Displacement of Components and Solder during Reflow Soldering

Abstract

During reflow soldering the applied solder paste is melted and the components, previously placed on the solder paste, move into their final position. This process, however, may be accompanied by various unwanted movements of components and solder. Components may move horizontally along the surface of the board (this is called swimming or floating), or may move vertically and stand on their ends (this is called drawbridging or Manhattan effect). On the other hand, the molten solder may move to places other than those intended, e.g., into metallised holes (PTH) connected to the solder lands, or upwards along component leads away from the joint area; this effect is called solder wicking. Moreover, isolated small solder balls are often found on the board surface after melting of the paste. Experiments show that all these effects depend on the heating method, vapour phase soldering often being the most prone. The driving forces of the displacements can be explained in terms of forces and pressure caused by the surface tension of the molten solder, whereas the observed influences of the heating method are the result of the direction from which the heat is transported to the solder paste to be melted. From this, important conclusions for vapour phase soldering, infra‐red soldering and hot‐belt soldering may be drawn.

Citation

Klein Wassink, R.J. and van Gerven, J.A.H. (1989), "Displacement of Components and Solder during Reflow Soldering", Soldering & Surface Mount Technology, Vol. 1 No. 1, pp. 5-10. https://doi.org/10.1108/eb037658