Saturday, September 25, 2021

Underwater laser cutting and silver sintering to make ceramic circuit boards

 

Thermal stress cracking can be completely avoided by CO2 laser cutting thin alumina sheets underwater.  I also show how to formulate and apply silver paste, then sinter in a kiln to produce double-sided ceramic printed circuit boards with conductive vias.

60W CW CO2 laser at 80% power.  10mm/sec.  Standard lens focal length (50mm).  2mm water above ceramic.  180 passes to cut through 0.75mm thick alumina.  

Silver paste: 97% silver powder, 3% glass powder by mass.  Particle size 1 micron or less. Add poly vinyl alcohol mold release until desired consistency reached.

Paste applied with 4 mil thick vinyl stencil.  Dried in air 10 minutes, then rapidly brought up to 900*C, held for 10 minutes, then rapidly brought back down to room temperature.  Total cycle about 45 minutes.

I measured electrical conductivity of the finished traces from my process with vinyl stencils: 4 milliohms per square at 10 micron final thickness.  This is pretty close to the Dupont published spec ( less than 2 milliohm/sq at 16 micron thick)

Underwater CO2 laser cutting reference: https://sci-hub.se/10.1016/J.JEURCERAMSOC.2011.06.015
Raspberry Pi picoReflow oven controller: https://apollo.open-resource.org/mission:resources:picoreflow

Applied Science on Patreon: https://www.patreon.com/AppliedScience

Saturday, July 31, 2021

Atomic Layer Deposition of copper - If you like sputtering, you'll love this!

 



An explanation and demo of atomic layer deposition (ALD) of copper metal on glass.  Precursors are copper(I) chloride and hydrogen, processed in a hot-wall tube quartz tube furnace.


10 torr operating pressure

500 sccm argon sweep/purge gas constantly flowing

75 sccm CuCl argon pulse gas (17 seconds including flow controller lag)

100 sccm H pulse gas (14 seconds including flow controller lag)

7 second purge time between pulses

100mm quartz tube furnace diameter 

415*C deposition temperature

350*C CuCl evaporation temperature

Substrates are mostly borosilicate glass cleaned with RCA clean

The "good" samples shown in the video are about 750 cycles (about 9 hours


Main ref:

https://sci-hub.se/https://doi.org/10.1002/cvde.19970030107

Also helpful:

https://sci-hub.se/https://doi.org/10.1063/1.5087759

https://sci-hub.se/10.1149/2.0261501jss

https://sci-hub.se/https://doi.org/10.1016/0022-0248(92)90191-K


Alicat flow controller manuals (hard to find via website navigation):

https://documents.alicat.com/manuals/DOC-MANUAL-MC.pdf

https://documents.alicat.com/manuals/old/Gas_Flow_Controller_Manual_rev7.pdf

https://documents.alicat.com/Alicat-Serial-Primer.pdf


RCA clean: https://en.wikipedia.org/wiki/RCA_clean


CuCl synthesis: http://wwwchem.uwimona.edu.jm/lab_manuals/c1901exp35.html


Support Applied Science on Patreon: https://www.patreon.com/AppliedScience

Monday, February 22, 2021

Measuring human digestive efficiency vs. a flame

 "200 Calories" on a nutrition label doesn't describe the total flammable caloric content. I explore the differences between digestible and flammable calories using a homemade calorimeter with glass windows.






Pressure sensor:
https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/M5842-000005-10KPG/7592854 Schedule 160 pipe on McMaster: https://www.mcmaster.com/7733K259/ 32 ga nichrome wire: https://www.amazon.com/gp/product/B07DL4DSWD/ Power supply (used for ignition wire): https://www.amazon.com/gp/product/B07SS77N7K/ Keithley 6.5 digit multimeter: https://www.tek.com/tektronix-and-keithley-digital-multimeter/dmm6500 Tek MSO 4 series oscilloscope: https://www.tek.com/oscilloscope/4-series-mso-mixed-signal-oscilloscope Soylent: https://soylent.com/ Support Applied Science on Patreon:
https://www.patreon.com/AppliedScience

Sunday, January 17, 2021

Prototyping with Applied Science: Design and build a bite sensor




Join me in brainstorming and building a bite force sensor that allows paraplegic musicians to smoothly control an expression pedal. This video will include construction tips and tricks, methods, material selection, and a little design philosophy.

Tiny linear potentiometer used in final design: https://www.digikey.com/en/products/detail/bourns-inc/3046L-1-103/3781580 Spring-loaded linear potentiometer: https://www.digikey.com/en/products/detail/tt-electronics-bi/404R10KL1-0/2408603 Sil-Poxy for bonding silicone rubber to itself and other materials: https://www.smooth-on.com/product-line/sil-poxy/ Sorta Clear 40 - Platinum-cure silicone molding: https://www.smooth-on.com/products/sorta-clear-40/ Light-cure 3311 adhesive: https://www.mcmaster.com/1700A253/ (expensive, but this tube will last a long time) Blue lasers on eBay "5mW" *wink* https://www.ebay.com/itm/3-Packs-900Mile-Strong-Laser-Pointer-Pen-Green-Blue-Red-Light-Visible-Beam-Lazer/174479770737 Braided shield, highly flexible, 4-conductor cable: https://www.digikey.com/en/products/detail/tensility-international-corp/30-00218/5270175 Fabric reinforced silicone sheet: https://www.mcmaster.com/8612K51/ Mechanical CAD on github: https://github.com/benkrasnow/BiteSensor Support Applied Science on Patreon: https://www.patreon.com/AppliedScience