The present invention relates to a flexible joint. Specifically, the present invention relates to a flexible joint for radio frequency or DC links between microwave products.
Interlinking tapes are used on a multitude of microwave products. For example, they are used to provide a radio frequency link or DC links between launch pins and substrates. Another example is their use as radio frequency interconnects from substrate to substrate.
The present invention relates to a flexible joint. Specifically, the present invention relates to a flexible joint for radio frequency or DC links between microwave products. The present invention also provides a method for connecting two substrates including the steps of: i) bonding an end of a tape to a first substrate, wherein there is a gap formed between the two substrates and the tape is bonded facing away from the gap; ii) bending the tape towards the gap such that the tape is curved back on itself; and iii) bonding the other end of the tape to a second substrate.
Exemplary embodiments of the present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings.
Referring to
The method/process used to produce these loops 120 employs a 0.25 mm mandrel that is fixed to a ceramic tile. A length of the gold ribbon is placed across the mandrel on the tile, then using cocktail sticks it is fashioned to the shape of the mandrel. Once an adequate shape is produce it is then bonded across the two substrates using a parallel gap welder.
The interconnected substrates are made from alumina and attached to gold plated metal matrix carriers. These are subsequently mounted into a machined aluminum box. The thermal coefficient of expansion of alumina is approximately 8.2×10−6 per ° C. and the carrier is roughly matched to this. The thermal coefficient of expansion, however, of the aluminum box is approximately 23×10−6 per ° C.
Due to the mismatch of coefficients, the gap between the two substrates will vary as the product under goes thermal change. Under ambient temperature, the interconnect 220 remains at the shape it was originally formed, as shown in
The stressing of the joint will cause fatigue of the gold tape 120 despite its ductility and it will deteriorate progressively until it fractures. This is a common problem with this type of interconnect and produces an unacceptable failure rate.
An exemplary embodiment of the present invention will now be described with reference to
Referring to
The two substrates 300, 310 are linked by a interconnect tape 330, which connects the tracks 320, 340 on the substrates 300, 310. The interconnect tape 330 used is 99.99% pure gold ribbon. The tracks 320, 340 are about 20 μm wide so the interconnect tape 330 used is about 20 μm wide by ½ μm in thickness, with a breaking load of about 150-200 g and elongation of 0.5-3%.
By changing the dominant type of stress within the joint, the amount of force seen by the bond can be reduced. Thus, the effect of the movement can be decreased and so the possibility of fracture.
Accordingly, the joint is formed so that it forces a low stress rolling action in the joint material, rather than a high stress bending as in the known horse shoe shaped loop discussed above. When coupled with a very large heel angle, this will improve joint robustness. As seen in
It is worth noting that it is not just the lateral movement alone that causes the fatigue. When a material expands and contracts, every linear dimension increases by the same percentage with a change in temperature, including holes, assuming that the expanding material is uniform. Although the linear movement is predominant because of the longer length, there is also some lateral movement between substrates. Compliance and durability in the lateral planes that are not illustrated are also improved by this design.
Referring now to
Referring to
It is to be noted that the formation of the looped interconnect tape 420 could be done by eye or a mandrel 440 could be used as a former, as in the previous method of bonding described in relation to the prior art.
It will also be noted that this method could be achieved a number of ways depending one which one is the easiest and the most consistent and that the method described above is an exemplary embodiment of the apparatus and method of the present invention.
It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.
Number | Date | Country | Kind |
---|---|---|---|
0714894.3 | Jul 2007 | GB | national |
This application is a United States National Phase Patent Application of International Patent Application No. PCT/GB2008/050642 which was filed on Jul. 30, 2008, and claims priority to British Patent Application No. 0714894.3, filed on Jul. 31, 2007, the disclosures of each of which are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/GB2008/050642 | 7/30/2008 | WO | 00 | 6/14/2010 |