contribute.

Yuichi Hirose

My name is Yuichi and I will be working on the probe station this semester

Weekly Update #0&1 (1/13 - 1/26)

Accomplishments

  • I was first assigned to the wire bonder development. I joined the wire bonder tutorial with Joe and Joel to get to know how to use it. I had a discussion with Icey, James, Joe, and Joel, and we decided to prioritize the probe station development and the other parts of IC packaging except DIYing a wire bonder for this semester. I was assigned to the development of a probe station.

  • I had a discussion with Anirud and Joel to understand the current situation of the probe station (what have been finished, what not, and what I am supposed to do this semester). Anirud showed me the current prototype from last semester, which helped my understanding.

  • I looked through the documents and CAD from the last semester to understand the situation more.

  • I created a project proposal.

  • I had a discussion with Anirud, Joe, and Joel again to review my project proposal.

    • We decided to use off-the-shelf XYZ positioners and work on a DIY XYZ positioner develepment only if time allows.

    • Because we are going to use off-the-shelf XYZ positioners, we can also use off-the-shelf probes. We don't have to design and DIY them.

    • The camera can be replaced with a USB camera. Another team is also procuring one, so it might be good to obtain the same one for us. C-mount cameras might be benefitial for easy design and assembly.

    • Vacuum chuck is necessary. Lab already has a vacuum pump. We need to obtain a chuck (the one procured last semester is too large).

    • We would like to automate the Z-axis positioning. We need to attach a motor to the Z-axis of the off-the-shelf positioner.

    • Priority: finishing a working DIY probe station > auto-Z function.

Roadblocks

  • These tasks might already be underway by someone, but I'll write down for record

    • XYZ positioner procurement

    • Probe procurement

    • USB camera procurement

    • Vacuum chuck procurement

  • How to implement auto-Z? (Force sensor? High-res encoder?)

Plans for next week

  • Design of a metallic base which XYZ positioners can be attached with magnet.

Weekly Update #2 (1/27 - 2/2)

Accomplishments

  • I looked up metalic boards which might work as the base. If they work, we don't have to make something like the ones above. https://a.co/d/2TJwnC9 https://a.co/d/78COEFO

  • In order to set the state where the positioners are placed higher than the chip (the probes usually go downward from the positioners), we should either

    I assume the design 2 will cost less and will be much easier to make. I can't find any downsides of this design. So we decided to go with the design 2.

  • Anirud and I decided to procure and try the Amazon $125 XYZ stage instead of the $700 positioner first, refering to this design.

  • I discussed with Anirud about his idea on the auto-Z implementation using a piezo vibration sensor like this. He drilled a hole in the center of the sensor, which is for the vacuum chuck, and it sill worked. He told me that the burrs around the hole can be a problem. I think putting a backup board (sacrificial board) under it when drilling might reduce the burrs. Or we can put a conductive spacer, with a larger hole avoiding the burrs, between the sensor and the chuck.

Roadblocks

  • Camera selection

Plans for next week

  • Design an attachment to put magets to the bottom of the Amazon XYZ stage

  • Design a vacuum chuck

Weekly Update #3 (2/3 - 2/9)

Accomplishments

Roadblocks

  • Camera selection

Plans for next week

  • Create a CAD model of an attachment for the probe holder

  • Design an attachment to put magets to the bottom of the Amazon XYZ stage

  • Design or procure a vacuum chuck

Weekly Update #4 (2/10 - 2/16)

Accomplishments

  • I designed an attachment for the probe holder, a magnetic base for the XYZ stage, and created their CAD models.

  • I looked up and selected a magnet and a magnetic board on Amazon.

  • I checked the lab-made patterning stepper device, which our probe station would have a similar structure to. I found that this design is based on the idea that the micrometer handle of the XYZ stage is rigidly connected to the motor, without something springy such as couplers, while the motor is connected to the stage flexibly using a long, thin 3D-printed beam (the motor axis and the micrometer axis cannot be aligned perfectly, so either of them needs to be flexible). I guess, this is also because, for the patterning stepper we need to attach a motor for every X/Y/Z-axis and there is not so much space for it, so the beam needed to be thin. For the probe staion, we need automate only the Z-axis, so I think I would go with the opposite way (rigidly fix the motor to the stage, and flexibly connect the motor and the micrometer). I anticipate that this contributes to the overall stability of the positioner, because the motor would not wobble in that case (it still needs to slide in 1 DoF along with the micrometer handle).

  • I checked the motor of the patterning stepper. It has 200 steps/rev resolution. If we use the same motor in the full step mode, and directly connect it to the micrometer without speed reduction, then the resolution of our device is 2.5 um. I discussed with Joel and confirmed that this is sufficient resolution for the probe station, because the pad size length and width will both be >100um.

  • I discussed with Anirud and Joel whether our probe station needs proximity sensors like the patterning stepper. Because it does not need absolute positioning, we concluded that the sensors are not necessary.

  • I had a discussion with Anirud and Joel about how to hold a chip on the XY stage. We are planning to use the piezo vibration sensor to detect the touch by the probe needle to the chip, for the auto Z-zero setting function. Also, the surface where a chip is put needs to be conductive for testing purposes. The problem is the piezo sensor is larger than regular chips and its face and back sides are not electrically connected. One idea is, if we use a vacuum chuck, to attach conductive tapes on the piezo sensor avoiding the vacuum suction hole so that the chip is positioned on top of the tape, and the bottom of the chip and the tape are electrically connected. Another idea is to use a double-sided conductive tape, instead of a vacuum chuck. In this case, we should fix the piezo vibration sensor using a regular tape, and attach the double-sided conductive tape on top of the regular tape, so the sensor will not be damaged when we replace the double-sided tape.

  • By checking the patterning stepper, I realized the vacuum chuck can be 3D printed. It doesn't have to be a machined aluminum part.

  • I had a discussion with Anirud and Joel about the camera. A cheap USB microscope like this seems sufficient.

Roadblocks

  • How to hold a chip on the XY stage (details above)

Plan

  • 3D print the attachment for the probe holder and assemble

  • 3D print the magnetic base for the XYZ stage and assemble

  • Procure magnets

  • Design a vacuum chuck / test double-sided conductive tape for holding a chip on the XY stage

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