Metal fusion bonding – Process – Preplacing solid filler
Patent
1995-02-08
1997-08-05
Bradley, P. Austin
Metal fusion bonding
Process
Preplacing solid filler
228 14, 228 41, B23K 100, B23K 306
Patent
active
056533810
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process and/or an apparatus for producing a bonded metal coating.
In the prior art various processes are known for producing bonded metal coatings in the case of which processes the bonded metal coating is applied to a bonding surface galvanically, chemically, by vapour-deposition or by means of screen printing for example. These known processes have proved to be highly cost-intensive both owing to the complex manner in which they are performed and to the expensive apparatus necessary for performing the processes. This leads to the fact that for example the production costs for a chip which can be bonded or also used in the flip-chip process are essentially determined by the costs for producing the so-called "bumps". The costs associated with the production of bonded metal coatings in the field of pilot or small-scale production have a particularly exacerbating effect.
The present invention is based on the object of creating a process and/or an apparatus which enables/enable bonded metal coatings to be produced economically even for pilot or small-scale production.
This object is achieved by a process having the features of claim 1.
In the case of the process according to the invention a solder material constructed so as to form a solder material shaped body is transported with an energy transfer device which is guided in a capillary tube and which acts in the manner of a stamp towards a bonding surface of a substrate and is acted upon with energy by the energy transfer device for shaping and connection to the bonding surface.
In the case of the process according to the invention the energy transfer device is used on the one hand for transporting the solder material shaped body to the bonding surface; on the other hand the energy transfer device is used to transfer the melting energy into the shaped body in order to enable the shaped body to be shaped or the solder connection to be produced between the shaped body and the bonding surface.
As a result of suitable matching of the capillary tube cross-section and the shaped body mass the process according to the invention permits bonded metal coatings to be produced which are defined precisely in terms of size and shape without the complex masks or templates known from galvanic bonded metal coating processes for example having to be used. Moreover it is possible for the first time to process shaped bodies in the form of solder beads for example individually and in a precisely defined size and not, as was conventional hitherto, to use a solder paste in which solder beads are distributed in a manner which differs widely according to their diameters.
It has proved particularly advantageous if an optical fibre arrangement which consists of at least one optical fibre and which is used to transfer laser energy is used as the energy transfer device. This type of arrangement of the energy transfer device makes it possible to introduce in a precisely metered manner the energy required for shaping a shaped body or connecting it to a bonding surface.
In a method of performing the process according to the invention the solder material shaped body is fed to a delivery chamber at the end of the capillary tube in such a way that it is disposed between a bonding end of the energy transfer device and a delivery opening in the capillary tube before being bonded to the bonding surface. This alternative offers the possibility of processing prefabricated shaped bodies which are defined exactly in terms of shape and size.
In a further method of performing the process the solder material is fed in continuous form, for example as solder wire, to the delivery chamber at the end of the capillary tube in such a way that one end of the solder material projects into the delivery chamber formed between a bonding end of the energy transfer device and a delivery opening in the capillary tube such that the shaped body is formed as a result of energy acting on the end of the solder material during the course of a remelting process which occurs in the deliver
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patent: 5421504 (1995-06-01), Spirig
Bradley P. Austin
Fraunhofer-Gesellschaft Zur Forderung der Angerwandten Forshung
Knapp Jeffrey T.
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