Process Improvements for First Pass Yield Gains during Tri-Temperature Automotive Package Test
Authors: Broz Jerry J. , Humphrey Bret A. 
Published: January 2025

Test requirements for components within automotive electronics systems have strict quality standards. With the continuous growth of high performance and critically reliable devices for navigation control, infotainment, collision detection, and ADAS there are significant requirements for stable package-level-testing to attain high first pass yields without retest. Automotive Electronics Council (AEC) guidelines for testing have been developed due rising temperatures under the hood, rising power dissipation of microcontrollers, rising control unit loads, demands for vehicle charging, and higher component integration into smaller packages. One major test requirement is that automotive products require package-level (and wafer-level) testing under three temperature conditions: room (ambient), cold (typically -40C) and hot (typically 150C or higher). As the testing of automotive ICs increases in complexity, it also becomes more time consuming which, in-turn, drives up the overall test time and increases the importance of first pass yield. The key challenge is how to provide thorough test coverage that meets the high-quality requirements of automotive ICs without excessive test costs. During tri-temperature testing, various levels of contamination from the package, pads, solder balls, etc., accumulate within the socket and onto the contactor surfaces. Contactor cleanliness adversely affects socket performance and can impact the first or one pass yields of high value automotive devices. Keeping the sockets clean during package-level testing is critical when meeting quality requirements and long-term reliability. Generally, whenever yield-fallout and/or binout specification limits are exceeded, testing operations are paused to facilitate some level of unscheduled cleaning execution. Unscheduled reactive manual cleaning (i.e., cleaning after the yield drops and/or binouts increase) is time intensive and results in variable yields as well as reduced throughput. Proactive manual cleaning (i.e., cleaning at some predetermined interval before the yield drops and/or binouts increase) results in increased test time reduced overall throughput; however, different devices can have varying thresholds at high and low temperatures. Optimized automated / scheduled contactor cleaning (ACC) using handler functions provides fast proactive and effective cleaning execution. It’s A Dirty Challenge - Experience has shown that over 70% of device yield fallout and re-screen can be attributed to electrical contact issues related to some type of contamination. Keeping the sockets clean during testing is critical when meeting the highest levels of quality requirements and long-term reliability. Practically all roadmap handlers built within the past five years implement some type of automated contactor cleaning (ACC) process using on-board functions and hardware for minimal idle time. Unlike basic manual cleaning operations, the ACC functions can be performed throughout the device testing process without idle time, at temperature without cooling or heating the chamber, and on-demand to maintain the possible highest throughput. Test Contactor Cleaning Device - For maintaining high first pass yields and maximizing test-socket performance, ITS has developed the Test Contactor Cleaning (TCC) devices which are designed to remove debris and contamination from the test sockets and contactor elements. Test Contactor Cleaning (TCC) Devices are ‘turn-key’ surrogate packages fabricated to match the XYZ dimensions of the package and emulate the device package type (ball grid array [BGA], package on package [PoP], quad-flat no-leads [QFN], quad-flat package [QFP], leaded, leadless, etc.). Two basic types of cleaning materials are available for on-line cleaning socket cleaning applications. The cleaning materials are (1) abrasive-polymer-based materials; or (2) tacky-abrasive-materials. Both material types are engineered to collect debris from the pin contact area, remove debris accumulated within the bed of the socket, and polish the contactor surface to recover electrical performance. Using a pre-programmed cleaning recipe, cleaning devices are regularly cycled through a handler with minimal downtime. Depending on the application requirements, the cleaning efficiency of these materials can be optimized across a wide temperature range. Process Improvement for Tri-temperature Device Testing - For this presentation, we will discuss a collaborative project with an end-user that was initiated to investigate the benefits of auto-contactor-cleaning for a high-volume automotive device tri-temperature testing application. For this project, off-line characterization was performed to provide insight into contactor and cleaning material interactions. Device touchdowns, material accumulation on the tip, and cleaning performance were assessed using high magnification, high speed video synchronized to cleaning material interactions, contact resistance performance, and probe force load. Starting with this off-line methodology, the cleaning efficiency was defined and helped to guide the development of optimized on-line cleaning ‘recipes’ in an HVM test environment. Production test cells were selected, each with high throughputs of approximately 750K to one million devices per month. Implementation of cleaning units used for in-situ cleaning execution and the resulting electrical performance was assessed under ambient (T = 25C), cold (T = -35C) and hot (T = +150C) conditions. This successful customer implementation highlights the benefits of this approach within a high-volume testing environment with an emphasis on the overall performance for the long-term cleaning effects and reduced total test time. Summary - Reliable package-level testing is critical for meeting the requirements for known-good-die, known-not-bad die, and ‘zero-defect’ manufacturing without cost of test escalation. Advanced processes, tooling, and practices are necessary to meet these industry and consumer expectations. To maintain yields and consistently attain high data integrity, regular socket cleaning is needed. Programmed preventative cleaning using the handler automation for ‘on-demand’ cleaning execution dramatically improves test cell OEE. These process improvements enable higher UPH metrics and reduce the need for additional test hardware. Small improvements in these key metrics will have immediate benefits for net revenue and lowered cost of test.