Metallization: Making Conductive Traces on Silicon Chips.

Summary

In this video, the creator explores an innovative, low-cost method for creating conductive metal traces on silicon chips using photolithography and a silver mirror reaction. By overcoming several technical challenges—such as poor adhesion and the risk of damage during the process—the creator develops a successful technique for depositing silver using basic chemicals. The result is a functioning metalized circuit with acceptable conductivity, though improvements are needed for better durability and precision. The video showcases creative problem-solving and emphasizes the potential of low-tech solutions in electronics fabrication.

Takeaways

• 😀 The process of metallizing chips with silver involves using a thin layer of photoresist and a laminator, but issues arise due to poor adhesion between the photoresist and silver layer.
• 😀 Silver is a highly conductive metal, but its adhesion to chips can be challenging. Manufacturers typically deposit silver on another layer for better adhesion to materials like glass.
• 😀 A major issue is the delamination of the silver layer, which occurs because the plastic layer on the photoresist sticks better than the silver does to the chip.
• 😀 The speaker considers replacing the clear plastic layer with PTFE (Teflon) tape, a highly slippery material, to help prevent delamination during processing.
• 😀 Teflon tape is used to separate the plastic layer from the photoresist, allowing for better manipulation of the fragile resist layer while keeping the silver intact.
• 😀 Adjusting the laminator's temperature can help avoid damaging the resist or forming bubbles during the process, ensuring a cleaner result.
• 😀 After exposing and developing the photoresist, silver etching is performed, leaving behind well-defined metal traces on the chip.
• 😀 Once the silver layer is etched away, the photoresist is removed using acetone, which successfully separates the photoresist without affecting the silver traces.
• 😀 Conductivity tests of the traces reveal acceptable resistance values, though the speaker acknowledges potential for improvement in the silver layer thickness for better conductivity.
• 😀 To address durability issues with the silver layer, conductive paint is used to protect the landing pads from abrasion, although it's not a perfect solution.
• 😀 The process is tested for resolution, and the speaker finds that the metal layer resolution is primarily limited by the photolithography, achieving satisfactory results in the end.

Q & A

What was the main challenge faced in the metalization process described in the video?

The main challenge was that the silver layer was not adhering properly to the photoresist layer, as the plastic protective layer adhered better to the photoresist than the silver. This caused the silver layer to delaminate during processing.

How did the speaker resolve the issue with adhesion between the silver layer and the photoresist?

The speaker replaced the plastic protective layer with PTFE (Teflon) tape, which is highly slippery and would allow the photoresist to separate from the silver layer without damaging it.

What role did the laminator play in the process, and how was it adjusted?

The laminator was used to apply heat and pressure, helping to bond the photoresist and silver layers together. The temperature was adjusted slightly lower to avoid damaging the resist and to prevent bubbles from forming.

Why is PTFE (Teflon) tape specifically chosen for this process?

PTFE tape was chosen because of its slippery nature due to carbon-fluorine bonds, which allowed for easy separation of the photoresist without pulling off the silver layer.

What method was used to remove the unwanted silver after it was deposited?

A silver etching solution was used to remove the unwanted silver, leaving only the desired conductive traces.

What was the outcome after the silver etching process was completed?

The silver etching process was successful, leaving clear and precise conductive traces, and the photoresist layer was removed using acetone without damaging the silver.

What were the resistance values of the different traces measured by the speaker?

The narrow trace had a resistance of about 20 ohms, the medium trace had 10 ohms, and the fat trace had 5 ohms, which were considered acceptable for the project.

What issue did the speaker encounter with the durability of the silver layer, and how was it addressed?

The speaker encountered durability issues with the silver layer, especially when probes scraped the landing pads. To protect the pads, the speaker manually applied conductive paint, although the result was not perfect.

What future improvement did the speaker consider for enhancing the protection of the silver layer?

The speaker considered using conductive epoxy in the future, which might offer better protection for the silver layer compared to the conductive paint used.

What did the speaker find when testing the resolution of the metalization process?

The speaker found that the resolution of the metal traces was good, with minimal undercutting, and attributed the resolution limitation to the photoresist process itself.

What was the speaker’s overall assessment of the process after completing the tests?

The speaker was pleased with the results despite facing multiple challenges. They were satisfied with the silvering process but acknowledged that further improvements could be made, such as creating a thermal evaporator for increased flexibility.

How did the speaker express gratitude to those who supported the project?

The speaker thanked everyone who watched the video and especially those who provided support via email and patrons who funded the project, allowing them to purchase necessary chemicals and materials.