| 摘要 |
A method of preparing a package comprises joining a first and a second piece of material. The first piece of material comprises a multi-layered material that a mechanically stabilizing layer, an electrically conducting layer, and a weldable layer. The mechanically stabilizing layer comprises a carton material. The first piece of material is arranged so that the weldable layer can be melted by supplying energy to the electrically conducting layer. The method further pressing the weldable layer against the second piece of material, and supplying energy to the electrically conducting layer. The energy supply per time unit, to the electrically conducting layer is varied from a maximum value to a minimum value during the period of time in which energy is supplied to the electrically conducting layer. The maximum value is supplied for the initial at least 40% of the period. |
