NOVELTY - The method for materially connecting a first material such as a connector (10) e.g. copper tape to a second material such as a semiconductor device e.g. a solar cell using soldering by a focused laser beam striking on the first material, comprises regulating the power of the laser beam in dependent of the temperature measured by the heat ray, and determining the temperature from the first material in direction to the laser beam, where the temperature in an area of the first material that is adjacent to it, at which the focused laser beam strikes on the first material, is measured.    USE - Materially connecting a first material such as connector e.g. copper tape to a second material such as semiconductor device e.g. solar cell using soldering.    ADVANTAGE - The method is capable of simply and effectively connecting the first material to the second material with high quality without distortion.    DETAILED DESCRIPTION - The method for materially connecting a first material such as a connector (10) e.g. copper tape to a second material such as a semiconductor device e.g. a solar cell using soldering by a focused laser beam striking on the first material, comprises regulating the power of the laser beam in dependent of the temperature measured by the heat ray, and determining the temperature from the first material in direction to the laser beam, where the temperature in an area of the first material that is adjacent to it, at which the focused laser beam strikes on the first material, is measured. A heat-ray measuring sensor is used for measuring the temperature, where the measuring beam path of the sensor runs parallel or coaxial to the laser beam path before striking on the first material. The laser beam is formed in two compatible spaced foci (26, 28) on the first material and the heat ray is detected as measurement ray by the sensor, where the measurement ray is determined from the area of the first material running between the foci. The heat ray determined from the area of the first material is detected as the measurement ray, which coaxially surrounds a focus of the laser beam formed on the first material. The laser beam formed in a focus on the first material. The heat ray, which is measured in two areas of the first material running diametrically to the focus, is measured as measurement ray. The laser beam is formed on the first material in an annularly running focus area. The heat ray of the first material is measured as the measurement ray, which is determined within the annular focus area. The laser beam or measurement ray is divided over a refractive optical element (24) such as roof prism or axicon, a diffractive optical element or a reflecting optical element. A beam splitter (20) is arranged in the measurement beam path of the sensor and is penetrated for one of the measurement beams and deflects for other laser beam or vice versa. The laser beam is divided or focused, so that the average distance between two foci is 1.0-2.5 mm in a focus diameter of 0.5-1.5 mm by observing areas of the first material uncovered by the foci. An INDEPENDENT CLAIM is included for an arrangement for soldering a first material to a second material.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a first laser beam path.    Connector (10)    Collimator optics (18)    Beam splitter (20)    Refractive optical element (24)    Foci. (26, 28)