Hi Larry,
Did you have these little boards panelized? If so, how did you singulate
them?
The customer's assembly notes contain a lot of the same Invensense notes
and also contain statements like: "IT IS SUGGESTED TO USE PLASTIC/RUBBER
NOZZLES instead of using metal/ceramic pick and place nozzles.
- SHARP AND SUDDEN IMPACTS should be AVOIDED.
- The following Pick and Place parameters are recommended to minimize the
machine impact force on the MEMS device:
a. MOUNTER TRANSFER MAX SPEED: 50cm/s
b. MOUNTER MAX FORCE: 480GF or 4.7N
C. AS A GOOD PRACTICE, SET UPH (Units Per Hour) OF SMT AS <60% OF IT'S
DESIGNED SPEED. (example: Panasonic NM-EJMTD designed speed: 35.8k
Units/Hour)" and: "PCBs that incorporate mounted sensors SHOULD NOT BE
SEPARATED BY MANUALLY SNAPPING APART. This could also create g-forces in
excess of 10,000g. (Laser cut should be a good practice). Their notes also
contain a statement that manual soldering should be avoided.
I can't find out how these InvenSense motion sensors are constructed, but
it's probably the same sort of construction that the IPhone motion sensor
is, which is a vibrating fork gyro, here's an IPhone 4 gyro:
https://d3nevzfk7ii3be.cloudfront.net/igi/UurGsklhtJRW2uuB.huge
Obviously there needs to be some pretty specialized processes set-up when
you are building boards with these motion sensors that I will need to
account for in my labor quotes.
Steve
On Thu, Sep 20, 2018 at 9:37 AM Larry Dzaugis <[log in to unmask]> wrote:
> Assembled similar small boards.
> Had 11" reeled components. Had to cushion any location where they were
> stored on the side.
> Had difficulty getting the factory to treat then as delicate parts.
> All assemblies were trayed for handling.
> It was a no clean process for automotive.
>
>
> On Thu, Sep 20, 2018 at 11:26 AM Stadem, Richard D <
> [log in to unmask]>
> wrote:
>
> > I worked on the development of MEMS gyro components for Honeywell and
> > Benchmark 15 years ago. They are indeed extremely sensitive components,
> > measuring and controlling pitch, yaw, and thrust on avionics. They are
> > actually a miniature spinning gyroscope on a gantry, and the gantry
> > measured the interial forces of the spinning gyro. We initially had a
> high
> > fallout of these components but had great difficulty testing them at
> > different stages of the process to determine where the shock/vibration
> was
> > occurring that caused them to fail. So I assembled a shock/vibration
> reader
> > to the output of the MEMS and attached it directly to the CCA, which in
> > turn transmitted a Bluetooth signal to a data receiver/recorder. I
> tracked
> > the shock/vibe on a sample of three parts from Honeywell's factory
> through
> > the delivery truck through all of the manufacturing processes. It was
> clear
> > we were looking for a process that delivered steady-state or at least
> > re-curring vibration of such intensity that a sudden drop/upward shock or
> > huge thrust coupled with high inertial forces was causing the failures,
> as
> > seen by 500x views of the damaged areas. The three samples tracked very
> > similarly throughout their life from fabrication through final
> > assembly/inspection. I could only track one at a time, but all three
> > recorded the greatest shock and either partial/intermittent failure or
> full
> > failure after the in-line wash process. The cavitation of the wash water
> > sprayers caused all three to fail, and were the greatest shock/vibration
> > readings in their short little lives. So we changed to a different
> assembly
> > process, putting the MEMS on after all other processes were completed and
> > used a manual wash process with full blow-off and a short bake for 15
> > minutes at 105 C.
> > No more failures.
> > Changes were made to the physical design of the MEMS at that time, and
> for
> > all I know that could be the component you are dealing with today. Or it
> > may be something entirely different. But I do know this; the wash process
> > can be very destructive on MEMS components for the reasons stated above.
> > Odin
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> > Sent: Thursday, September 20, 2018 9:18 AM
> > To: [log in to unmask]
> > Subject: [TN] 6-axis MEMS Gyroscope/Accelerometer assembly
> >
> > Good morning everyone,
> >
> > We're quoting this little 1.5" X 2.5" assembly that has a TDK/InvenSense
> > 6-axis MEMS Gyroscope/Accelerometer on it (PN# ICM-20648). I've not
> > assembled a board with one of these devices on it before. When I read the
> > datasheet, and then the handling guidelines for these parts (
> >
> >
> http://www.invensense.com/wp-content/uploads/2015/02/InvenSense-MEMS-Handling.pdf
> > ) I was quite surprised how fragile these things are seeing how they are
> > primarily used on wearable devices where they are going to see a lot of
> > shock. Yeah I know it is a MEMS part, but it would seem to me if it can
> > survive all the abuse it will see being in a wearable device that it
> would
> > be a little more robust during assembly.
> >
> > So have any of you who have placed these sort of devices, have to make a
> > bunch of changes in their standard assembly processes and stockroom
> > handling practices to accommodate these parts?
> >
> > Thanks in advance,
> >
> > Steve
> > --
> > Steve Gregory
> > Kimco Design and Manufacturing
> > Process Engineer
> > (208) 322-0500 Ext. -3133
> >
> > --
> >
> >
> >
> > This email and any attachments are only
> > for use by the intended
> > recipient(s) and may contain legally privileged,
> > confidential, proprietary
> > or otherwise private information. Any
> > unauthorized use, reproduction,
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> > disclosure of the contents of this
> > e-mail or its attachments is strictly
> > prohibited. If you have received
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> > sender immediately and delete the
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> >
>
--
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133
--
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