The working principle of the wafer probe station is to achieve the transmission and measurement of electrical signals by contacting a set of micro probes with the testing points of the chip. These probes are usually made of metal materials and can be positioned with micrometer level accuracy. The structure of the probe station includes a bracket, a mobile platform, probes, and a control system.
Probe Card is a key component in the wafer probe station. The transmission and feedback of test signals are achieved through direct contact between the probe and the solder pads or bumps on the chip.

The main functions of the probe card include:
1. Connect testing equipment to the wafer: As an interface between automatic testing equipment (ATE) and the wafer, it facilitates the testing of individual circuits on the semiconductor wafer.
2. Electrical performance testing: Conduct preliminary measurements of the electrical performance of the chip before packaging to screen out defective chips.
3. Signal transmission: Measuring electrical characteristics such as signal integrity, power, and functionality through fine metal contacts that directly interact with wafer circuits through probes.

The core components of the probe card include:
1. Probe: The probe is the core component of the probe card, responsible for directly contacting the circuits on the wafer and transmitting electrical signals. There are various materials for probes, including tungsten (W), rhenium tungsten (ReW, 3% R 97% W), beryllium copper (BeCu), P7 (P), palladium (Pd), and P8 alloy.
2. Printed Circuit Board (PCB): The PCB serves as the substrate for the probe card, providing circuit connections and structural support. It connects the probe with the testing equipment to ensure effective transmission of test signals.
3. Functional components: may include electronic components for signal conditioning and distribution, as well as other functional components such as stiffeners to enhance their stability.
The types of probe cards mainly include:
1. Cantilever Probe Card:
·Structural features: The probe is cantilevered, similar to a suspension bridge, and can extend towards the wafer and make contact with its surface. The probe materials of the cantilever needle card include tungsten (W), rhenium tungsten (ReW, 3% R 97% W), beryllium copper (BeCu), P7 (P), palladium (Pd), and P8 alloy.
·Advantages: Low cost, suitable for chips with larger solder pads or bumps.
·Limitations: The large diameter of the probe may cause damage to the solder pads on the wafer after multiple contacts.
2. Vertical Probe Card:
·Structural features: The probes are arranged vertically and in vertical contact with the wafer surface, similar to an elevator. Vertical probe cards typically include probes, probe holders, substrates, as well as peripheral interfaces and circuits on the structure. The material of the probe part is usually chosen to have high conductivity and good mechanical properties, such as tungsten, diamond coating, or special alloys.
·Advantages: Able to accommodate more pins, suitable for high-end chips with smaller solder pads or bumps, such as mobile phone processors, GPUs, etc.
·Features: The needle marks are shallow, suitable for repeated testing, and the probe spacing can be very small.
3. MEMS Probe Card:
·Technical features: Adopting microelectromechanical system technology, the probe is extremely precise.
·Advantages: Suitable for testing needs with very small spacing and high needle count, with high automation and consistency.
·Application: Commonly used in the most advanced semiconductor processes, such as 7nm and 5nm high-end processors or GPU chips.
·Features: High precision, able to arrange probes in micrometer level space, similar to a mini surgical knife.
In addition, the selection of probe cards depends on the characteristics of the tested chip, such as the size and spacing of solder pads or bumps, testing requirements (such as current, voltage, frequency, etc.), and cost-effectiveness. In practical applications, selecting the appropriate probe card requires comprehensive consideration of the above factors, as well as specific testing environments and objectives. For example, during the development phase, there may be a preference for using high-precision MEMS probe cards to ensure the accuracy of test data. In large-scale production, more emphasis may be placed on cost-effectiveness and testing efficiency, choosing cantilever probe cards or vertical probe cards.
With the development of semiconductor technology, the design of probe cards is also constantly advancing to meet the testing needs of higher density and smaller chip sizes. MEMS probes, with their high precision and density, are particularly suitable for chip testing at advanced process nodes.

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