Dec 17, 2013

A New Piezoelectric Oscillator

posted by Bryon Moyer

A few months ago, we looked at Sand 9’s initial announcement. They had laid out 3 families at that point: a basic resonator (TM061), a temperature-sensing resonator (TM361), and a “roadmap” family for temperature-sensing oscillators. Well, they recently announced a new device that goes in yet a new family: temperature-compensated oscillators – the TM651. When chip-scale packaged, they claim it’s the smallest oscillator in the world (although an LGA is also available).

They’ve come out swinging at their performance versus quartz, in particular the latter’s susceptibility to so-called “activity dips,” which we covered in the prior piece. But they’re also comparing themselves to other MEMS – and, in particular, electrostatic – oscillators. They say:

  • The filter and noise are better than any MEMS oscillator and competitive with quartz;
  • They have 250-ps edge rates as compared to about 1 ns for quartz;
  • Their vibration immunity is an order of magnitude better than quartz;
  • They have 1/15th the drift of other silicon MEMS due to their analog compensation, which is smoother than digital;
  • They can achieve higher frequencies without a DLL, which quartz needs for frequencies above 50 MHz;
  • They don’t have quartz’s finicky start-up time (and, apparently, start-up can occasionally fail outright with quartz);
  • They have better electromechanical coupling than electrostatic MEMS devices because they’re piezoelectric (with the presumed effect that the coupling happens intrinsically within the material as opposed to being between two distinct mechanical members);
  • They have larger transduction area, which, counter-intuitively, reduces die area (presumably because of better intrinsic sensitivity);
  • They have no air gaps, vs. those used with electrostatic devices (which goes to coupling efficiency);
  • They operate off of a lower voltage;
  • They have linear power vs. non-linear for electrostatic, giving them better noise performance;
  • They can work with a customer to have the customer’s electronics co-packaged with their resonator for better integration, which isn’t possible with quartz.

That’s a lot of claims.

Their electronics are in the cap wafer. The bonding is done wafer-to-wafer; both the MEMS and ASIC see very high yields (in fact, wafer probing on the MEMS die is done only on a wafer sample basis to see if it looks like there’s a problem with the lot). GlobalFoundries does this for them.

You can read more in their announcement.

Tags :    2 comments  
Dec 16, 2013

Sorting Cells

posted by Bryon Moyer

Lens-free technology has poked its head up in a few places, but one of the more frequent views you may have of it is an application that Imec appears particularly fond of: a cell sorter.

The whole idea behind the contraption is to isolate abnormal blood cells from a sample. So they built a microfluidic device that delivers a flow of blood cells. Each cell passes over a lens-free aperture where a lens-free camera analyzes the interference patterns that the cell creates. That creates a differentiating signal between normal and abnormal cells.

The processing of that signature happens quickly enough that, at the point where the cell has traveled further to a microfluidic crossroads, normal cells can be steered down one channel; abnormal cells down another.

How do you “steer” a cell? Well, the default flow goes one way, and when a faulty cell is detected, at the time it hits the junction, a small heater creates an instantaneous bubble that pushes the cell into the other channel. (You could also actively steer the normal cells with a counter-bubble as well.)

In case that seems like a lot of work, well, it is. They say that they process 20 million images a second.

As I mentioned, they appear particularly proud of this, because it’s presented at numerous different venues, and they’ve invested in marvelous animation to illustrate what’s going on. So if you find yourself at an Imec function, you may also get to see the images. But, to be sure, it’s more than animation. When visiting their facility, this was one of the places they took us where they stood by like proud papas as we took a look at the real deals.

One of the challenges with building something like this is finding an adhesive that is compatible with being a microfluid channel, especially when there may be heaters and such in the device. Such an adhesive would be used to secure a glass cap.

Imec and JSR announced such a material last month. The adhesive can be patterned using normal photolithography, allowing this step to be performed on entire wafers. The picture below shows a cell sorter wafer with glass covers glued to the intact microfluidic dice, which contain those micro-heaters for steering the cells. With glass covers in place, the wafer can be diced up into individual cell sorters.

You can read more about this material in their announcement.JSR_wafer_red.png

Tags :    0 comments  
Dec 12, 2013

Automotive IMU

posted by Bryon Moyer

At the recent MEMS Executive Congress, Bosch Automotive announced a new 6-axis automotive IMU. It’s not for use as part of the automotive control systems, but rather for the “infotainment” infrastructure – the so-called center stack – and other non-safety-critical applications.

It may not be obvious that Bosch has two different sensor groups. There’s an automotive group which focuses strictly on – you guessed it – cars; then there’s Bosch Sensortec, which handles other consumer and industrial sensors. (There’s also Bosch Akustica for microphones.) So… does this mean that Bosch Automotive is off in its private silo inventing its own sensors independently of Bosch Sensortec?

No; according to them, the automotive market actually isn’t large enough compared to phones and other consumer goods to justify that. The IMU that Bosch Automotive has announced actually came from Bosch Sensortec. Does this mean that it’s just a rebranding of an old part?

No; the automotive units have more stringent operating requirements than a consumer unit has. Just going to 125 °C from 85 isn’t trivial. There are also corrosion concerns and the fact that the IMUs must interface with automotive diagnostic systems.

Corrosion can presumably be handled with packaging. Calibration and linearization over a higher temperature range involve changes to the ASIC. The diagnostic interface also resides in the ASIC. So, in reality, we have a Bosch Sensortec IMU with a new ASIC and package.

You can find out more in their release.

Tags :    0 comments  
Get this feed  

Login Required

In order to view this resource, you must log in to our site. Please sign in now.

If you don't already have an acount with us, registering is free and quick. Register now.

Sign In    Register