 The paste initially adheres components in place by being sticky, it is then heated (along with the rest of the board) melting the paste and forming a mechanical bond as well as an electrical connection.The paste is applied to the board by jet printing, stencil printing or syringe and then the components are put in place by a pick-and-place machine or by hand.A majority of the defects in circuit-board assembly are caused due to issues in the solder-paste printing process or due to defects in the solder paste.