Advantages of an automated SMT PCB Assembly manufacturing process The process of
prototype PCB Assembly requires multiple phases and a large number of steps. The
process starts with the specification of the design, then proceeds through
electrical design (normally done with a schematic or similar symbolic notation),
into the physical design (layout), PCB fabrication themselves, and finishes in
the assembly of these boards. Errors and mistakes can be induced at any one of
these steps.
With the increase in the number of electronic components
available only in SMT PCB Assembly packages, mounting skills, at least for
prototypes, will continue to move away from the realm of hand or through-hole
assembly.
Hence machine-based SMT PCB assembly is increasingly becoming
a requirement. However, purchasing a pick‐and‐place machine is cost prohibitive.
And even with pick-and-place equipments, there is still the need to stencil the
application of solder paste prior to placing all electronic
components.
The Electronics Assembly Process:
Apply Solder Paste:
in order to start the assembly process, solder paste needs to be added to those
areas of the unpopulated circuit board. Solder paste only goes where a component
must be in electrically conductive contact with a metal landing pad on the board
itself. Typically, this can be achieved with a Solder Stencil. Using the solder
screen placed directly onto the PCB and fixed in the correct position,
afterwards a runner is moved across the screen squeezing a small amount of
solder paste through the holes in the screen and onto the circuit board
16 layer PCB. As the solder
screen has been generated from the printed circuit board files, it has holes on
the positions of the pads, and that way the solder is deposited only on the
designed solder pads.
There are two basic types of solder stencils:
framed stencils for use with the solder paste machinery, and prototype stencils
for hand-mounted prototype PCB assembly of the solder
paste.
Pick-and-Place Components: Pick-and-Place can occur either by
machine or by hand. With hand pick-and-place, a technician uses tweezers to
arrange each component on top of the appropriate bits of solder paste. By the
other hand, with machine pick-and-place, a machine loaded with components picks
the components and places them onto the circuit board. The tension of the solder
paste is enough to keep the components in place.
Heat/Reflow Solder:
After components have been added to the PCB, the next stage of the mounting
process is to pass it through the wave soldering machine. Especially for PCB
Assembly prototypes, reflow soldering is the most common
technique.
more...
flex pcb
留言列表
