A few weeks ago, I posted a video of a manufacturing
plant that builds smart meters. It is always cool to watch the automated pick-and-place
machines pick surface mount components from tape reels and precisely place them
on the printed circuit board. This video shows the assembly line for microprocessor-controlled
motor controllers for brushless electric motors at
Castle Creations. Business
development manager Lee Estingoy starts out showing the silkscreening process for
the solder mask, then moves on to the tape reels where the electronic components
are fed to the pick-and-place machine. You get to see the amazing speed at which
the robotic head places the parts onto the PCBs. He tells how a vision system verifies
that each part is the right size and value and is oriented properly for placement.
This particular speed controller has a daughter board assembly that gets inserted
by a separate machine because of its relatively large size and weight. Some parts
still need to be hand-assembled because they do not lend themselves to automated
assembly (although there are machines to do the job if the budget can be justified).
After all the parts are on the board, the assembly is fed into a reflow oven
that melts and then cools the solder paste according to a temperature profile that
has been optimized to assure proper flow and adhesion without thermally stressing
the components or PCB and minimizing residual mechanical stress. A Quality Assurances
operator then does a visual inspection with the help of a computer vision inspection
system prior to applying power during electrical test. This helps avoid failures
due to misalignment and solder bridges between pads, and provides a second level
of component orientation and part number verification. Finally, the ESCs are electrically
tested. You get to see a glimpse of the 3-phase controller waveforms during the
test portion (BTW, I made a short video of the modulated pulse width waveforms that
drive the brushless motor). It's good to see in-house, domestic production!
Many moons ago (early 1980s) while working at Westinghouse (now Northrop Grumman)
in Maryland, I took an in-house course on the new-fangled surface mount components
and what the company was doing to incorporate them into designs. We designed and
built towed sonar arrays and MkII torpedo sensors at the Oceanic Division (Annapolis)
where I worked, and the
Electronic Systems Division (Baltimore) division built airborne
and ground-based radars for the military. In those days, nearly all the manufacturing
was done on site, both electrical and mechanical. One session of the class was spent
on a presentation by engineers who were pioneering one of the first visual inspection
systems for automated assembly. They were developing both the hardware and the software
to do the job. We also were given an introduction to ESD handling procedure necessitated
by the small components and their increased vulnerability to static discharges.
It was not really a problem for the passive components, but in moving to SM packages
for silicon devices, die sizes were shrunk to a minimum (for the day), which made
gate sizes and conductor separation small enough to invite arcs and subsequent damage.
We were on the proverbial bleeding edge.
Update: The video below is gone, but here is a very comprehensive article on
the RCGroups website showing the manufacturing operations at
Castle Creations MAMBA X Brushless Electronic Speed Controllers
(ESC) Assembly This story was originally seen on the
Model Airplanes News website.
Electronic Speed Controller (ESC) Waveform Video
(RF Cafe Video) Here is the R/C airplane it was installed in.
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