Probe Card Lateral Force Balancing via Variable Stiffness
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Solution Overview
Problem
The increasing number of probes on semiconductor probe cards results in significant net lateral forces, compromising testing efficacy and potentially damaging the DUT, as existing solutions like orthogonal probe orientation and increased rigidity are inadequate and costly.
Innovation Solution
The solution involves manipulating the direction and stiffness of individual probes to counterbalance the lateral forces, allowing for a zero or near-zero net lateral force across the probe card, achieved by varying the orientation and stiffness of probes within a single die probe area, which can be scaled up for multiple die testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of probes on the probe card is increased to test more die simultaneously, then the productivity is improved, but the net lateral force increases significantly causing harm to the DUT
Solution Approach 1:
The patent applies counterweight by introducing probes with opposite orientations to counterbalance the lateral forces. Specifically, probes are oriented in multiple directions (e.g., some pointing left, some pointing right) so that the lateral forces from probes on one side of the die are counteracted by probes on the opposite side, resulting in a net lateral force of zero or near zero.
Solution Approach 2:
The patent employs asymmetry by deliberately creating an asymmetric probe configuration where the number and orientation of probes are not uniformly distributed. By having different numbers of probes in different orientations (e.g., more probes pointing left than right, but compensated by probes on the opposite side), the lateral forces are balanced through asymmetric design rather than symmetric uniform distribution.
2Object-affected harmful factors
If orthogonal probe orientation is used to reduce lateral force, then the net lateral force is reduced, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies local quality by making different probes have different orientations and stiffness characteristics tailored to their specific positions and force contribution. Rather than using a uniform orthogonal configuration, each probe is locally optimized with its orientation and stiffness adjusted to contribute to balancing the overall lateral force, creating a non-uniform but balanced force distribution.
Solution Approach 2:
The patent utilizes parameter changes by varying the orientation and stiffness parameters of individual probes to achieve force balance. The stiffness of probes is adjusted (through spring element dimensions or material properties) and their orientations are modified so that the vector sum of lateral forces equals zero, allowing for precise control over the force distribution without requiring complex orthogonal structures.
3Strength
If increased rigidity is applied to the probe card to withstand lateral force, then the structural strength is improved, but the cost and complexity increase
Solution Approach 1:
The patent converts the harmful lateral forces into a beneficial design constraint by using the force balancing principle. Instead of designing a rigid structure to withstand lateral forces, the probe configuration is designed so that the lateral forces cancel each other out, transforming the problem from a structural strength issue to a force balance issue, thereby avoiding the need for expensive rigid support structures.
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 approach ensures uniform scrub marks and reduces stress on the DUT, maintaining testing efficiency while preventing damage, by eliminating the net lateral force, thus enhancing the reliability and cost-effectiveness of the probe card.
Implementation Method 1
the probe may comprise a substrate (1505), probe base (1510), spring element (1515), tip supporting structure (1520), and a probe tip (1525). When the probe card is brought in contact with the die, the Z-direction bending (shown as arrow 1530) allows for an electrical contact between the probe tip (1525) and the contact pad of the DUT.
Data Source
AI summary
A novel method and structure for counter-balancing a lateral force exerted by a probe card onto a device under test (“DUT”) is disclosed. Many DUTs (particularly memory devices) are tested in parallel (i.e., many die at a time) and have unequal numbers of contact pads on top vs. bottom and/or right vs. left sides of the die. The probe card used to test the DUT would necessarily have an uneven distribution of probes that match the contact pads and, as a consequence, may exert a net lateral force on the DUT. By manipulating the individual characteristics of the individual probes, a probe card may be constructed that zeroes the lateral force. Characteristics such as the direction and stiffness of the individual probes can be varied to zero the net lateral force.