Tekmos' Blog

Since technology and applications seem to advance, it’s only fitting that Tekmos’ qualification testing advances as well. Within the last year, Tekmos has incorporated more reliability and qualification testing in our First Article Inspections, which brings customers more confidence and assurance for our design and manufacturing abilities.

Tekmos uses two generic qualification standards; MIL-STD-883 and JESD47. Both of these standards have compliance testing for the device’s Electrical Capability, Environmental Strains, Life Potential, and Package Assembly Integrity. These tests allow the device to be looked at from all angles and predict whether the device can survive under typical stresses seen in the semiconductor industry. However, some testing is dependent on the final application of the device. If the final application is prone to jolt movements but rarely exposed to alternating extreme temperatures, then a focus on the Package Assembly Integrity testing; I.E. Bond Pull Strength, Bond Shear, and Die Shear, might be more beneficial than the Environmental Strains; I.E. Temperature Cycling. Another testing dependent could be from a Product Change Notice (PCN). If a PCN is sent due to a Wafer Design Change, then it would be more useful to perform Electrical Capability testing rather than Package Assembly Integrity. Of course, if any time a customer desires a full qualification, then Tekmos will be happy to accommodate.

Incorporating these qualification tests has come with learning curves and challenges. One main challenge was our project management process had to be revamped to keep up with the additional testing. Majority of the qualification tests are performed by outside suppliers, which means there needs to be extra precaution on lead-time agreements, material management, cost evaluations, and final review of reports. As the Director of Quality, I have taken these new additions to project management as my responsibility. Within the last few months, I have been beta testing a new tool that captures all steps in the qualification process, as well as tracks lead-times and cost trends. Tekmos is hoping this implementation will reduce human error risks, and accurately assess upcoming qualifications.

A key player in our Qualification Testing has been our Product Engineer, Zachary Kolb. He was hired back in April of 2019 and has been the main person involved in First Article Inspections. Along with receiving my many pestering, if not annoying emails and phone calls, he is the mastermind behind the qualification tests performed at Tekmos. He is responsible for coordinating information and material with our suppliers, setup and testing of inhouse qualifications, and report generating. He has been a great asset to Tekmos and continues to help maintain structure and organization in device qualifications.

Kelsey Casto, Director of Quality

Adrian DeLeon is the Post Manufacturing Test Floor Manager for Tekmos, a highly focused, and challenging leadership position in an often-fast paced environment. He is accountable for managing communications with test floor crew, production, customer service, and operations of schedules and systems that guarantee inventory control, finished goods, shipping of products, and an overall effective and efficient production flow.

2020 is his 6th year at Tekmos. Adrian was sought out by the Vice President of Operations after meeting at one of the elite trainings the Boy Scouts of America has to offer, the Wood Badge. Adrian is an Eagle Scout, the highest rank in Boy Scouts of America, a distinction that several Tekmos Team members hold including President Lynn Reed. Adrian has also earned every merit badge, an accomplishment in itself. Only 4% of Boy Scouts have achieved this rank since its inception in 1911.

Some of the priorities of the test floor include: Managing and ensuring safe, quality test floor operations for the testing and programming of various semiconductors, microcontrollers and microchips. Other priorities include the enforcement and maintenance of quality control and environmental industry-respected best practices to meet customer, and applicable regulatory requirements.

Tekmos uses several types of machines needed in Fabless facilities, such as hot and cold temperature forcing probes, bake ovens, gravity-fed MCTs, an automatic multitester, a pick-and-place Aetrium, V-Tek Tape & Reel machines, and the newest machine, the Exatron pick-and-place handler.

Tekmos uses ATEs to reduce manufacturing costs, improve yield, and specifically to prevent defective devices ending up with consumers. Tape and reel equipment as the name implies, is the equipment used in packing and sealing finished products into individual pockets of a carrier tape, and in rolling this tape onto a reel. Tekmos uses tape and reel when a customer requires it as well as for large quantity part orders. Taping and reeling is an alternative packaging process for small surface mount devices that are impractical to ship in tubes. Tekmos ships parts in tubes, tape and reel and other packaging when required.

Tekmos has introduced a new and exciting development in our production. With the start of several government contracts we have been given the opportunity to expand our product reliability and dive into military level testing. Zachary Kolb was hired and brought onto the Tekmos team to take the lead on our new level of reliability testing.

There are several types of testings we have begun that follow the Department of Defense Test Method Standards for Microcircuits (MIL-STD-883). Some of these methods are not done in house and are sent off to our local reliability counterpart, Criteria Labs who are do tests such as UHAST, Vibration Frequency, and temperature cycle tests.

One of the test methods from the MIL-STD-883 we have now begun to use is placing all production parts under a seal/leak test. Once completed and retuned we re-test these parts on sight for a final inspection before they are sent out the door.

One of the central tests we use in house to measure product reliability is a Tri-temperature parametric testing. When our microcircuit has been released as a production part our AC and DC parameter tests are also released. In turn, we take our device and place it on our DUT board and then put them under temperature using a temptronic thermostream. We then cool the device under test to -55 degrees C and allow our AC and DC parameters/patterns to run through the part.

Once tested we can then see the effects that the lower temperature has on the timing of our devices. With the same thermostream we can test the same device at 125 degrees Celsius. We then compare both temperatures to our room temperature, 25 degrees’ Celsius test. At that point, we are able to identify how various temperatures effect our parametric tests and justify the amount of stress we can have on our products while they are still capable of passing within an acceptable parametric limit. Testing these functional tests at multiple temperatures allows us to conform to MIL-STD-883 for Tri-temp testing.

Over the summer we rolled out an Enterprise Resource Planning (ERP) system. The aim of this system is to automate many of the day to day tasks we deal with at a company level and reduce the chance of miscommunication between employees.

The system we use is broken down into “Projects” and “Issues”. A Project is what the bigger picture would be, for example, travelers, new engineering test releases, sales orders, etc. An Issue is a single instance of the project, such as a single traveler for a specific part, a new test for a part, or a sales order. Although our ERP system is still a work in progress, we have currently moved our traveler system for testing parts to a digital system and as a result have improved productivity by streamlining the process.

To accomplish the traveler system, multiple databases have been created that contain our commonly used setups for hardware, software, and testing. This information is then automatically populated into the travelers. This allows the test engineers to speed up the initial stages by having all the information they need available to them instead of having to ask the engineers for the appropriate setup information. We have also integrated several tablets into the system to allow for the digital traveler to travel (move) with the parts from station to station, in a way similar to how the paper travelers moved with the parts.

The databases from the travelers play into the engineering test releases as well. Prior to this system there was never a clear database that was updated with all the approved hardware configurations. When the engineers completed tests, these tests were released to their standards without a universal internal standard. To help with the population of the database another project was created to keep track of these tests.

The sales order Project prompts whomever is processing the customer order for the basic information about the order and then sends this information to the next person to work on the order. After the information is entered into the system, an automatic email is generated and sent to the customer informing them that their inquiry has been received and an update with specifics about their order being processed will be sent soon. With this system all of our sales orders are presented in one place with the date they were received and entered, as well as reminders being sent to key people to follow up on the progress of these orders if they aren’t handled in a timely manner.

Tekmos offers Burn-In and Reliability Testing services.  The requirements can vary from part to part, and Tekmos can customize these services to meet your exact needs.

Burn-in

The failure rate of integrated circuits over time follows what is called the "bathtub" curve.  There is a high rate of infant mortality initial failures.  Then the failure rate drops, only to increase at the end of life due to wear out failures.  The reliability of a part can be enhanced by providing a burn-in at elevated temperatures prior to usage.  This burn-in is typically somewhere from 40 to 160 hours in length, and is done at a temperature of between 70ºC and 125ºC.  It is important that the parts be exercised during this burn-in.  It is also good to monitor the part performance during burning, so that the time point of failures can be detected.  That data can be used to set the optimum burn-in length.

One of the major costs of a burn-in is the boards used for the burn-in.  This is a tradeoff between the cost of the sockets on the boards, the number of boards needed, and the total number of parts to be burned in.  Major manufacturers with very high volumes will invest in high quality sockets that will cost from $50 to $100 per chip.  This socket cost adds up quickly.

In addition to the oven capacity, Tekmos also has in-house design and layout capability for both the burn-in boards and driver boards (if needed).

Reliability Testing 

There are several over-lapping reliability testing specifications.  Specifically, these are the JESD47I, the AEC-Q100, and the military Mil Spec 883.  These require subjecting several lots to stresses, and then looking for failures.  Some tests are for the die, and other tests check the packages.  Because of the standardization of the packages, the die tests are the most important.  And the main die test is the HTOL, or High Temperature Operating Life.  In this test, the parts are typically operated at 125ºC for 1000 hours.  If the parts cannot be tested in the oven, the parts will be periodically pulled from the oven, tested, and re-inserted back into the oven.  Common read points are at 48, 96, 168, 250, 500, and 1000 hours.