WO2010071506A1

WO2010071506A1 - Method and arrangement in a telecommunication system

Info

Publication number: WO2010071506A1
Application number: PCT/SE2008/051464
Authority: WO
Inventors: Mattias Aquilon; Lars-Gustaf Andersson
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2008-12-15
Filing date: 2008-12-15
Publication date: 2010-06-24

Abstract

The invention relates to a fixture (100) for fixing a rod shaped object (102) during soldering of said object. The fixture comprises at least two plates (101), each plate having at least one aperture (105) arranged to receive a rod shaped object having a cross section area that is smaller than the area of the apeture. The plates are arranged at a distance from each other such that the apertures of the respective plates are aligned with each other. The rim of the aperture is provided with spring elements (106) arranged to rest against the envelope surface of an object received in the aperture to provide guidance for said object mounted in the fixture. The invention furthermore relates to a plate element (101) for use in said fixture.

Description

Method and Arrangement in a Telecommunication System

FIELD OF THE INVENTION

The present invention relates to arrangements for fixing a rod shaped object during soldering of the same.

BACKGROUND

Filters are circuits which may be used in communication systems to compensate for disturbances such as e.g. interference, etc. caused by the nature of the transmission media between sender and receiver. Filters remove the unwanted communication signal components and/or enhance the wanted communication signal components.

Radio Frequency (RF) filters and Microwave filters represent a class of filters, designed to operate on signals in the Megahertz to Gigahertz frequency ranges. This frequency range is the range used by most broadcast radio, television and wireless communication systems such as e.g. cellular communication systems, Wi-Fi, WiMax, LTE, etc. Thus most wireless communication devices will include some kind of filtering device performing filtering on the signals transmitted and/or received. Further are filters located in the radio interface communication nodes such as e.g. the radio antenna of the broadcast radio system, the TV broadcasting antenna of the television system and the radio base station of the cellular telephone system. Such filters are commonly used as building blocks for duplexers and diplexers to combine or separate multiple frequency bands.

Today two technologies predominates the radio base station front end filters. These filters, coaxial filters and ceramic filters each consists of a number of resonators, coupled together providing a proper transfer of wanted signals and rejection of unwanted signals.

Ceramic center conductors used for example in frequency filter products, are typically manufactured using high temperature soldering technique. The center conductors comprise of three parts which are soldered together using soldering paste and advanced high temp soldering equipment.

The three parts are typically a flexible washer, a ceramic dielectric rod and a threaded ring. The washer and screw sits on either side of the ceramic dielectric rod with the center lines aligned concentrically.

The ceramic dielectric rod diameters vary due to filter tuning issues but also due to alternative manufacturers, and the concentric alignment between the three parts must be maintained, regardless of diameter value, prior to entering the soldering process.

The speed of the soldering process mainly depends upon the mass of the equipment used i.e. low fixture/equipment mass results in a quicker process. The quality of the soldering process depends among other things on the design of the fixture equipment which affects the possibility for the process vapors to reach the soldering areas and then drain away.

Many existing fixture solutions are not optimal for accommodating varying diameter of the ceramic dielectric rod and at the same time withstand the high temperatures of the soldering process, which may exceed 200 ⁰C.

There are known solutions which comprising designing and manufacturing a soldering equipment/fixture for each ,

diameter variation in order to maintain the concentric alignment condition, using materials that manage such high temperatures. At prototype stage, a separate equipment for each diameter would be acceptable, but at a more serial production like stage, one equipment per diameter is not feasible. The need for a high quantity of equipments/fixtures would cause both logistical and economical difficulties.

Other existing equipment/fixture also exhibits problems with the design. For example, if a parting plane of the fixture goes through the alignment plane of ceramic resonators, this makes it very important for the operator to mount the fixture correctly or else the alignment condition will not be fulfilled. The screw mounting is also relatively time consuming.

Another problem with existing fixtures is that they often has quite big mass and is somewhat closed in the design, which slows down the soldering process and reduces quality.

SUMMARY

It is therefore an object of the present invention to provide an improved soldering fixture that solves at least some of the problems mentioned above.

A first aspect of the present invention relates to a fixture for fixing a rod shaped object during soldering of said object, comprising at least two plates, each plate having at least one aperture arranged to receive a rod shaped object having a cross section area that is smaller than the area of the aperture, wherein the plates are arranged at a distance from each other such that the apertures of the respective plates are aligned with each „

other, wherein the rim of the aperture is provided with spring elements arranged to rest against the envelope surface of an object received in the aperture to provide guidance for said object mounted in the fixture.

Thus, due to the resilience of the spring elements, it is possible to use the fixture according to the invention for fixing rod-shaped objects, such as ceramic dielectric rods, of varying diameters within a certain span, without the need for separate fixtures for each diameter of the rod.

Since the at least one aperture has a larger area than the cross section of the rod to be received in the aperture, and only the spring elements are in contact with the rod, the possibility for process vapors to reach the soldering areas and then drain away is improved, whereby the soldering process is quicker.

A second aspect of the invention relates to a plate element for supporting a rod shaped object in a soldering fixture. Said plate element is provided with at least one aperture arranged to receive a rod shaped object having a cross section area that is smaller than the area of the aperture, wherein the rim of the aperture is provided with spring elements arranged to rest against the envelope surface of an object received in the aperture to provide guidance for said object.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings and claims. _c

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description of preferred embodiments as illustrated in the drawings.

Fig.l illustrates a cross section of an embodiment of the fixture;

Fig. 2a illustrates a plate element having spring elements according to a first embodiment of the plate element;

Fig. 2b illustrates a plate element having spring elements according to a second embodiment of the plate element;

Fig. 2c illustrates a plate element having spring elements according to a third embodiment of the plate element;

Fig. 3 illustrates schematically spring elements resting against the envelope surface of a rod shaped object mounted in the fixture;

Fig. 4 illustrates a ceramic center conductor for a frequency filter.

DETAILED DESCRIPTION

The present invention can be exemplified in the following non-limiting description of an embodiment of the invention . In the following example, the rod shaped object to be placed in the fixture according to an embodiment of the invention is represented by a ceramic dielectric rod 102, to be soldered together with a flexible washer 202 and a threaded ring 302 to form a ceramic center conductor for a frequency filter, see Fig. 4. The ceramic dielectric rod according to this example has a circular cross section. However, other shapes of cross sections of a rod shaped object of this type are not excluded. Also, the rod shaped object to be received in the fixture may be any type of rod that is suitable for soldering.

Fig. 1 illustrates a cross section of a fixture 100 according to an embodiment of the invention, having a support structure 107 and two identical thin spring steel plates 101 which are situated at a certain distance between each other. The plates are fixed by means of supporting plates 108 comprised in the supporting structure. The plates 101 are provided with a plurality of apertures 105 arranged to receive a ceramic dielectric rod 102 to provide guidance for said ceramic dielectric rod when mounted in the fixture for soldering the ceramic dielectric rod and the flexible washer and the ring together. The rim of each aperture 105 of the plates 101 is provided with radially protruding spring elements 106 intended to rest against the envelope surface of the rod 102 as illustrated in Fig. 3, to fix the object in correct position. In this example, the correct position is concentrically aligned with the washer and ring. In order to align the rod concentrically to the other parts, the support structure 107 is provided with guiding means such as apertures 103, 104 for receiving the washer and the ring and fixing them concentrically to the rod received in the fixture. Fig. 2a illustrates a plate element 101 according to an embodiment of the invention. The plate is provided with a plurality of adjacent circular apertures 105, each one arranged to surround a rod shaped object such as the ceramic dielectric rod 102 referred to in the example above. The rim of each aperture 105 is provided with evenly distributed, radially protruding quadratic plate springs 106 intended to rest against the envelope surface of the rod 102, as illustrated in Fig. 3. The spring elements of the plate allow a variation in the diameter of the object, e.g. the ceramic dielectric rod 102 within a certain span, due to the flexibility of the spring elements 106. The geometry of the spring elements may be varied in order to achieve different flexibility properties and hereby adjust the span of different diameters of the objects that may be received in the fixture. In the embodiment shown in fig. 2a, the spring elements are constituted of rectangular plate springs. For example, in order to increase the deflection resistance, such plate spring could be provided with a base at the rim of the aperture that is wider than the end intended for contact with the rod shaped object, see Fig. 2b. Such shape of the spring elements would increase the resistance of the spring, which means that a larger diameter span of the objects is possible. According to yet another possible embodiment, shown in Fig. 2c, the plate springs are arranged to have different protruding lengths from the rim, such that every second plate spring has a certain length that is different from the plate spring in between. This may be done independent of the actual shape of the spring, e.g. it may be quadratic as in fig. 2a or have a wider base as shown in Fig.2b. The purpose of the arrangement in Fig. 2c is also to increase the possible diameter span of the objects to be mounted in the fixture. g

In the embodiments shown in Fig. 1, Fig. 2a-c and Fig. 3, the spring elements 106 are constituted of plate springs that are integral parts of the plate element 101 itself. Thus, the plate element should consist of a material with sufficient resilience and capability to withstand the high temperature that arises during the soldering process, i.e. temperatures that may exceed 200⁰C. I a specific embodiment, thin spring steel plates with a thickness of about 0, 1 mm are used. It is however not excluded that other types of spring elements could be used, such as for example coil springs or pads of resilient material.

In the embodiments described in the foregoing, the apertures 105 of the plate elements are circular in shape, arranged to receive rod shaped objects having circular cross section. However, it should not be excluded that the apertures may have different shapes to accommodate for rod shaped objects having different cross sections.

Thus, due to the spring elements, it is possible to align a rod shaped object such as a ceramic dielectric rod within a span of diameters to other parts of an assembly, e.g. a ceramic center conductor assembly, in a high temperature soldering process. This means that one single fixture can be used for producing many different ceramic center conductor variants having different accuracy in production.

After completion of the soldering, the objects held in the fixture may easily be withdrawn or pushed out of the fixture without the need for opening the fixture. Furthermore, there is no need for mounting screws. Thus, the fixture according to embodiments of the invention provides for easy and rapid mounting and dismounting of the object held in the fixture. Also, the open design according to embodiments of the invention and the fixture's lack of a partiting plane means that the risk of solder residues building-up in the fixture is eliminated or at least reduced. This provides for an accurate centering of the object in the fixture, which leads to a high soldering quality and accurately aligned parts.

Furthermore, the open design provided by the use of spring elements reduces the contact surface between the fixture and the rod, which means that the possibility for the process vapors to reach the soldering areas and then drain away solder residues is improved compared to conventional closed design fixtures. Thus, the open design according to embodiments of the invention leads to shorter soldering time and better quality of the soldered assembly due to less solder residue. The soldering quality thus also affects the performance of a filter comprising ceramic center conductors manufactured in a fixture according to embodiments of the invention, since the use of the fixture provides cleaner ceramic dielectric rods, i.e. with less solder residues remaining.

The open design and the use of thin spring plates in accordance with embodiments of the invention also leads to a fixture with relatively low mass compared to conventional fixtures. This is beneficial since the mass of the fixture influences the capacity of the soldering device to be used. Typically, the capacity of the soldering device is limited to a certain mass of the total set to be soldered, and by keeping the mass of the fixture low, the number of objects that can be accommodated in the fixture to be soldered simultaneously can be increased.

These benefits taken together lead to improved production economics. The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive.

Claims

1. Fixture (100) for fixing a rod shaped object (102) during soldering of said object, characterized in at least two plates (101), each plate having at least one aperture (105) arranged to receive a rod shaped object (102) having a cross section area that is smaller than the area of the aperture, wherein the plates (101) are arranged at a distance from each other such that the apertures of the respective plates are aligned with each other, wherein the rim of the aperture (105) is provided with spring elements (106) arranged to rest against the envelope surface of an object received in the aperture to provide guidance for said object mounted in the fixture.

2. The fixture (100) according to claim 1, wherein said spring elements (106) are constituted of plate springs protruding radially from the rim of the aperture (105) .

3. The fixture (100) according to claim 1 or 2, wherein said spring elements (106) are formed as an integral part of the plate.

4. The fixture (100) according to any of claim 1-3, wherein the at least two plates (101) are constituted of steel spring plates.

5. The fixture (100) according to any of claims 1-4, wherein said at least two plates (101) are provided with a plurality of apertures, such that each aperture (105) of a first plate is aligned with a corresponding aperture of a second plate.

6. The fixture (100) according to any of claims 1-5, wherein said at least one aperture (105) is circular.

7. The fixture (100) according to any of claims 1-6, wherein said spring elements (106) are evenly distributed around the rim of the aperture (105) .

8. A plate element (101) for supporting a rod shaped object (102) in a soldering fixture, characterized in that said plate element (101) is provided with at least one aperture (105) arranged to receive a rod shaped object (102) having a cross section area that is smaller than the area of the aperture, wherein the rim of the aperture is provided with spring elements (106) arranged to rest against the envelope surface of an object received in the aperture to provide guidance for said object.

9. The plate element (101) according to claim 8, wherein said spring elements (106) are constituted of plate springs protruding radially from the rim of the aperture (105).

10. The plate element (101) according to claim 8 or 9, wherein said spring elements (106) are formed as an integral part of the plate.

11. The plate element (101) according to any of claim 8-10, wherein said plate element is constituted of a steel spring plate.

12. The plate element (101) according to any of claims 8-11, wherein said plate element is provided with a plurality of apertures (105) .

13. The plate element (101) according to any of claims 8-12, wherein said at least one aperture (105) is circular.

14. The plate element (101) according to any of claims 8-13, wherein said spring elements (106) are evenly distributed around the rim of the aperture.