Rework (or
re-work) is the term for the refinishing operation or repair of an
electronic printed circuit board (PCB) assembly, usually
involving desoldering and
re-soldering of surface-mounted electronic components (SMD).
Mass processing techniques are not applicable to single device repair or
replacement, and specialized manual techniques by expert personnel using
appropriate equipment are required to replace defective components; area
array packages such as ball grid array (BGA) devices
particularly require expertise and appropriate tools. A hot air
gun or hot air station is used to heat devices and melt solder, and
specialized tools are used to pick up and position often tiny components.
The
SMD rework Station involve several components, which must be worked on one by
one without damage to surrounding parts or the PCB itself. All parts not being
worked on are protected from heat and damage. Thermal stress on the electronic
assembly is kept as low as possible to prevent unnecessary contractions of the
board which might cause immediate or future damage.
In
the 21st century, almost all soldering is carried out with lead-free
solder, both on manufactured assemblies and in rework, to avoid the health
and environmental hazards of lead. Where this precaution is not necessary,
tin-lead solder melts at a lower temperature and is easier to work with.
Mask and spheres for rebelling and working of SMD
Heating
a single SMD with a hot-air gun to melt all solder joints between it
and the PCB is usually the first step, followed by removing the SMD
while the solder is molten. The pad array on the conductor board should then be
cleaned of old solder. It is quite easy to remove these residues by heating
them to melting temperature. A soldering iron or hot air gun can be used
with desoldering braid.
The
precise placement of the new unit onto the prepared pad array requires skillful
use of a highly accurate vision-alignment system with high resolution and
magnification. The smaller the pitch and size of the components, the more
precise working must be.
Finally,
the newly placed SMD is soldered onto the board. Reliable solder joints are
facilitated by use of a solder profile which preheats the board, heats all the
connections between the unit and the PCB to the melting temperature of the
solder used, then properly cools them.
High
quality demands or specific designs of SMDs require the precise application of
solder paste before positioning and soldering the unit. The surface tension of
the molten solder, which is on the board's solder pads, tends to pull the
device into precise alignment with the pads if not initially positioned totally
correctly. Our () SMD Rework Station is of finest quality with unmatched
features and quality to dominate the industry.