Tekmos' Blog

Inventory management is a large part of what keeps the manufacturing side running smoothly at Tekmos. Due to the high volume at which parts are manufactured and sold, we require inventory to match up precisely with our accounting software. This is so sales may be able to quote correct quantities available for purchase, as well as start new inventory lots when needed.

At the start of each month, our inventory room and test floor is cross reviewed against our digital backlog and adjusted according to the physical inventory we have on hand. It is my job as the inventory control manager to track down any inconsistencies we have, and correct them. This can consist of entering any missing travelers into our database, converting untested stock to finished goods stock, and removing any parts deemed as rejects due to production failures or other testing.

Often times, our engineers will need various amounts of parts in order to do further testing into the quality and reliability of our microchips, along with other studies. In these instances, we use a logged tracking system to check in/out parts, record where these parts are going, who has them, and whether or not they will be returning to finished goods to be sold.

As our stock levels currently hold over 600 different types of microprocessors for various applications, monthly inventory can seem overwhelming at times. Luckily we have implemented small but impactful changes in the systems we use to make this task a bit easier on everyone. We keep track of our chips using the systems previously described, as well as others such as physically marking inventory boxes to clearly show which parts have had significant movement over the past month, and those that have not.

Another way we maintain and keep a strong hold of inventory is in visibility, segregation, and separation. This focuses on where the parts are in their journey from production to customer and how they are marked along the way.

As a fabless semiconductor company, Tekmos outsources wafer fabrication and device assembly. The decision to outsource testing is more complicated. As a basic philosophy, Tekmos would prefer to do all testing in-house. This is driven by a need to control a major component of the manufacturing and to insure that our customer’s priorities are being met. But we occasionally get either product types or package types which we cannot do in-house, and so we outsource the testing of those parts. The deciding factors are a combination of pin-count and package type.

Our largest tester has 320 data channels and can support parts up to about 400 pins. If the pin count is higher than that, we will have to either design a custom tester, or outsource testing.

The package type and its associated volume is another factor in deciding to outsource. Any part can be manually tested, but manual testing is slow, and so we only use it for low volume parts. Higher volume parts have a lower cost, and are more sensitive to the test cost. Tekmos has a number of handlers, and tape and reel machines, but we don’t have the capability for tray-fed tape and reel. Or at least we didn’t until last month.

In the last year, we have seen a large increase in our consumer products volume. And since most consumer ICs are QFN devices that are sold in a Tape & Reel format, we have needed to increase our T&R capacity. Our current machines are tube fed, but we needed to get one that was tray fed to handle the QFN packages. So, we purchased a second Tape and Reel machine.

Our new machine has a capacity of about 2000 units per hour, which translates to about 15K units per day with a single shift of operation. It also has an optical inspection capability, that checks to make sure that the package is orientated correctly in the tape before it is sealed.

The National Institute for Standards and Technology recently released a set of standards for cyber security. Defense contractors are required to implement these standards by the end of 2017, and that applies to Tekmos. We started off already being compliant with about half of the standards. Achieving compliance with the other half of the standards is more of a challenge.

One major area we are working on is formal documentation. The NIST standards require formal procedures for all aspects of cybersecurity. We already have informal procedures, but converting all of them to formal procedures is a major undertaking. The one advantage to creating all of this documentation is that it fits in with our AS9100 documentation we are creating for our certification audit later on this year.

The second area of work is the addition of card readers to each PC to only allow authorized users on each work station. At first, this seems straightforward, but becomes more complicated when our testers are taken into account. The testers are tightly coupled to engineering, and so are part of our network. But they also run independently, and we have one operator taking care of multiple tester / handler configurations. It is not clear how we will address this.

Another interesting area is the requirement of a whitelist for approved programs. Engineering will frequently try out new programs as part of their jobs. And so the procedures need to be written to allow this, while still providing security.

There is still a lot to do, but we are optimistic that we will be compliant by the deadline. And give the increased cyber threats these days, it is good to be improving our defenses.

Tekmos sells many micro controllers and Flash memories that are in PLCC packages. These mature packages are not being supported by modern handlers, and so we are fortunate to have acquired both a number of MCT handlers, and production kits for packages sizes ranging from 20-pin PLCC up to 84-pin PLCC packages.

While old, the handler is capable of both hot and cold operation, and can test parts at a 1800 uph rate. The handler has a clever mechanism that reverses the part orientation during test. Parts that are fed into the handler with pin 1 first, and leave the handler with pin 1 last. This allows a tube of continuity rejects to be easily retested.

We also use this handler in our programming operations. We pre-program about half of our micro controllers, and to do so, we use the combination of our production tester and the MCT handler.

The MCT handlers are just another capital investment Tekmos has made in order to continue to support mature products.

The temperature forcing probe is a washing machine sized box with an adjustable arm extending from it. At the end of the arm is a small test chamber. The machine can generate a temperature controlled stream of air, with temperatures ranging from -65ºC up to 185ºC. The test chamber is placed over the part, and the air is used to either heat or cool the part. Then we can measure the parts performance at a given temperature. And it has an auxiliary thermocouple that can be placed on the part to precisely control the actual part temperature.

We do this for several reasons. When a new part comes out, we characterize its performance over the intended temperature range. Not only does this confirm the correct operation of the part, it also provides feedback for our design models. We also use the probe when we need to test production parts at temperature and do not have a temperature handler capable of working with a specific package. And finally, we use the probe for failure analysis when a customer reports a problem at a specific temperature.

One issue with the probe is that it will also heat the tester that holds the part. We have learned that the best solution is to use a small extender cable so that the part under test is not directly on the tester. In those cases, where the part must be on the tester, we use sheets of thermal rubber as a top insulator, and then put multiple layers of cardboard under that to protect the tester from overheating. We tried ceramic tiles at one point for the underlying insulation, under the belief that if they worked for the space shuttle, then they would work for us as well. But they did not work as well as the cardboard, and so that is what we use.

The temperature forcing probe is a strong asset allowing us to provide a superior product for our customers.