Motor Torque Limiting in Semiconductor Probe Testing
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Solution Overview
Problem
High-density semiconductor devices with small hemispherical solder bumps pose challenges for probe cards, leading to excessive torque and motor overload during electrical characteristic measurement due to fine misalignment and thermal expansion, causing the probe card to move and apply significant load on the motor.
Innovation Solution
A device test method that limits the maximum torque generated by the motor to a predetermined value, allowing the stage to move and reduce the load on the motor, by adjusting the moving force and using a probe card with protuberant engagement parts to engage with solder bumps, ensuring the motor load remains within a safe limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-density solder bumps are used to increase integration degree, then the number of electrodes increases, but it becomes difficult to arrange probe needles at high density
Solution Approach 1:
The probe needle array is divided into multiple independent probe cards, each handling a subset of solder bumps. This segmentation allows each probe card to maintain manageable density while collectively testing all electrodes of the high-density device.
Solution Approach 2:
The system transitions from a single-plane probe needle arrangement to a multi-layer configuration where multiple probe cards are stacked vertically, each card testing different regions or layers of the device, thereby increasing effective testing capacity without increasing horizontal density.
2Reliability
If the probe card is made rigid to maintain contact, then measurement stability improves, but thermal expansion causes the probe card to move and overload the motor
Solution Approach 1:
The probe card is designed with controlled flexibility, allowing it to expand and contract with thermal changes while maintaining contact with solder bumps. This dynamic adaptation prevents rigid thermal expansion forces from being transmitted to the motor system.
Solution Approach 2:
The mechanical properties of the probe card are modified by changing material composition or structural parameters to achieve optimal flexibility, allowing thermal expansion without generating excessive force that would overload the motor.
3Measurement precision
If the motor generates high torque to prevent stage movement, then measurement precision improves, but the motor may be overloaded and damaged
Solution Approach 1:
A torque limiting mechanism is built into the motor drive system that prevents torque from exceeding a safe threshold. This cushioning protection is activated before overload conditions can damage the motor, ensuring both measurement precision and motor safety.
Solution Approach 2:
The motor control system incorporates feedback from torque sensors or current monitoring that detects approaching torque limits and adjusts motor output accordingly, maintaining measurement stability while preventing motor overload through real-time control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively limits motor load, preventing overload and maintaining contact between probe electrodes and solder bumps, even during thermal expansion, thereby ensuring accurate measurement without damaging the motor.
Implementation Method 1
a linear motor, and by moving the stage, each probe needle 110 of the probe card 111 is positioned to correspond to each electrode pad 120
Implementation Method 2
the probe card 111 may be thermally expanded by the heat generated by current flow while the electrical characteristic of the semiconductor device is measured
Data Source
AI summary
A device test method performed in a substrate test apparatus which includes a mounting table for mounting thereon a substrate on which a device having an electrode is formed, the mounting table being movable by a X-direction motor and a Y-direction motor, and a probe card arranged to face the mounting table. A measuring electrode is arranged to correspond to the electrode of the device, the probe card has a probe that is engageable with the measuring electrode, and the X-direction motor or Y-direction motor generates torque to keep the mounting table from moving when measuring an electrical characteristic of the device. In the device test method, after the probe is engaged with the measuring electrode, when measuring an electrical characteristic of the device, the maximum value of the torque generated by the X-direction motor or Y-direction motor is limited to a predetermined value or less.