Metal fusion bonding – Process – Plural joints
Patent
1998-11-06
2000-11-14
Ryan, Patrick
Metal fusion bonding
Process
Plural joints
228259, 228119, B23K 3102
Patent
active
061457337
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method for soldering additional electronic components to a circuit board which already has soldered components, wherein the additional components are plugged through the circuit board and soldered thereto.
In order to solder electronic components to a circuit board, conventional technology has utilized the so-called feed-through mounting technique with which thin component connectors, so-called legs, are plugged from one side into holes of the circuit board and connected thereto at the rear side through the introduction of solder. Towards this end, the so-called flow solder method is normally utilized with which the liquid solder, in the form of a wave, is introduced to the rear side of the circuit board. This method has the disadvantage that the circuit board can thereby only be configured at one side.
In addition, the so-called surface mounting technique has been developed with which the components are disposed on the surface of the circuit board and soldered without having to pass through the circuit board. In this manner, the circuit board can be configured on both sides. In this case as well it is possible for the solder to be introduced using the flow solder method however the so-called reflow technique is usually utilized. Paste solder having a resin component is thereby used and therefore simultaneously serves for attaching as well as soldering the components. After introduction of the paste solder, the components are inserted therein and introduced into an oven at the position fixed by the resin component. The paste solder then melts and connects the components to the circuit board.
It is often necessary to retroactively solder additional electronic components onto a circuit board which already has electronic components introduced thereon in accordance with one of the two methods. One therefore has the difficulty, that the subsequent soldering can damage the elements which are already present on the circuit board as well as their soldered connections. This is not acceptable. The subsequently mounted components are therefore plugged through the circuit board in the above mentioned fashion and, connected to the circuit board using single soldering points and soldering regions.
Known in the art from DE 43 14 241 A1 is the effecting of individual soldering points or regions using a small soldered head on the upper exit end of which the solder, in the form of a small wave, overflows so that a so-called mini-wave is formed. It has turned out that this type of small solder head does not effect reliable soldering results, since the solder has a high affinity for oxygen so that impurities in the form of an oxidation layer are often present on the surface of the solder head. This layer is difficult or impossible to remove. In addition, it has turned out that the height of the wave has certain fluctuations. This can encroach upon the quality of the solder joint. In addition, the relatively small amount of solder can lead to an uneven solder distribution.
SUMMARY OF THE INVENTION
The soldering points or soldering regions which are to be subsequently effected are usually unevenly distributed over the circuit board. In the method mentioned, this leads to the additional disadvantage that the circuit board must either be displaced above the solder head during the soldering process, or a plurality of solder heads must be provided corresponding to the number of soldering points to be formed. In the first case, very complicated movements are required, making the method slow and not very effective and the apparatus is difficult to construct and correspondingly expensive. In the second case, the constructional effort is likewise extremely high and there is an unacceptably high risk of poor quality soldering in consequence of impurities in conjunction with the large number of soldering heads.
U.S. Pat. No. 5,176,312 proposes a device for the soldering of electronic components to a circuit board with which the upper side of the soldering bath has an attached nozzl
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Liedke Volker
Streckfuss Herbert
Herbert Streckfuss GmbH
Johnson Jonathan
Ryan Patrick
Vincent Paul
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