Investigation into the solderability issues in surface mount manufacturing with the use of thermal adhesive underfill.

摘要

This thesis investigated manufacturing considerations required to reliably form solder joints on fine pitch leaded electronic components in instances where thermally conductive adhesive was used to improve heat dissipation from the component. In order to minimize extra steps in the printed circuit assembly manufacturing process, the adhesive was placed prior to the placement of the component on the board. This meant that the adhesive cured as the assembly was heated through the solder reflow process prior to the reflow of the solder. Without the addition of adhesive, the component would provide some degree of self-alignment and settling during joint formation. Once the adhesive had cured, however, self-alignment and settling was eliminated, potentially reducing the likelihood that an adequate solder joint would form.;To investigate the manufacturing considerations involved to reliably produce solder joints with adhesive use two studies were conducted. The first study dealt with the statistical examination of the effects of manufacturing parameters. These parameters included component alignment, adhesive placement, and solder paste placement. The second study dealt with the in-situ observation of joint formation during the reflow process using optical microscopy and the Environmental Scanning Electron Microscope (ESEM).;The findings of the two studies indicated that solder joints could reliably be produced if manufacturing parameters where properly chosen. Since the component was restricted, the most critical aspect was determined to be the placement of sufficient solder paste in the vicinity of the lead where it would readily wet the gap between the board and suspended lead. Both studies included the development of new experimental methods to achieve the aim of the investigation.