Metal working – Method of mechanical manufacture – Electrical device making
Patent
1995-01-19
1996-05-14
Arbes, Carl J.
Metal working
Method of mechanical manufacture
Electrical device making
219 8512, 22818021, 392419, H05K 334
Patent
active
055156053
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention relates to a device and a method for soldering components onto boards wherein the device has at least a preheating zone and a soldering zone and a transport device by means of which the boards can be moved from one zone to the next. In known soldering devices, so-called reflow soldering ovens, the boards are imprinted with soldering paste at the locations provided for the components prior to the soldering process; afterward, the components are placed with their connections on these locations, and the soldering paste is melted in a subsequent heating process, which produces a permanent connection between the components and the board. The heat application process is configured such that the board is heated entirely in linear fashion up to just below the melting temperature of the solder, then briefly heated above the melting temperature and cooled again as rapidly as possible.
Due to different mass/surface ratios of free board regions and locations having bulky components or high component densities, a temperature difference can develop inside a board during heating that may lead to edge regions of the board already being destroyed by overheating, while the regions having bulky components or high component density have not yet reached the melting temperature of the solder. It is already known to heat the board slowly and thus create a temperature balance between hot and cold locations over the board by means of heat conduction over a lengthy period of time. This is, however, unsatisfactory with respect to optimum utilization of the system's capacity. Furthermore, it is known from DE-OS 38 06 753 to scan the board with a sensor or an image-recognition device and purposefully supply heat to individual regions. This system is costly, however, and correspondingly susceptible to interference, and is therefore not suitable for board series that are produced in large quantities.
SUMMARY AND ADVANTAGES OF THE INVENTION
According to the first embodiment of the present invention, there is provided a device for soldering components onto boards, with the device having at least a preheating zone and a soldering zone, a transport device by means of which the boards can be moved from one zone to the next, infrared radiators having longitudinal axes extending in the transport direction which are disposed in the preheating zone, and infrared radiators having longitudinal axes extending transversely to the transport direction which are disposed in the soldering zone, and wherein the radiators radiate essentially diagonally, i.e., inclinedly or obliquely, onto the board surface with their main beam axes.
According to a further basic embodiment of the present invention there is provided a device for soldering components onto boards with the device having at least a preheating zone and a soldering zone, a transport device by means of which the boards can be moved from one zone to the next, infrared radiators having longitudinal axes extending at an angle of preferably 45 degrees from the transport direction disposed in the preheating zone and in the soldering zone such that the longitudinal axes of at least some of the infrared radiators cross and wherein the radiators radiate essentially diagonally, i.e., obliquely, or inclined, onto the board surface with their main beam axes.
In contrast, the advantage of the devices and method of the invention having the features of the independent claims is that less radiation is absorbed at the board surface than on the side walls of the bulky components or in the regions having high component density. In this way it is accomplished that heat is supplied exactly to where it is needed.
The cross-type arrangement of the infrared radiators extending lengthwise or transversely permits, in a simple manner, each point or each vertical wall on the board surface to be heated evenly.
Advantages embodiments of the invention according to the main claim are possible due to the measures outlined in the dependent claims. In particular, a diagonal, i.e., inclined, posit
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Hartmann Horst-Joachim
Saile Peter
Arbes Carl J.
Robert & Bosch GmbH
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