Probe cards play a crucial role in integrated circuit testing, especially in wafer testing. As the interface between ATE testing machines and semiconductor wafers, probe cards ensure preliminary measurement and screening of their electrical performance before chip packaging.
What is a probe card?
Before chip packaging, engineers need to confirm whether each chip is working properly to ensure that only qualified chips enter the next packaging process. Due to the extremely small size of the chip, the probes on the probe card are like precise "probes" that come into contact with the pads or bumps on the wafer surface, transmitting test signals to ATE (automatic testing equipment) to help determine the electrical performance of the chip.

2. Structure and composition of probe card
The structure of a probe card is similar to a customized circuit board (PCB), which consists of probes and other functional components. The probe is the core component of the probe card, responsible for actual contact with the wafer, while the PCB serves as the carrier, carrying the probe and other components, and achieving signal transmission. According to the testing requirements, the probe card can also include other components, such as stiffeners, to enhance its stability.
Main components: Probe: responsible for contacting the solder pads on the chip surface and transmitting electrical signals to the ATE equipment.
PCB（Printed Circuit Board）： The circuit board is an important component of the probe card, which connects the probe with the testing equipment to ensure the effective transmission of test signals. Stiffener: Improve the mechanical strength of the probe card to avoid inaccurate contact of the probe due to bending during operation or use.
3. Classification of probe cards
According to structure and technology, probe cards can be divided into cantilever probe cards, vertical probe cards MEMS probe card.
The probe of the Cantilever Probe Card extends in a cantilever shape towards the wafer, making contact with the surface of the wafer. This type of probe card has lower cost and relatively thicker probes, and is usually used for traditional analog chips, logic chips, and other chips that require larger solder pads or bumps. However, its probe diameter is large and the needle marks are deep, making the solder pads on the wafer easily damaged after multiple contacts.
Vertical Probe Card probes are arranged vertically and in contact with the wafer surface. This structure can accommodate more pins and is suitable for high-end chips with smaller solder pads or bumps, such as mobile phone processors, GPUs, etc. This type of probe card has shallow needle marks, suitable for repeated testing, and the spacing between probes can be very small.
MEMS Probe Card adopts Micro Electrical Mechanical Systems (MEMS) technology to achieve extremely fine probes, suitable for testing requirements with very small spacing and high needle count. MEMS probe cards have a high degree of automation and consistency, and are commonly used in the most advanced semiconductor processes, such as 7nm and 5nm high-end processors or GPU chips. It is like a "mini surgical knife" with extremely high precision, capable of arranging probes in micrometer sized spaces.
4. Application and Challenges of Probe Cards
As an indispensable device in CP (chip probing) testing, probe cards are mainly used in the wafer testing process to help screen out defective chips before packaging. Each probe card is a customized product for a specific chip and does not have universality. Therefore, although the annual production of a chip may reach millions, the demand for probe cards is usually relatively low.
In practical applications, the design and selection of probe cards have a significant impact on testing accuracy, efficiency, and cost. The lifespan and stability of probes, the quality of contact with wafers, the size of probe traces, and the spacing between probes are all key factors that need to be considered. For example, in high needle count and short needle spacing testing scenarios, vertical probe cards and MEMS probe cards have significant advantages, while for cost sensitive and low testing requirements scenarios, cantilever probe cards are an economical choice.
5. Storage and maintenance of probe cards
The probe card is very precise and requires careful maintenance during use and storage. Probe cards are often vacuum packaged at the factory to avoid the influence of humidity and impurities in the air on the probes. Idle probe cards should be stored in an environment with good humidity control, such as a nitrogen cabinet, maintaining a humidity of around 25% to extend their service life.
6. Future Trends of Probe Cards: The Rise of MEMS Technology
With the continuous advancement of semiconductor technology, the size of chips is getting smaller and the spacing between solder pads is also decreasing. This puts higher demands on the probe card. MEMS probe cards are becoming the mainstream of high-end probe cards in the future due to their extremely thin probe diameter, consistent height, and stability. Unlike traditional cantilever probe cards, MEMS probe cards can support more pins, fine pitch testing, and reduce probe damage to wafers. With 5G AI、 The development of emerging technologies such as the Internet of Things will lead to an increasing demand for MEMS probe cards.
The role of probe cards in integrated circuit testing is crucial. It is not only the interface between ATE and wafer, but also an important tool to ensure chip yield and quality.

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