Applications of Uncompensated Packaged Sensors

In this interview, AZoSensors talks to Scott Sidwell of Merit Sensor about the capabilities and applications of uncompensated packaged sensors.

Could You Give a Brief Overview of Merit Sensor and the Work That You Do?

Merit Sensor Systems is a subsidiary of Merit Medical Systems, which was established in 1987. In the early 90s Merit Medical was looking for a reliable supplier of pressure sensors for their angioplasty inflation syringes. Struggling to find one, Merit Medical decided to vertically integrate a pressure sensor company. That is how Merit Sensor Systems was born.We still manufacture a lot for Merit Medical and they are still our biggest customer, but we operate independently, selling our pressure sensing capabilities to a lot of other medical and non-medical companies outside of our parent company.

My role here started when I joined the company back in 2003 as the Engineering Manager. We have grown quickly since then. I was responsible for developing new products and implementing a lot of the quality controls we have in our systems, eventually moving into product development.

A few years ago, I moved over to the sales side. My experience in engineering has helped me a lot in sales, because this is a technical sale and I always have to discuss the pressure sensor with engineers.

Instead of travelling with the sales guys, I am now a one-person show who can go and answer a lot of questions and hopefully get the customer on the right path very quickly.

Could You Explain What an Uncompensated Packaged Sensor is?

From an electrical point of view, the uncompensated package is just the Wheatstone bridge. It is the resistor configuration of the sensing element. From a physical, mechanical perspective, the uncompensated package is really just the MEMS sensing element on a ceramic substrate. We use a ceramic substrate because it is so stable over temperature, and very media compatible as well.

An uncompensated package does not require that customers have the capability of picking and placing the MEMS die and doing the wire bonding, which are very expensive and delicate operations. In their manufacturing they just need to connect the sensor to a pressure seal and electrically connect it to the output and the input of the Wheatstone bridge before supplying the power and compensating the output signal however they want to.

What Capabilities Do the RS Series Sensor Have?

The RS Series was born out of the need to have something harsh media compatible in a very small package. The RS Series has an easy to use radial seal type of pressure connection, which is good for this type of sensitive sensing element. The other nice feature of the RS Series, especially for the industrial, consumer, and medical applications, is that it is designed to have this radial seal whilst also being surface mount compatible.

RS Series

The RS Series has six pads on it that can be surface re-flowed in a standard surface mount type of procedure in a surface mount re-flow oven, and re-flowed directly to a printed circuit board.

Do You Have Any Specific Examples of Where This Sensor Has Benefitted the Medical Industry So Far?

The RS Series is very compatible with saline solutions, which are very common in the medical industry. The ease of board mounting it and sealing to it makes it easy to use. It is a simple product for companies that do not want to do their own manufacturing but instead use a lot of contract manufacturers.

We ship the RS Series on tape and reel, designed for low to high volume. We can cover whatever volumes you need and a wide range of pressures for a lot of different applications, before shipping it directly to the contract manufacturer in most cases. Then it is easy for these contract manufacturers, who are not very involved in the design, to follow a simple pick and place procedure and reflow type of process. This allows them to develop the board very quickly, as opposed to other pressure sensors, where you need to solder a cable or do some extra manual assembly that might be required.

That is a Large Advantage that Using Your Sensors Has Over Using Other Sensors in the Market. Are There Any More Advantages of the RS Series Compared to Anything Else that is out There on the Market?

In terms of the media compatibility, the pressure and media contact the backside of the MEMS sensing element, so only the silicon and glass are exposed. This is unique from other technologies, for example, where gel is used to protect the topside of the MEMS sensing element and wire bonds but becomes unstable and breaks down over time.

What is Next for Merit Sensor?

There are a lot of things coming up for Merit Sensor. I think that this type of package will lead us into the manufacture of smaller scale products and more flexibility for the customer, especially in this range of harsh media compatibility, where we are talking about liquids as well as dry, clean air type applications.

The next thing on the horizon for us is to expand the temperature capability of this size of product to -40 to 150 ^oC to make it more suitable for automotive applications. That is the next thing that is on the horizon for Merit Sensor and will be coming out soon.

About Scott Sidwell

Scott joined Merit Sensor in September of 2003. Previous to working for Merit Sensor, he served in a variety of engineering capacities with semiconductor companies, such as ON Semiconductor and Motorola. In his current role he works closely with customers to develop custom sensor solutions and provide technical support.

Scott received an engineering degree (ChemE) and MBA from Brigham Young University. He enjoys volunteering his time and is fluent in Spanish.