IL196614A

IL196614A - Precision fitted electrical connection surface mounted electronic component

Info

Publication number: IL196614A
Application number: IL196614A
Authority: IL
Original assignee: Chelton Telecom & Microwave
Priority date: 2008-01-24
Filing date: 2009-01-20
Publication date: 2013-11-28
Also published as: FR2926949B1; FR2926949A1; IL196614A0; EP2083470A1; EP2083470B1

Abstract

The component has a casing (20) whose base (20b) includes a through hole (38) for each connection contact (35), where the hole opens at exterior of the casing in an external recessed zone of the base. A shoulder of an electrical insulation ring of each contact is stopped against the zone. A small section part of the ring is projected at an interior of the casing via the hole. The small section part, a head (36.2) of a central conductive part i.e. stub, of each contact and a large section part (37.2) of the ring remain at an exterior of the casing.

Description

>.1-|Opi?N 2>D-D Ύ>)ϋΏ ΐΠ3 ONJIIQ ^nwn TQ>n nVWO PRECISION FITTED ELECTRICAL CONNECTION SURFACE MOUNTED ELECTRONIC COMPONENT CHELTON TELECOM & MICROWAVE C: 67682 PRECISION FITTED ELECTRICAL CONNECTION SURFACE MOUNTED ELECTRONIC COMPONENT TECHNICAL FIELD The present invention concerns a surface mounted electronic component (CMS technology) and more specifically a hyperfrequency electronic component such as an isolator and/or a circulator which may be associated to one or several functions such as a filter or a power limiter.

STATE OF THE PRIOR ART In hyperfrequency, circulators are non-reciprocal components with three ports which permit signals to be separated according to the direction in which they spread. For example, they allow signals to be oriented between an antenna and the transmission circuit on the one hand, and the receiving circuit on the other.

Isolators are also non-reciprocal components with two access ports which allow signals to spread according to one spread direction and which prevent them according to the other direction. The main use is the decoupling between a hyperfrequency generator and its load to prevent any return of energy to the generator .

These surface mounted electronic components usually comprise a mechanical housing with a lower section including a bottom and an upper section or cover, that is to contain a resonant electromagnetic cavity, wherein this cavity contains a stack with a central electronic circuit with a ferrite element on either side, at least one mass plan and a magnet. The central electronic circuit comprises for example coplanar strip lines which terminate in as many connection zones as the component has ports.

Connector pins are designed to provide the electrical interconnection of the electronic component with a printed circuit onto which it is to be fitted. These connector pins are connected on one side to a connection zone of the electronic circuit and are accessible on the other side to the outside of the mechanical housing so that they may be brazed onto a track of the printed circuit.

The use of increasingly high frequencies always demands a reduction in the size of the components as their size is inversely proportional to the frequency. Printed circuit boards are also increasingly miniaturised. Hyperfrequency electronic components whose overall lateral dimensions of the housing are around one to two centimetres and whose thickness is less than one centimetre are now used.

These electronic components are fitted onto the printed circuits boards using automated techniques in continuous furnaces for CMS, wherein the entire surface of the bottom of the housing is brazed onto the printed circuit. It is therefore necessary for the components to have a geometry defined as precisely as possible and also for them to be positioned as precisely as possible to obtain a precise and reproducible electrical connection from the central electronic circuit onto the printed circuit. Taking into account the frequencies at which' such components operate and therefore the compactness of the component housing, it is increasingly difficult to position precisely, in the three dimensions, the connector pins so that they are optimally aligned with the tracks of the printed circuit. If the precision is insufficient, this can make the braze fragile and thus reduce the reliability of the assembly. Risks of short-circuits between the tracks of the printed circuit may also occur. Furthermore, impedance ruptures may appear, which leads to significant losses in the hyperfrequency electronic circuit .

The patent application FR-A-2 879 828. discloses a component hyperfrequency with connector pins 1 each formed by a substantially cylindrical central conductive part 10 designed to be connected electrically to a connection zone 3 of the central electronic circuit (not shown) . Reference is made to figure 1 which shows an exploded view of the connector pin 1 assembly with respect the bottom 9 of the housing 2. The central conductive part 10 of the pin 1 is inserted into an electrically insulating element 4, wherein the electrically insulating element 4 is itself inserted into positioning means 5 opposite the edge of the bottom 9 of the housing 2.

In this figure 1, the connector pin 1 is shown with a central conductive part 10 substantially in the form of a nail fitted with a central core 13 that has a head 11 at the end of it. The central core 13 is designed to be connected electrically to a connection zone 3 of the central electronic circuit. This connection may be made at an orifice 8 in the connection zone 3 of the corresponding coplanar strip line. The head 11 of the central conductive part 10 is designed to be connected electrically to a conductive track P of the printed circuit 100.

The electrically insulating element 4 is shown in the form of a substantially cylindrical ring. The positioning means 5 are also in the form of a substantially cylindrical ring. They have two grooves 6, diametrically opposite, directed according to the z axis.

During assembly, the grooves 6 are designed to move into place by gravity in the slides 7 which are attached to the bottom 9 of the housing 2. The positioning means 5 move to block against the bottom 9 of the housing 2. The slides 7 are positioned at the edge of the bottom 9, at the level of the lateral wall of the housing 2. The bottom 9 is cut-out between the slides 7 to allow the head 11 of the central conductive part 10 to protrude beyond the housing 2 so that it may come into contact with the track P. The cut-out has the reference 12.

The revolution axes of the central conductive part 10 and the various rings 5, 4 coincide during assembly. They are directed according to the z axis of the reference mark illustrated in figure 1. The grooves 6 of the positioning means 5 and the slides 7 are also directed according to the z axis. This layout permits the connector pin 1 to be positioned with precision in the x, y planes, which is to say in the plane of the bottom 9 of the housing 2 as well as in the plane of the printed circuit 100, once the grooves 6 of the ring 5 are engaged in the slides 7. The head 11 of the central core 10 then protrudes with respect to the bottom 9 of the housing 2 outside of the housing 2.

However, this structure has a disadvantage for the positioning in height of the connector pin 1, which is to say its positioning along the z axis, transversally at the bottom 9 of the housing 2. If it is not correctly positioned in height, there is a risk that it does not come into contact with the track P of the printed circuit 100.

Indeed, when the electronic component is transferred onto the printed circuit 100, it undergoes a step where it passes through a furnace at a temperature of around 270 °C. Due to the temperature and the braze flux which forms, the electrically insulating element 4 risks sliding in the positioning means 5, according to the z axis, which is to say substantially transversally at the bottom 9 of the housing 2, and to move away from the printed circuit 100. This slide also causes a movement, in the same direction, of the central conductive part 10 also tending to move it away from the printed circuit 100. The electrical contact between the connector pin 1 and the track P is no longer established.

Another disadvantage of this type of electronic component is that it does not satisfy the requirements of electromagnetic compatibility as the bottom 9 of the housing 2 is largely open due to the presence of the cut-out 12. The connector pin 1 is accessible from the inside of the housing 2 even when the housing is sealed and the electronic component is transferred onto the printed circuit 100.

Yet another disadvantage is that the housing is not impervious especially due to the cut-out 12. It may be essential to provide a seal especially if the printed circuit 100 is to be washed after the transfer of the component.

DESCRIPTION OF THE INVENTION The purpose of the present invention is precisely to provide a surface mounted electronic component that is positioned in the three dimensions, and especially in height, that is as precise as possible so as to avoid any risk of separation of the connector pins and the tracks of the printed circuit onto which it is to be assembled.

Another purpose of the invention is to provide an electronic component which satisfies the electromagnetic compatibility requirements.

Yet another purpose of the invention is to provide an electronic component which has an impervious housing .

To achieve this, the present invention proposes a surface mounted electronic component comprising a housing, an electronic circuit located inside of the housing, at least two connector pins designed to provide an electrical interconnection between the electronic circuit and a printed circuit onto which the component is to be assembled. Each of the connector pins features a central conductive part in the form of a nail with a central core to be connected to the electronic circuit and a head, that is to provide an electrical contact with the printed circuit, and an electrically insulating element which surrounds the central core of the conductive part. According to the invention, the electrically insulating element is a substantially cylindrical ring with two parts that have different cross sections which define a shoulder. The housing has a bottom which has a through hole for each of the connector pins, wherein this through hole opens onto the outside of the housing, in a zone that is externally set back from the bottom, wherein the shoulder of the electrically insulating element abuts against the zone that is externally set back, and the part with the smallest cross section of the electrically insulating element, protrudes inside the housing via the through hole, wherein the head of the central conductive part and the part with the largest cross section of the electrically insulating element remains outside of the housing.

Consequently, during a step when the electronic component assembled onto the printed circuit passes through the furnace, by means of the shoulder of the electrically insulating element, the connector pin may not slide transversally at the bottom and the contact with the printed circuit is maintained.

Each through hole is offset with respect to the edge of the housing, which helps to ensure the electromagnetic compatibility of the electronic component. There are no longer the cut-outs on the bottom of the housing which prevent the electromagnetic compatibility. The part with the smallest cross section of the electrically insulating element may block the through hole, which helps to respect the electromagnetic compatibility requirements.

The bottom of the housing may further comprise, a second zone that is externally set back, with a surface area greater than that of the first zone that is externally set back and which encloses the first zone that is externally set back, wherein the first zone that is externally set back has a greater depth than that of the second zone that is externally set back. The second zone that is externally set back is designed to accommodate the braze so that it can wet the head of the central conductive part of the connector pin sufficiently .

The housing comprises a lower section including the bottom and an upper section or cover which may be fixed imperviously to the lower section.

The cover may be glued to the lower section.

Furthermore, it may be fixed with at least one screw to the lower section to improve the mechanical attachment .

The electrically insulating element of the connector pin may be made from a material which has a substantially constant dielectrical constant and that is capable of withstanding the operating temperature, for example, Teflon (registered trade mark) .

The central conductive part of the connector pin may be made, for example, from gold plated copper, or gold plated brass.

The housing may be made, for example, from gold-or silver-plated steel or from an alloy with a coefficient of thermal expansion as low as possible such as Invar, Dilver or Kovar.

The electronic component may be a hyperfrequency electronic component such as a circulator and/or isolator possibly associated to at least one function such as a filter or a power limiter.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood upon reading the description of embodiments provided purely by way of example and in no way restrictively, in reference to the appended drawings in which: figure 1 shows, in an exploded view, a connector pin used in a component of the prior art and its assembly in the housing of the component; figure 2 is an exploded view of the electronic component of the invention; figures 3A, 3B, 3C respectively show, the central conductive part, the electrically insulating element of the connector pin and the connector pin of the electronic component of the invention; figures 4A, 4B are three dimensional views of the body of the component housing according to the invention; figures 5A, 5B, 5C, 5D are top, bottom and cross sectional views of the body of the component housing according to the invention.

Identical, similar or equivalent parts in the various figures described below have the same numerical references so as to make it easier to change from one figure to the other.

The various parts shown in the figures are not necessarily to a uniform scale, to make the figures easier to read.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Reference is now made to figure 2 which shows an exploded view of an example of a surface mounted electronic component according to the invention. It is supposed that in the non-restrictive example described, this concerns a circulator associated to an isolator. It comprises a mechanical housing 20 in two parts: a lower section 20.1 or body and an upper section 20.2 or cover. The inside of the housing 20 helps to define an electromagnetic cavity 21, in the non-restrictive example described, formed by two parts which communicate. In the electromagnetic cavity 21, there is a central electronic circuit 22 comprising for example several coplanar strip lines 22.1 which terminate with connection zones 22.2. The connection zones 22.2 are located outside of the electromagnetic cavity 21 but are still inside the housing 20 however. Several coplanar strip lines 22.1 are shown connected to one another, wherein each section is in part of the cavity 21. These connection zones 22.2 are electrically connected by connector pins 35 on the outside of the housing 20 especially so as to permit the injection and the extraction of signals in the central electronic circuit 22. These connection zones are shown, in the example, by through holes.

In the example described, there are three connection zones 22.2 because the electronic component described is a circulator associated to an isolator. Other components with the same technology could be concerned, which is to say a single cell three port circulator type component, two port isolator associated or not with a power load of 50 Ω, or a circulator and/or isolator type hyperfrequency component that may be associated to at least one function such as a filter or a power limiter.

The body 20.1 of the housing comprises a bottom 20a and walls 20b. The bottom 20a has an inside face 20bi and an outside face 20be. The walls 20a help to define those of the electromagnetic cavity. The body 20.1 of the housing may be obtained by machining a plate, for example made of steel, which is then silver plated. The machining permits the cavity to be defined and to make the through holes. Consequently, the connection between the bottom 20b and the walls 20a is impervious.

The central electronic circuit 22 is sandwiched between "upper" dielectrical ferrite elements 23.1, 23.2 and "lower" dielectrical ferrite elements 24.1, 24.2. There are two ferrite elements on a same level, one at the level of each part of the cavity 21. The upper ferrite elements 23.1, 23.2 are located above the central electronic circuit 22. The lower ferrite elements 24.1, 24.2 are located below the central electronic circuit 22. Two ferrite elements have been shown per level, as in the example a double cell component is described with a circulator associated to an isolator.

Intermediate and lower mass plans sandwich the lower and upper ferrite elements 23.1, 23.2, 24.1, 24.2. There are also two mass plans per level. They are referenced 25.1, 25.2 when called intermediate and are above the upper ferrite elements 23.1, 23.2 and are referenced 26.1, 26.2 when called lower and are below the lower ferrite elements 24.1, 24.2. The lower mass plans 26.1, 26.2 rest on the bottom 20b of the housing, on the inside face side 20bi.

Then above the intermediate mass plans 25.1, 25.2, are two levels of centring mass plans 27.1, 27.2, 27.3, 27.4 superposed which are to house permanent magnets 28.1, 28.2. There are also two centring mass plans per level and two permanent magnets. The permanent magnets 28.1, 28.2 have upper mass plans 29.1, 29.2. mounted on top of them. The electronic part of the circulator and the isolator, which is to say the stack that has just been described that is located inside the housing 20, is stress-mounted inside the housing 20. For this purpose, above the upper mass plans 29.1, 29.2, screwed caps 30.1, 30.2 are fitted in the body 20.1 of the housing 20 so as to seal the two parts of the cavity 21. Finally, above, the cover 20.2 is positioned which seals the housing 20. If the housing is to be impervious, the cover 20.2 is fixed to the body 20.1 imperviously. This may be done by gluing. A glued seal J has been shown which follows the periphery of the body 20.1 of the housing opposite the cover 20.2. To strengthen the mechanical attachment further, an attachment with at least one screw 31 may be provided, which passes through the cover 20.2 and screws into the body 20.1. The cover 20.2 may, like the body 20.1, be made of silver-plated steel.

Connector pins 35 permit a reproducible and sufficiently precise connection to be established in three dimensions, of the coplanar strip lines 22.1 of the central electronic circuit 22 with tracks P on a printed circuit 100.

According to the invention, a connector pin 35 comprises a central conductive part 36 and an insulation ring 37 surrounding the central conductive part 36. Reference is made to figures 3A, 3B, 3C which are substantially to the same scale. The central conductive part 36 of the connector pin 35, shown in figure 3A, is in the form of a nail with a central core 36.1 and a head 36.2. The central core 36.1 has a free end and an end connected to the head 36.2. The central conductive part 36 may be made for example from gold-plated copper, or gold-plated brass.

The insulation ring 37 is shown in figure 3B. This insulation ring 37 is made from a dielectrical material with a substantially constant dielectrical constant that is capable of withstanding the operating temperature (around 280°C), for example, Teflon (registered trade mark) . This insulation ring 37 is substantially cylindrical and comprises two successive parts of different sections which define a shoulder 37a. The part with the smaller cross section is referenced 37.1, the part with the larger cross section is referenced 37.2. This insulation ring 37 is designed to fit around the central core 36.1 of the central conductive part 36, wherein the upper part of the section 37.2 is located on the head side 36.2 as shown in figure 3C.

Reference is now made to figures 4A, 4B as well as figures 5Ά to 5D which are various views of the housing 20. It may be made for example from gold- or silver-plated steel or from an alloy with a coefficient of thermal expansion that is as low as possible such as Invar (steel containing nickel and a little carbon and chrome) , Dilver or Kovar registered trade marks (alloy containing iron, nickel and cobalt) .

The bottom 20b of the housing has a through hole 38 passing through it for each of the connector pins 35. Each through hole 38 is at the level of a zone that is externally set back 20c on the bottom 20b. This zone will be called first externally set back zone 20c when another is introduced. The externally set back zone 20c is accessible from the outside of the housing 20, from the outside face 20be of the bottom 20b. The externally set back zone 20c forms a hollow in the thickness of the bottom 20b of the housing 20 that is only visible from the outside of the housing. The externally set back zone 20c borders the through hole 38. When assembling the connector pin 35, the shoulder 37a of the insulation ring 37 abuts against the externally set back zone 20c of the bottom 20b of the housing 20. The part with the smallest cross section 37.1 of the insulation ring 37 passes through the through hole 38 whereas the part with the largest cross section 37.2 remains blocked outside of the housing 20 by the externally set back zone 20c. The part with the largest cross section 37.2 of the insulating element 37 is housed in the externally set back zone 20c. It is preferable that its height is substantially lower or equal to the depth el of the externally set back zone 20c.

The central core 36.1 thus penetrates the inside of the housing 20 through the bottom 20b so that its free end comes into electrical contact with a connection zone. The head 36.2 of the central conductive part 36 protrudes beyond the part with the largest cross section 37.2 of the insulating element 37. It is also on the outside of the housing 20, and projects from the bottom 20b of the housing 20 towards the printed circuit 100, when the electronic component is fitted onto the printed circuit 100. The head 36.2 may thus be wetted by the braze. This braze extends over the entire bottom of the housing 20, which means that the input/output connections made by means of the connector pins 35 are completely shielded by a complete mass coverage. This aspect helps to obtain the electromagnetic compatibility of the electronic component .

Thanks to the shoulder 37a of the insultion ring 37 and the externally set back zone 20c of the bottom 20a of the housing, no movement according to the z axis of the central conductive part 36 of the connector pin 35 is possible. The electrical contact with the printed circuit 100 is made even after the passage through the furnace. The function of the through hole 38 is to position the connector pin 35 with precision in the xoy plane. The connector pin 35 is thus positioned with great precision in the three dimensions.

With respect to the prior art, the through holes 38 are no longer situated at the periphery of the bottom 20b, they are offset from the edge of the bottom. Furthermore, they are sealed by the connector pin 35, which means that the electromagnetic compatibility requirements are satisfied at least for the bottom 20b of the housing 20.

It is also possible, in the bottom of the housing 20b, at the level of each through hole 38, to provide a second externally set back zone 20d, which has a larger surface area than the first externally set back zone 20c and which includes the first externally set back zone 20c. The second externally set back zone 20d is also accessible from the outside of the housing 20, which is to say from the outside face 20be of the bottom 20b of the housing 20. The depth e2 of the second externally set back zone 20d, with respect to the external face 20be of the bottom 20b is lower than the depth el of the first externally set back zone 20c with respect to the outside face 20be of the bottom 20b of the housing 20. The purpose of this second externally set back zone 20d is to accommodate excess braze when the electronic component is mounted onto the printed circuit 100 and avoid that this braze enters the interconnection holes on the printed circuit. The latter are not shown. The braze brought together at the level of the second outside zone adequately wets the head 36.2 of the central conductive part 36 of the connector pin 35. The reliability of the braze is thus increased .

Figures 4A, 4B are three dimensional views of the lower section 20.1 of the mechanical housing 20, showing the inside face 20bi of the bottom 20b, and the outside face 20be of the bottom 20b.

Figures 5A and 5B are top and bottom views of the lower section 20.1 of the housing 20. Figure 5C shows, in cross section, how the connector pin 35 is inserted into the through hole 38 and how the part with the smallest cross section 37.1 of the insulating element 37 seals the through hole 38. Figure 5D shows the threaded zone 39 in the body 20.1 of the housing 20 which accommodates the screwed caps 30.1, 30.2.

Of course, the electronic component of the invention is not restricted to a single circulator or isolator type hyperfrequency component, as already mentioned, it may concern any surface mounted electronic component which requires good positioning precision for its connector pins.

Claims

1. Surface mounted electronic component comprising a housing (20), an electronic circuit (22) situated 5 inside the housing, at least two connector pins (35) designed to provide an electrical interconnection between the electronic circuit (22) and a printed circuit (100) onto which the component is to be mounted, wherein each of the connector pins (35) 10 comprises a central conductive part (36) in the form of a nail with a central core (36.1) to be connected to the electronic circuit (22) and a head (36.2), which is to provide an electrical contact with the printed circuit (100), and an electrically insulating element 15 (37) which surrounds the central core (36.1), characterised in that the electrically insulating element (37) is a substantially cylindrical ring with two parts (37.1, 37.2) with different cross sections which define a shoulder (37a) , and in that the housing 20 (20) has a bottom (20b) which has a through hole (38) for each of the connector pins (35) , wherein this through hole (38) opens out onto the outside of the housing (20) , in a zone (20c) that is externally set back from the bottom (20b) , wherein the shoulder (37a) 25 of the electrically insulating element (37) abuts against the externally set back zone (20c) , wherein the part with the smallest cross section (37.1) of the electrically insulating element protrudes inside the housing (20) via the through hole (38), and the head 30 (36.2) of the central conductive part (36) and the part with the largest cross section (37.2) of the SR 31396 CS 19 electrically insulating element (37) remains outside of the housing (20) .

2. Electronic component according to claim 1, 5 characterised in that each through hole (38) is offset with respect to the edge of the housing (20) .

3. Electronic component according to any of claims 1 or 2, characterised in that the bottom (20b) of the 10 housing (20) further comprises a second externally set back zone (20d) , with a surface area that is larger than that of the first externally set back zone (20c) and which encloses the first externally set back zone (20c) , wherein the first externally set back zone (20c) 15 has a depth (el) that is greater than that of the second externally set back zone (20c) .

4. Electronic component according to any of claims 1 to 3, characterised in that the part with the 20 smallest cross section (37.1) of the electrically insulating element (37) seals the through hole (38).

5. Electronic component according to any of claims 1 to 4, characterised in that the housing (20) 25 comprises a lower section (20.1) featuring the bottom (20b) and an upper section (20.2) or cover that is imperviously attached to the lower section (20.1).

6. Electronic component according to claim 5, 30 characterised in that the cover (20.2) is glued to the lower section (20.1). SR 31396 CS 20

7. Electronic component according to claim 6, characterised in that the cover (20.2) is attached by at least one screw (30) to the lower section (20.1). 5

8. Electronic component according to any of claims 1 to 7, characterised in that the electrically insulating element (37) of the connector pin (35) is made from a material with a substantially constant 10 dielectrical constant and is capable of withstanding the operating temperature, such as Teflon.

9. Electronic component according to any of claims 1 to 8, characterised in that the central conductive 15 part (36) of the connector pin (35) is made of gold- plated copper or gold-plated brass.

10. Electronic component according to any of claims 1 to 9, characterised in that the housing (20) 20 is made of gold- or silver-plated steel, of an alloy with a coefficient of thermal expansion that is as low as possible such as Invar, ovar or Dilver.

11. Electronic component according to any of the 25 previous claims, characterised in that it is a circulator and/or isolator type hyperfrequency electronic component that may possibly be associated to at least one function such as a filter or a power limiter .