QFPCB’s ATE PCB board technology is at the forefront of the industry, leveraging large-scale production capacity, deeply customized equipment, self-developed process parameters, and comprehensive, rigorous testing to overcome the challenges presented by the “Four Highs and One Small”, high layer count, high aspect ratio, high flatness, high reliability, and small pitch. This enables us to effectively support the core competitiveness of fast delivery within two weeks for the full range of ATE PCB boards (Probe Card, Load Board, and Burn-in Board).
ATE PCB Test Board
ATE PCB Test Board, short for Automated Test Equipment, is a device used for the automated testing of the functionality and performance of semiconductor wafers and chips after they are packaged. ATE PCB includes various types of test boards such as Probe Cards, Load Boards, and Burn-in Boards, each serving different purposes such as preliminary screening of unpackaged devices, functionality testing, performance testing, fault detection, and reliability testing after packaging, as well as burn-in testing for packaged chips.
As shown in the figure above, different types of ATE testers require different ATE PCB Boards.
What is ATE PCB Testing?
ATE PCB Testing (Automated Test Equipment Testing) is the process of testing the functionality, performance, quality, and other aspects of integrated circuits (ICs) using automated equipment. It allows for efficient and precise testing of large volumes of chips on the production line, helping to identify manufacturing defects, ensuring the products meet design specifications, and preventing defective chips from entering the market.
ATE PCB testing includes testing various parameters of the chip, such as DC parameters, AC parameters, and functional tests, to evaluate the chip’s performance, functionality, and reliability. These tests ensure that the chip operates within the specified limits under different conditions and performs its intended tasks effectively. By thoroughly assessing both electrical characteristics and functional operations, ATE PCB testing helps identify any defects or issues early in the manufacturing process, ensuring the final product meets the required standards.
- DC Parameter Testing: This involves steady-state tests of device parameters, such as contact resistance testing, leakage current testing, threshold voltage testing, output voltage testing, and power consumption testing. These tests help assess the chip’s basic electrical characteristics and ensure that it operates within the required specifications under static conditions.
- AC Parameter Testing: This validates time-related parameters, such as operating frequency and the relationship between input and output signals over time. Common measurements include rise and fall times, propagation delay, setup and hold times, and storage times. These tests are crucial for evaluating the chip’s dynamic performance and ensuring its proper functioning in high-speed applications.
- Functional Testing: This simulates the IC’s actual operating conditions by inputting a series of ordered or random test patterns. The output signals are then checked to see if they match the expected pattern data. This helps determine whether the circuit’s functionality is working as intended, ensuring that the chip performs its intended tasks correctly.
ATE PCB (Automated Test Equipment) utilizes four main types of test boards, each corresponding to different testing stages: Probe Cards and Interposers (MLO) are used for wafer testing machines to connect the wafer with the testing equipment; Load Boards are used in FT (Final Test) machines for functional and performance testing of packaged chips; and Burn-in Boards (BIB) are used in burn-in test machines to verify chip reliability under extreme conditions over extended periods. These test boards play critical roles in their respective stages, ensuring chip quality meets the required standards.
Probe Card PCB
During the wafer stage, the testing process is referred to as Chip Probing (CP) testing, which requires the use of a critical piece of equipment called a probe card. A probe card is a multilayer printed circuit board (Probe Card PCB) filled with various test channels designed to connect the wafer to the tester. Before chip packaging, engineers must verify the functionality of each chip to ensure that only qualified chips proceed to the next packaging step.
Given the tiny size of the chips, the probes on the probe card act as precision “probes” that make contact with the wafer’s pads or bumps, transmitting test signals to the Automated Test Equipment (ATE PCB). This helps evaluate the chip’s electrical performance.
Probe cards PCBs Board can be categorized based on the type of probes used, including cantilever probe cards (also called epoxy probe cards, where probes are fixed with epoxy resin), vertical probe cards, Blade Probe Card and MEMS probe cards. Among these, cantilever probe cards are the most commonly used due to their low cost, abundant reference materials, standardized designs, and relative ease of customization, making them suitable for scenarios with low signal requirements.
Cantilever Probe Card
The Cantilever Probe Card features probes that extend in a cantilever-like manner to make contact with the wafer surface. This type of probe card is relatively low-cost, with thicker probes, making it suitable for traditional analog chips, logic chips, and other devices requiring larger pads or bumps. However, due to the larger probe diameter, the contact marks left by the probes are deeper, which can result in damage to the wafer pads after repeated contacts.
Vertical Probe Card
The Vertical Probe Card features vertically arranged probes that make direct perpendicular contact with the wafer surface. This structure allows for a higher pin count, making it suitable for high-end chips with smaller pads or bumps, such as mobile processors and GPUs. The contact marks left by this type of probe card are shallower, making it ideal for repeated testing. Additionally, the spacing between probes can be extremely small, enabling precise contact for densely packed designs.
Blade Probe Card
The Blade Probe Card is a widely used high-precision testing device in the semiconductor testing industry, playing a crucial role in the wafer testing stage. It is named for its unique blade-shaped probe design, which features densely packed probes on a metal blade. These probes facilitate the transmission and reception of test signals.
When semiconductor devices are placed on the testing platform, the blade probe card gently presses onto the device, establishing electrical connections with the chip pads or bumps on the wafer. Through this connection, the testing equipment sends test signals to the device and receives response signals, enabling the evaluation of the device’s performance and reliability.
MEMS Probe Cards
MEMS Probe Cards: To enhance throughput and develop probe card technologies with finer pitch and higher pin counts, Micro-Electrical-Mechanical Systems (MEMS) technology has emerged. MEMS probe cards overcome the limitations of traditional manual assembly in epoxy ring probe cards and the individual soldering of micro-spring probe cards. With a high degree of automation, MEMS probe cards board break the cost barrier where manufacturing costs scale with pin count, making them ideal for high-pin-count (~30,000 pins per card), high-current, and large compression stroke testing requirements.
MEMS probe cards printed circuit board ensure exceptional stability and minimal test damage, producing extremely low levels of scratches during testing. They meet advanced testing demands, including fine pitch, flexible test ranges, high pin counts, and high-density configurations. Additionally, they enable simultaneous full-wafer testing, reducing repeated testing damage to wafers, indirectly improving yield rates.
Today, MEMS probe cards PCB are widely used in the most advanced wafer testing fields globally, such as for cutting-edge 7nm and 5nm high-performance processors and GPU chips.
Interposer Board
The BGA pitch on probe cards typically ranges from 85 to 200μm, with high-end products falling between 40 to 55μm. When fine lines are close to the IC Substrate and the line width exceeds the PCB manufacturing capabilities, it becomes necessary to use IC packaging substrate processes such as MLO (Microwave Laminated Organic) or MLC (Microwave Laminate Composite) interposers. These interposers are used to facilitate the signal routing and connection between the probe card and the device under test, enabling effective testing despite the fine pitch and advanced packaging requirements.
The signal in a probe card Board is transmitted through the interposer Board(MLO/MLC interposer board), which acts as a conversion layer, allowing the probes in the probe head to receive the signals. The interposer provides dense routing layers, ensuring that the signals are quickly and efficiently transmitted between components to the testing equipment for analysis. In high-performance electronic devices, the reduced distance between components and the need for high-speed signal transmission can make direct connections challenging. The use of an interposer board helps solve this issue by providing an effective interface for signal routing and ensuring reliable performance in testing scenarios.
Load Board
The Load Board is a mechanical and circuit interface that connects test equipment with the device under test (DUT), incorporating components such as pin sockets, test points, and power interfaces. Primarily used in Final Test equipment, Load Boards facilitate functional and performance yield testing of semiconductor ICs after packaging, assessing parameters like current, voltage, and power. Through rigorous testing at this stage, defective ICs can be identified, preventing failures in downstream electronic products due to chip defects. Load Boards are categorized based on testing platforms, including the 93K series, T2000 series, TUF series, and others.
Load Board designs are often customized to meet the specific testing requirements of different chips, Load Board integrates essential circuits and components, such as resistors and capacitors, to regulate and distribute test signals and power, effectively simulating the electrical conditions of the chip’s actual operating environment.Their durability and reliability are essential for maintaining repeatability and long-term stability in testing processes.
IC Socket
IC Socketis an inline connector specifically designed to meet the testing needs of a particular chip. It serves as a static connector between the IC and the Load Board PCBs, enabling easier replacement and testing of chips without the need for continuous soldering and desoldering.
By eliminating the need for direct soldering, the IC socket prevents damage to both the chip and the Load Boards PCB during the testing process. This design ensures efficient and quick testing, making it an indispensable component in chip evaluation and production workflows.
In production lines, Load Boards are often used in combination with IC Sockets. The IC Socket acts as a temporary fixture, securely holding the chip in place, while the Load Board establishes electrical connections. This pairing allows chips to undergo multiple tests without sustaining damage, helping to identify and filter out defective units and ensuring the final product meets quality standards.
Burn-in Board
Burn-in Board (BIB) is a type of test board used to assess the reliability and performance of semiconductor devices under stress conditions. It is typically used in the burn-in testing phase, where chips are subjected to prolonged operation at elevated temperatures, voltages, or other extreme conditions to detect potential defects or weaknesses before they are shipped. Burn-in testing helps to identify early failures, ensuring that only fully functional and reliable chips proceed to final assembly and distribution.
The Burn-in Board provides the necessary connections for power, ground, and test signals, and it is designed to handle the high current and heat generated during the burn-in process. The BIB typically includes sockets or fixtures for inserting the devices under test (DUT), and it may have specialized circuitry for controlling and monitoring the test environment. Burn-in Boards are essential in ensuring the quality and reliability of semiconductor devices, especially in high-performance and mission-critical applications.
Since burn-in testing requires prolonged exposure to high-temperature environments, the PCB material used for burn-in boards must possess excellent reliability and durability to withstand the stress of extended and repeated high-temperature conditions.
Burn in Test
HTOL (High-Temperature Operating Life Test) testing is primarily designed to simulate the continuous operation of ICs in high-temperature environments, with applied voltage or current, to assess whether the IC’s functionality and characteristics are affected by extreme conditions such as high temperatures (typically 125°C or higher) and high voltages. The test is used to evaluate the long-term operational life of the IC. The burn-in period is typically 1,000 hours, with functional re-testing conducted at intervals, usually after 168 hours and 500 hours, to check for any degradation or failures. This testing helps predict the reliability and longevity of the IC under harsh operating conditions.
LTOL (Low Temperature Operating Life Test) is a low-temperature life test primarily aimed at simulating the behavior of ICs in environments ranging from -55°C to 0°C. The test typically lasts for 1,000 hours and is designed to accelerate the diffusion of moisture through external protective materials and metal wire interfaces, penetrating to the inside of the device. This helps evaluate the IC’s resistance to moisture.
As the injection effect of hot carriers is more pronounced at low temperatures, LTOL testing is particularly important for specific types of devices, such as memory devices or sub-micron size components, where moisture resistance and low-temperature behavior are critical for ensuring long-term reliability and performance.
Burn in Board Materials
Burn-in boards are designed with materials tailored to the temperature and performance requirements of the testing process. For testing up to 125°C, a special version of FR4, known as High Tg FR4, is commonly used. For higher temperatures, up to 250°C, Polyimide materials like VT-901, 85N, and SH260 are preferred due to their excellent heat resistance.
In applications where exceptional heat resistance and mechanical strength are crucial, ceramic materials（RO4350B,WL-CT350,S7136H） are used, offering high thermal conductivity to manage the elevated temperatures during burn-in tests. However, ceramics tend to be more expensive and harder to process. The selection of materials for burn-in boards must balance factors such as thermal management, electrical integrity, cost, and performance to ensure reliable testing and component performance.
ATE PCB Load Board Design
Creating a load board is a process that includes design, layout, fabrication, assembly and test, and possibly multiple redesigns. Engineers must take into account the fact that all of the dc power supply, digital control, mixed signal, and RF signal lines must coexist and be routed among each other on a common board. This inevitably requires a multilayered load board to be fabricated.
As a test engineer, you must create the design specification that a PCB vendor can use to lay out and manufacture a load board. The complexity of the design will mirror the performance requirements of the DUT—high-speed mixed-signal chips require a much more complex load board than do low-speed digital chips.
Load-board design is a critical part of any project that uses ATE to test integrated circuits. Load boards provide the interface between the ATE and the device under test (DUT). A properly designed load board allows full test and measurement of the DUT without distorting the DUT’s performance. An improperly designed load board may limit the types of tests that can be run, diminish the quality of testing, or in the worst case, prevent the DUT from being tested at all.
One of the most important components on the load board is the DUT socket. Its selection is critical to the overall performance of the load board and ultimately the test system. There are many different types of sockets from different manufacturers and selection will depend on several factors like: package type, frequency of operation, cost, contact type, contact material, DUT power requirements, temperature of operation, etc.
The choice of materials for load boards is evolving to meet the industry’s changing requirements. Advanced materials, such as high-frequency laminates and exotic alloys, are employed to enhance the load board’s electrical performance, mechanical strength, and thermal characteristics.
When it comes to high speed digital devices the ideal characteristic impedance for the load board should be 50 ohms. When laying out the high speed signal traces maintaining 50 ohm impedance will increase the bandwidth of the signals and prevent mismatching. A practical rule to remember is that it takes about an inch of trace for every nanosecond of signal rise time, so for a 2 nanosecond rise time signal a trace greater than 2 inches must be considered to be a transmission line and should be treated as controlled impedance trace.
The high-performance signals deserve first priority for your load-board design. You should route them to high-performance instrumentation within the test head or to a connector on the load board, where they will be accessible via cable to any instrument. Keep the trace lengths for high-speed signals as short as possible. Avoid long parallel runs of mixed types of signals to reduce noise coupling. If the signals are differential pairs, then route them in pairs with matched lengths. Expect ±5ps tolerance for matched-length traces. Route the high-performance signals on their own signal planes, separate from the low-speed digital signal planes.
During lay out of a mixed signal load board any component, including buffers, op amps, analog power supply pins that are part of the analog portion of the DUT should be connected to the analog supply power plane. Any digital supply pin and any digital circuit or components should be connected to the digital supply power plane; do not mix components from the two different power planes. The digital output pins generate fast current transients every time their outputs toggle creating noise that couples to the power lane, you want to keep these transient away from the analog power supply plane and prevent the injecting noise into the analog circuitry.
Pins that will connect to a cable require that a connector be mounted on the load board. High-speed applications commonly use SMA and SSMB connectors. SMA connectors are screw-on/off and are larger and have higher bandwidth than the push-pull SSMB connectors. SMA connectors also provide a sturdier connection to the load board. The SSMB connection can be bent by the weight and pull of heavy semi-rigid cables.
ATE PCB Board Manufacturing and Production
high alignment precision and high aspect ratio
The manufacturing of Load Boards requires high alignment precision and high aspect ratio. Typically, these boards have more than 30 layers, with BGA pitch controlled between 30 to 50 mils, and support 4 sites、8 sites，and 16 sites parallel test channels. During production, the alignment offset between layers must be less than 20μm, and the drilling precision must ensure that the distance to the conductor is less than 4 mils. These strict requirements pose greater technical challenges for layer-to-layer alignment, drilling precision, and the copper plating and resin-filled hole processes under high aspect ratio conditions. This demands precise process control and high-precision equipment to ensure the Load Board operates stably and efficiently in multi-channel parallel testing.
80-layer ATE PCB test board
In addition, high aspect ratio is a significant challenge, particularly when the through-hole aspect ratio reaches 40:1, and the smallest hole depth for micro-hole drilling is 0.13mm, requiring extremely high drilling precision. The ate pcb board thickness far exceeds the length of the drill bit, making it impossible to drill through in a single pass. Therefore, a three-step drilling process is employed to complete deep micro-hole drilling. The electroplating copper in the holes must exceed 18 microns, Pulsed electroplating is used to successfully achieve a minimum copper thickness of over 21 microns in the micro-holes.
High flatness
Probe cards and high-end ATE PCBs have very stringent requirements for flatness. The warpage rate should be controlled within 0.1% to 0.2%. The height variation of the pads in the BGA (Ball Grid Array) area should be kept within 50µm (2 mils), and in more stringent cases, the variation should be maintained within a range of 25–28µm (1 mil). These tight requirements ensure reliable performance and precise contact between the probe head and the board during testing.
Signal Integrity
High-end ATE PCB boards require a specified impedance tolerance of ±5%, and the stub length of the back-drilled vias must be kept below 5 to 8 mils. Due to the strict impedance requirements, the quality control of plating, etching uniformity, and the back-drilling process are all critical factors. Ensuring these processes are performed with high precision is essential to maintaining signal integrity and minimizing transmission loss or reflections, which could otherwise negatively impact the performance of the test equipment.
Appearance Quality
Since the DUT (Device Under Test) area on ATE PCB boards establishes connections with probes via pads, the probe card requires that the pads be free from any indentations or damage. Additionally, the gold surface of the pads must be free from scratches or roughness. Any defects in the pads can lead to poor contact or signal integrity issues during testing, making the aesthetic and functional quality of the pads crucial for reliable performance.
QFPCB Factories have extensive experience in the manufacturing of complex ATE PCB boards, such as handling high aspect ratio drilling, pulsed plating for hole copper deposition, controlling flatness for DUT pads and PCB, achieving high layer-to-layer alignment accuracy (<0.002”), and implementing ENCAP processes and through-hole bonding techniques.
Given that ATE PCB boards are typically produced in small batches but require rapid delivery, QFPCB has developed an efficient delivery process. This includes pre-manufacturing DFM communication, engineering production, material preparation, dedicated production lines during manufacturing, and after-sales services, all designed to meet the tight timelines of chip R&D and design cycles.