Starting this report 3Dprinting is explained and the state of the art in 3D printing structuralelectronics. From here the current state of the project is described afterwhich the project goal is formed. The project goal for this project is asfollows:  “Test and prototype on-sitecuring of solder paste on a 3D printed substrate to enable the 3D printing ofstructural electronics in prototypes using an FDM 3D printer”  After the project goal the vision for thefuture 3D printer is also discussed.  ResearchReflow soldering methods used in industry were researched and the mostpromising methods were chosen for the given use case of on-site curing ofsolder paste in a 3D printer. The most promising methods for on-site curing area thermode, a diode laser and focused hot-air. Also the used materials (e.g.solder paste and thermoplastic substrate) are discussed in more detail.  Testing of methods The three most promisingmethods were tried and tested to see which would be the most suitable method tocontinue with. Only the focused hot-air method produced usable results wherethe traces would be conductive.  Hot-airdetailed testing After determining that the focused hot-air method was mostsuitable method more detailed tests were done. Tests were conducted forprinting overlapping traces as a first step in printing in the verticaldirection. Trace pitch was tested for connecting DIP pitch components. As wellas how pins can be connected to the solder paste traces. And lastly tests aredone to quantify the conductivity of the printed and cured solder paste traces.Architecture of the system The system that was used for testing is described indetail. The system consists of a Ultimaker for printing the thermoplasticsubstrate and RepRap printing platform where the custom built solder pasteextruder and focused hot-air gun are mounted in. Design guidelines To use thedeveloped method for future research several design guidelines are described inthis section. First the CAD is discussed with the dimensions of the trace andhow components are to be placed in the design. After that the preparation ofthe Gcode for both printers is described. Demonstrator To demonstrate theabilities of the developed method a demonstrator product was designed and made.This demonstrator combines all the abilities that were tested separately in thehot-air detailed tasting chapter. Conclusions To finish this master thesis itis concluded that using this method of printing and curing as an alternative materialin 3D printing prototypes of structural electronics is promising. It is easy touse and affordable with sufficient quality to be used for prototypes. Howevertrue 3D functionality has not been achieved yet. Recommendations In this masterthesis a step forward has been made for using solder paste in 3D printingstructural electronics. To improve this method more research is needed andpossible steps for future research are discussed here. Creating consistentlayers would open up the possibility of stacking multiple layers and open upthe possibility of printing 3D structural electronics.