A substrate (3) and two or more different chips (1a, 1b) having different heating properties (e.g. caused by different dimensions (surface area and / or thickness),
heat capacity (C1, C2), absorptivity,
conductivity, number and / or size of solder bonds) are provided. A
solder material (2) is disposed between the chips (1a, 1b) and the substrate (3). A
flash lamp (5) generates a light pulse (6) for heating the chips (1a, 1b), wherein the
solder material (2) is at least partially melted by contact with the heated chips (1a, 1b). A masking device (7) is disposed between the
flash lamp (5) and the chips (1a, 1b) causing different light intensities (1a, 1b) in different areas (6a, 6b) of the light pulse (6) passing the masking device (7), thereby heating the chips (1a, 1b) with different light intensities (1a, 1b). This may compensate the different heating properties to reduce a spread in temperature between the chips (1a, 1b) as a result of the heating by the light pulse (6). The chips (1a, 1b) may be releasably carried by a
chip carrier disposed between the
flash lamp (5) and the substrate (3) before being positioned on the substrate (3), wherein the light (6a, 6b) of the light pulse (6) transmitted by the masking device (7) is projected onto the chips (1a, 1b) held by the
chip carrier for heating the chips (1a, 1b), releasing them from the
chip carrier and transferring them to the substrate (3), wherein the heated chips (1a, 1b) cause melting of the
solder material (2) between the chips (1a, 1b) and the substrate (3) for attaching the chips (1a, 1b) to the substrate (3).