrates may be stacked so that alternate substrates correspond to respective sides of a magnetic core in at least part of the coil configuration.

The invention according to a third aspect comprises a stack of substrates, 5 each substrate being in accordance with the first aspect of the invention.

The invention according to a fourth aspect is a coil configuration comprising a stack of substrates, the substrates each comprising a length of coil winding.

The invention will now be more particularly described, by way of 10 example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a substrate according to the first aspect of the invention, Figure 2 is a plan view of the substrate shown in Figure 1, Figure 3 is an exploded view of a transformer comprising substrates as shown in Figures 1 and 2, Figure 4 is a first perspective view of the transformer shown in Figure 3, Figure 5 is a second perspective view of the transformer shown in Figure 3, Figure 6 shows a front elevation of a second transformer configuration comprising substrates as shown in Figures 1 and 2, 4 Figure 7 shows a first side view of the transformer configuration shown in Figure 6, Figure 8 shows a second side view of the transformer configuration shown in Figure 6, Figure 9 is a front elevation of a choke configuration comprising substrates as shown in Figures 1 and 2, Figure 10 is a side elevation of the choke configuration shown in Figure 9 Figure 11 shows a perspective view of a second type of substrate, Figure 12 shows a plan view of the substrate shown in Figure 11, Figure 13 shows an underside view of the substrate shown in Figure 11, Figure 14 shows schematically an end view of the second type of substrate, Figure 15 shows schematically a view of the opposite end of the second type of substrate, and Figure 16 is a composite figure showing schematically end views of a stack of the second type of substrate and the corresponding circuit diagram of the resulting coil configuration.

Figures 1 and 2 show one embodiment of a substrate 1 according to the invention. The substrate 1 comprises contact means and a length of coil winding.

The length of coil winding 10 comprises two coil turns. However, the substrate 1 could of course be provided with more turns if desired.

The substrate 1 is formed from multi-layer printed circuit board which comprises a number of superimposed dielectric laminates which are bonded together. Such dielectric laminates are typically manufactured from epoxy resin with woven glass cloth reinforcement. Printed features on different layers are electrically connected by means of plated- throughholes. Individual laminates are not shown in Figure 1 for reasons of clarity.

The substrate 1 defines two limbs 11 and 12. The limb 11 has formed therein two plated-through-holes 13 and 14. The limb 11 also comprises contact means in the form of two electrically conductive pads 2a and 2b, and are formed by the process of screen-printing. The pads 2a and 2b are provided on opposite sides of the substrate 1. The pad 2a is connected to the plated-through-hole 13 and the plated-through-hole 13 is connected to one end of the length of coil winding 10. Similarly the pad 2b is connected to the plated-through-hole 14, the plated -through -hole 14 being connected to the other end of the length of coil winding 10.

The length of coil winding 10 comprises two coil sections 3a and 3b.

Each coil section 3a, 3b is formed by screen-printing tracking on respective outer surfaces of one of the dielectric laminates. The two coil sections 3a and 3b are connected in series by plated -through-hole 8.

Turning now to limb 12, the contact means comprises electrically conductive by-pass pads 4a and 4b. The pads 4a and 4b are provided on opposite sides of the substrate 1 and are interconnected via the platedthrough-hole 5 to provide by-pass means. The limb 12 has also formed 6 therein two apertures 6 and 7.Pads 4a and 4b are positioned diametrically opposite to pads 2a and 2b.

The substrate 1 is provided with a suitably sized central aperture 15.

Manufacture of the substrate 1 can be carried out as for conventional 5 printed circuit board manufacture.

As will become apparent, the use of such substrates allows for the assembly of chokes and transformers of a desired configuration.

The use of the substrates in assembling a transformer configuration will first be discussed.

Figure 3 is an exploded view of a transformer 16 comprising housing sections 17 and 18, coil component substrates la, lb, lc, ld, le, lf and lg, and insulated cables 19, 20, 21 and 22 (not shown in Figure 3).

Each housing section 17, 18 comprises a respective core section 23 and 24. The diameter of each core section 23, 24 substantially corresponds to that of the central aperture 15 of each substrate 1.

As can be seen from Figure 3, the substrates la to lg are stacked so that the pads 2a and 4a on a first substrate are in register with the pads 4b and 2b, respectively, on an adjacent substrate and effect connections therewith. The result is that alternate substrates correspond to the same coil thanks to the pads 4a and 4b which provide direct connection between the coil windings 10 of alternate substrates.

Turning to Figure 4, it can be seen that an exposed end 26 of the insulated cable 19 is in register with the plated- through-hole 13 of the 7 substrate lf and that an exposed end 27 of the insulated cable 20 is in register with the plated -through -hole 14 of the substrate 1 b. Conveniently the plated-through -hole 13 of the substrates 1d and lf serve as guiding means as the cable 20 is inserted.

Thus the coil windings of the substrates lb, ld and lf are now connected together via the pads 4a and 4b of the substrates le and lc. The coil windings 10 of the substrates lb, 1d and lf form a first transformer coil.

Turning now to Figure 5 it can be seen that an exposed end 28 of insulated cable 21 is in register with the plated-through-hole 13 of the substrate la and that an exposed end 29 of insulated cable 22 is in register with the plated-through-hole 14 of the substrate lg. The coil windings 10 of the substrates le and lc are interconnected via the pads 4a and 4b of the substrate ld. Thus the coil windings 10 of the substrates lc and le form a second transformer coil.

The insulated cables 19 and 20, 21 and 22 allow for the first and second transformer coils respectively to be connected to external circuits. Thus the transformer shown in Figures 3, 4 and 5 has a winding ratio of 3:2.

Electrical and mechanical connection is made by dipping each set of limbs in a solder-pot so that solder will flow up to cover the full areas 20 between each pair of facing pads, and to connect the exposed wire ends 26, 27 to the adjacent plated -through -holes.

It should be appreciated that various winding ratios can be obtained by connecting one or all of the cables 19, 20, 21 and 22 to different platedthrough-holes in the stack of substrates as required.

8 Figures 6, 7 and 8 show another example of a possible transformer configuration. More specifically the configuration is that of two centretapped isolated coils and comprises eight substrates, la', lbl, lc', ld', le', lfI, lgI, lh', two housing sections 171 and 18', and six insulated cables 30, 31, 32, 33, 34, 35. Each housing section 171 and 181 comprises a core section (not shown). Superimposed on Figure 6 is a schematic representation of the configuration with connection points thereon. The substrates are stacked as follows.

The pad 2b of the substrate la' faces the pad 4a of the substrate W.

The pad 4b of the substrate lbl faces the pad 2a of the substrate lc'.

The pad 2b of the substrate lc' faces the pad 4b of the substrate ld'.

The pad 4a of the substrate ld' faces the pad 2b of the substrate le' The pad 2a of the substrate le' faces the pad 4a of the substrate I.P.

The pad 4b of the substrate 1P faces the pad 2a of the substrate lgl.

The pad 2b of the substrate lg' faces the pad 4a of the substrate lhI.

Thus one isolated coil is formed from substrates lal, lcl, le', and lgI, and another isolated coil is formed from the substrates lbl, ld', lfI, lhI.

As can be seen from Figure 7, the cable 30 will be connected to the plated -through -hole 13 in the substrate lal, the cable 31 will be connected to the plated-through-hole 14 of the substrate lgI, and the cable 32 will be connected to the plated-through- hole 14 of the substrate le', which correspond to connection points Pl, P3 and P2 respectively.

As can be seen from Figure 8, the cable 33 is connected to the platedthrough-hole 13 in the substrate lbl, the cable 34 will be connected to the plated-through-hole 13 of the substrate ld' and the cable 35 will be 9 connected to the plated-through-hole 14 of the substrate lhI, which correspond to connection points S1, S2 and S3 respectively.

One application of the configuration shown in Figures 6, 7 and 8 is a push-pull converter.

Figure 9 shows one example of a possible choke configuration. Specifically it is a single continuous winding with two offset taps. The configuration again comprises eight substrates lal, lbl, W, ld', le', 1P, lgl and lhl, two housing sections 171 and 18', and four insulated cables 36, 37, 38 and 39. The substrates are stacked so that the pads 2a of adjacent substrates face each other and that the pads 2b of adjacent substrates face each other.

Thus a single continuous coil is obtained.

The cable 37 will be connected to the plated-through -hole 13 in the substrate lal and corresponds to connection point Pl. The cable 38 will be connected to the pl ated-through -hole 13 in the substrate 1h, and corresponds to connection point P4. The two taps are provided by the cables 36 and 39. The cable 36 will be connected to the platedthroughhole 14 of the substrate lal and corresponds to connection point P2. The cable 39 will be connected to the plated -through-hole 14 of the substrate 1P and corresponds to connection point P3.

It should be appreciated that if pads 4a and 4b and plated though-hole 5 were to be omitted then the resulting substrate could still be usefully employed. Use of such modified substrates requires that the pads 2a and 2b of adjacent substrates corresponding to different respective coils (for example primary and secondary coils) are not allowed to come into contact.

Figure 11 shows a second embodiment of the invention. Substrate 40, like substrate 1, is formed from multiple-layer printed circuit board. The substrate 40 comprises a length of coil winding 41 and is provided with twelve pads on each side of the substrate. As will be seen, pads on one side of the substrate 40 are electrically connected to particular pads on the opposite side of said substrate. The substrate 40 is of a doublecrossshaped outline and is provided with a central rectangular-shaped aperture.

With reference to Figure 11, the top surface of the uppermost layer of the substrate 40 is provided with pads 50a - 61a. The top surface of second layer of the substrate 40, ie the layer adjacent to the uppermost layer, is provided with a coil section 41a. The bottom surface of the third layer of the substrate is provided with a coil section 41b. The bottom surface of the lowermost layer is provided with pads 50b - 61b. Plated-through holes provide electrical connection between the different layers of the substrate. Plated-through-holes 74 connect one end of the coil section 41a to one end of the coil section 41b. The opposite end of coil section 41a is connected to the pads 55a and 55b by means of plated-through holes 67, and the opposite end of coil section 41b is connected to pads 52a and 52b by means of pl ated-through -holes 65. The remaining pairs of pads on the substrate 40, namely pads 54a&b, 53a&b, 51a&b, 50a&b, 60a&b, 61a&b, 59a&b, 58a&b, 57a&b, and 56a&b are connected by plated-through-holes 66, 64, 63, 62, 73, 72, 71, 70, 68 and 69 respectively, to provide additional by-pass means.

Figure 16 shows a coil configuration using eight stacked substrates 40.

(It should be noted that the magnetic core is not shown.) More specifically, Figure 16 shows, schematically, the end views of the stack and the corresponding circuit diagram. The corresponding reference 11 numerals of the pads on the schematic end views are shown in Figures 14 and 15.

The substrates 40 are stacked so that the orientation of each substrate along the Z-axis is alternated with each successive substrate so that the pads 50a - 55a or 50b - 55b of one substrate are facing pads 56a - 61a or 56b - 61b of an adjacent substrate.

The resulting coil configuration comprises two isolated series pairs on the primary side, namely L2 and L6 and L4 and L8, and on the secondary side one parallel pair L1 and L5 and one series pair L3 and L7. Rotating particular substrates by 180' about the Z-axis alters the connections between substrates and subsequently yields further coil configurations.

Importantly, rotation of a substrate by 180 about the Z-axis only results in change in the coil configuration on one side. For example, rotation of the 711 substrate results in a change in the coil configuration on the secondary side but not on the primary side. Thus a coil configuration on one particular side of the magnetic core can be altered independently of the coil configuration on the other side of the core.

Conveniently, the two possible rotational orientations about the Z-axis may be thought of as binary numbers 1 and 0. Thus there are 16 different coil configurations possible on each side of the core. Assuming a stack of eight substrates, then on each side of the core the coils may be configured as two isolated series, two isolated parallel pairs or an isolated mixture of one series pair and one parallel pair.

One important advantage of the substrate 40 is that a stack of such substrates does not require any external wiring to and from different parts of a stack of such substrates. The substrates 40 allow for external connection to be made through the pads on an end substrate of a stack.

12 The corners provided by the double-cross-shaped outline of the substrates 40 facilitates that stage of assembly when the stack is dipped into solder pot so as to provide interconnections between facing pads.

It will be appreciated that different ranges of substrates are possible by 5 altering the number of electrically conductive pads according to the number of substrates envisaged in a stack.

As should now be evident, another important advantage of the substrates 1 and 40 is that choke and transformer configurations can be assembled to a designer's specific requirements. The substrates also incorporate all the advantages of printed circuit boards coil windings in relation to high frequency power and pulsed applications, for example, more efficient use of core winding space when skineffect losses and power dissipation capabilities are taken into consideration and small, more compact chokes and transformers.

Printed circuit board windings also have the advantage of far tighter tolerances on electrical characteristics influenced by manufacturing variation, ie inter-winding capacitances, leakage inductances and DC resistances.

Furthermore, errors in numbers of turns introduced during manual winding are also eliminated.

13

Claims

1. A substrate comprising a length of coil winding, and the substrate being so arranged that, in use, a plurality of said substrates may be stacked so as to form a desired coil configuration.

2. A substrate as claimed in claim 1 in which the substrate comprises contact means, said contact means being arranged to at least partially provide electrical connection between at least two substrates in a stack of such substrates.

3. A substrate as claimed in claim 2 in which the contact means at least partially provides electrical connection between adjacent substrates in a stack of such substrates.

4. A substrate as claimed in claim 2 or claim 3 in which the contact means comprises at least one electrically conductive feature provided on one side of the substrate.

5. A substrate as claimed in claim 4 in which at least one electrically conductive feature is provided on each side of the substrate.

6. A substrate as claimed in claim 5 in which at least one electrically conductive feature on one side of the substrate is electrically connected to at least one electrically conductive feature on the opposite side of the substrate.

7. A substrate as claimed in claim 5 or claim 6 in which at least one electrically conductive feature on one side of the substrate is connected to at least one electrically conductive feature on the opposite side of the substrate by a length of coil winding.

14

8. A substrate as claimed in any one of claims 2 to 7 in which the contact means is disposed so as to register with contact means disposed on a facing side of an adjacent substrate in a stack of such substrates.

9. A substrate as claimed in any one of claims 4 to 7 in which the at least one electrically conductive feature comprises an electrically conductive pad.

10. A substrate as claimed in any one of claims 2 to 7 in which the contact means is formed at least in part by the process of screen printing.

11. A substrate as claimed in any preceding claim in which the length of 10 coil winding is formed at least in part by the process of screenprinting.

12. A substrate as claimed in any preceding claim in which the substrate is provided with an aperture which is suitably dimensioned so as to accommodate a magnetic core component.

13. A substrate as claimed in any preceding claim in which the substrate is provided as a piece of printed circuit board.

14. A substrate as claimed in any preceding claim in which the substrate comprises multi-layer printed circuit board.

15. A method of stacking substrates so as to achieve a desired coil configuration, wherein the substrates comprise a length of coil winding.

16. The method as claimed in claim 15 in which the substrates are stacked so that alternate substrates correspond to respective coils in at least part of the coil configuration.

is

17. The method as claimed in claim 15 in which the substrates are stacked so that adjacent substrates correspond to a respective coil in at least part of the coil configuration.

18. The method as claimed in claim 15 in which the substrates are stacked so that alternate substrates correspond to respective sides of a magnetic core in at least part of the coil configuration.

19. A coil configuration comprising a stack of substrates, the substrates each comprising a length of coil winding.

20. A substrate substantially as described herein with reference to 10 Figures 1 and 2 of the accompanying drawings.

21. A substrate substantially as described herein with reference to Figures 11 to 15 of the accompanying drawings.

22. A stack of substrates, each substrate being as claimed in any of claims 1 to 14.

23. A stack of substrates substantially as described herein with reference to any of Figures 3 to 10 of the accompanying drawings.

24. A stack of substrates substantially as described herein with reference to Figure 16 of the accompanying drawings.

25. A method of producing a coil configuration substantially as 20 described and shown in the accompanying drawings.