A project report submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg, in partial
fulfillment of the requirements for the degree of Master of
Science in Engineering.The viability of introducing a Surface Mount
production line is chiefly determined by the
reliability characteristics of the components being
used. Surface Mount Technology (SMT) is entirely new
and although related to traditional through-hole
processes, requires different components, assembly
techniques and design methods. The purpose of the
literature survey is primarily to determine whether
surface mount components meet today's industrial
requirements with respect to their manufacturing
reliability and availability. A brief review of the
evolution of SMT is also presented. This study finds
that the implementation of SMT should be given highest
priority by manufacturing companies in order to
maintain their share of the marketplace.
Surface Mount Technology embodies a totally new
automated circuit assembly process, using a new
generation of electronic comporents: surface mounted
devices (SMDs). Smaller than conventional components,
SMDs are placed onto the surface of the substrate.
From this, the fundamental difference between SMD
assembly and convencional through-hole component
assembly arises; SMD component positioning is
relative, not absolute.
When a through-hole component is inserted into a pcb,
either the leads go through the hales or they don't.
An SMD, however, is placed onto the substrate surface,
it's position only relative to the solder lands, and
placement accuracy is therefore influenced by
variations in the substrate track pattern, component
size, and placement machine accuracy.
Other factors influence the layout of SMD substrates.
For example, will the board be a mixed-print ( a
combination of through-hole components and SMDs) or an
all-SMD design? Will SMDs be placed on one side of the
substrate or both? And there are process
considerations like what type of machine will place
the components and how will they be soldered?
This project describes in detail the processes
involved in setting up an SMT facility. A simulation
program was developed to verify the viability of these
processes. The simulation program was also applied to
an existing SMT facility and together with developed
optimization software, attempted to identify and
resolve some of the major problems. All this was
achieved, and the extent to which simulation could be
used as an efficient production tool, was highlighted.AC201
