editor's blog
Subscribe Now

An Acid Trip

When you think of a high-acid environment, what do you think of? That can of soda? Lemon juice? Your stomach? Battery acid? Well, to review, neutral pH is 7. Your stomach will have a pH of 1.5 to 3.5, presumably depending on how much soda or lemon juice or Thai-spicy tom yum gai you just had. Coca-Cola Classic is around 2.5. Lemon juice: 2.0. Battery acid: 1. It’s hard to imagine electronics functioning in a bath of any of those tongue ticklers.

But there’s an environment that’s even worse. One within which an electronic component must operate. And you might never expect it. In fact, many folks didn’t expect it. It can have a pH of 0.5 or less. It’s car exhaust. And it’s not all gaseous. It can make mincemeat of your chip in a couple months. Who knew…

Certainly not the many folks trying to build pressure sensors for that environment. Sensata has just announced a relative pressure sensor for this application – and even they didn’t realize this when they started.

There are actually a couple things that they’ve done that others have had trouble with. One is simply getting this to work in such an environment; the other is doing it with a single element – other folks apparently use two pressure sensing elements (and measure the difference between them).

The Sensata approach is a two-port sensor, with one sealed port on each side of a piezo-resistive element. Each port exposes the pressure of one of the environments to be compared, so the element is, by definition, providing the relative pressure difference. The element, which, of course, has a backside etch so the membrane is accessible to front and back, is mounted in a ceramic carrier.

Then there’s the bit about the acid. There are lots of things that can be attacked, most of which are on the logic that makes sense out of the raw pressure measurement. In other words, CMOS. Much of it can be protected by suitable passivation, but you still have to get the signals in and out, and that takes metal. And, no matter how much you protect everything else, that metal isn’t going to like lots of acid.

So rather than having that logic on the same chip as the element or an ASIC collocated with the element, they put the ASIC away from the element, outside of the corrosive environment. That minimizes the part that has to be robust and protects the delicate bits.

You can find more in their release

Leave a Reply

featured blogs
Feb 8, 2023
Part of the PCIe 6.0 specification, learn how the TEE Device Interface Security Protocol (TDISP) secures I/O virtualization & enables secure key exchange. The post New PCIe TDISP Architecture Secures Device Interfaces with Virtual Servers appeared first on From Silicon ...
Feb 8, 2023
At the recent Chiplet Summit, there was a panel session on the last afternoon titled How to Make Chiplets a Viable Market . The panel was moderated by Meta's Ravi Agarwal, and the panelists were (from left to right in the photo): Travis Lanier of Ventana Micro Systems......
Jan 19, 2023
Are you having problems adjusting your watch strap or swapping out your watch battery? If so, I am the bearer of glad tidings....

featured chalk talk

Faster, More Predictable Path to Multi-Chiplet Design Closure

Sponsored by Cadence Design Systems

The challenges for 3D IC design are greater than standard chip design - but they are not insurmountable. In this episode of Chalk Talk, Amelia Dalton chats with Vinay Patwardhan from Cadence Design Systems about the variety of challenges faced by 3D IC designers today and how Cadence’s integrated, high-capacity Integrity 3D IC Platform, with its 3D design planning and implementation cockpit, flow manager and co-design capabilities will not only help you with your next 3D IC design.

Click here for more information about Integrity 3D-IC Platform from Cadence Design Systems