Sunday, March 30, 2014

DEPOSITION ACRONYM DEFINITIONS

The various deposition acronyms don't really have solid definitions. For example, depending on who you ask you may get different answers as to what the acronym PVD (physical vapour deposition) means and / or the process it refers to. In Episode 3 of Coaters Tech videos I talked about what these definitions mean and defined them.

The following is a list of those acronyms and their definitions:
  • PVD - physical vapour deposition - The process by which a material is vapourized and deposited where the source material and the deposited material are the same in their chemical makeup. In this process there may be dissociation of compounds at the source but upon deposition the dissociated elements recombine to become the same compound as the source material (eg. MgF2, Au).
  • CVD - chemical vapour deposition - The process by which a material is vapourized and deposited where the source material (either through intent or dissociation) and the deposited material are different in their chemical makeup. In this process the source material or the vapourized components of the source material require process gasses to achieve the desired deposited compound (eg. Ti2O3 > TixOy vapour + O2 = TiO2, HfO2 > HfxOy vapour + O2 = HfO2).
  • PECVD - plasma enhanced chemical vapour deposition - The process by which a deposited materials' physical properties are manipulated during deposition with the bombardment of plasma (accelerated charged particles) (eg. deposited material density).
  • PACVD - plasma activated chemical vapour deposition - The process by which a material is vapourized and deposited where the source material and the deposited material are different in their chemical makeup. In this process the vapourized source material requires charged process gasses to interact with chemically in order to achieve the desired deposited compound (eg. Ti + N+ = TiN). The ionized process gas is required to achieve the desired deposited compound.
PECVD - magnetron sputtering with an ion gun
More acronyms for thin film deposition whose definitions are specifically implied and fall under the 4 definitions listed above are:
  • ALD - atomic layer deposition
  • MOCVD - metal organic chemical vapour deposition
  • MBE - molecular beam epitaxy
  • PLD - pulsed laser deposition
  • ...and many more.
What do you think? How do you define the various deposition acronyms?
What are some other deposition technique acronyms?

Thursday, March 27, 2014

EQUIPMENT FAILURE CAN BE A MISSED OPPORTUNITY

Diffusion pump taken apart for repair.
I was in the lab with students at Niagara College when the diffusion pump gave out (finally) on the coating chamber beside the one we were using. At the school with students it was an excellent opportunity to show them how to take a high vacuum pump off a coating chamber (letting it cool, venting the pump, draining the water etc.) and see inside the pump. Operation of various pumps is part of the curriculum but getting some hands on with them isn't. This group of student will graduate with a little extra experience.

In a production environment a failure like this can prove disastrous. But don't let the same opportunity go to waste with your staff.

Most technicians, engineers and management don't get to see the inside of a pump that often, or at all. Labs usually have one or two people that swoop in and take care of the repair and/or replacement of failed equipment. Some contract that kind of work out to companies like Intlvac. When you have a failure of any kind (diff pump, gauge head, water leak in the chamber...) take a moment or two and gather everyone to get a perspective or view of equipment we normally don't get to see. And when it's failed equipment make sure to point out the failure.

Broken lab and production equipment is one of those things no one wants but at the same time it can be an invaluable opportunity for you and your staff.

P.S. A couple of years ago I found a very small leak in a meissner trap in a Satisloh 1200 DLF. The polycold gas was leaking into the vacuum. After some troubleshooting and realizing what the problem was I was excited. Maybe a little too excited because the GM wasn't pleased with my attitude towards what turned out to be an expensive replacement part. BUT... I got to see what a meissner trap leak looked like while the chamber was trying to pump down to start pressure. I even grabbed a couple of people to come and see.

Tuesday, March 25, 2014

3D PRINTING OF OPHTHALMICS

How long will it be before eyeglass lenses are 3D printed?

About a year ago I visited 3D printer manufacturer Stratasys to investigate the possibility of printing ophthalmic lenses. What I found was the printing process using materials used to print with can't be made transparent. The best that can be done so far is a translucency not suitable for optical applications. Due to the printing process (melting of polymer threads fed onto the printing stage) the printed structure results in a lot of internal scatter.

Here's a good video from Stratasys showing translucent 3D printed parts.



For those readers not familiar, here's a video demonstrating current ophthalmic lens manufacturing. (Skip past the first 30 seconds)



If you compare current ophthalmic lens manufacturing to the 3D printing process its easy to see the savings. The most apparent is material waste. An ophthalmic lens blank comes in standard sizes and then has to be generated, polished and edged to fit in a frame. Depending on the prescription and frame size and shape, the material cut away and discarded may be over 80% of its original blank size.


Other major savings will include equipment, floor space for that equipment, water, power, and waste removal. These savings are more than significant. And depending on the size of the printer labs can print several pair at a time.

Once 3D printing has advanced to the point where transparent parts can be printed it won't be long before full pairs of glasses are printed, frames and all.

Going further still, as the technology progresses glasses can be printed not only with frames but with optical density in a wide range of colours for sunglasses (tints) and possibly with AR coatings. A welcome bonus will be printing lenses in 'tinted' colours will ensure the colour chosen by the customer matches the colour they've actually chosen at the store (I know all too well how frustrating this can be!).

Objet Eden500V 3D printer from Stratasys.com
As far as AR printing is concerned, currently the tolerancing for 3D printing is on the order of ± 16 microns (for the printer pictured at left). To print AR coatings that tolerancing has to come down to ± 1 nanometer.

As I see it the future of ophthalmic lens manufacturing will be a lab with one or more 3D printers connected to the internet taking prescription orders for specific frame styles including tints for sunglasses and fashion.

I am happy to say my job as a coating process specialist is safe for the foreseeable future.

Sunday, March 23, 2014

INTRODUCE YOUR ENGINEERS AND YOUR TECHS TO EACH OTHER

Coating engineers and coating technicians don't typically mingle with each other. This is a detriment to productivity and efficiency. They are on the same team and their goals are the same.
Discussing design and deposition. Photo credit - Niagara College Canada

Most coating engineers are university graduates with Masters and PhD's. With an intimate understanding of physics, wave theory and quantum electrodynamics, engineers bring high value to any company designing coatings that make optical devices work. When it comes down to it, without coatings optical devices would be useless. But with little experience actually depositing thin films using your equipment in your lab, it's essential that engineers spend time in your lab.

Most coating technicians start working in your lab with no thin film experience at all. It's always a struggle to hire a new coating technician.

Usually a new coating technician is new to the technology, or at least new to your equipment. There's a steep learning curve during their training. It's inevitable that new techs learn the hard way - by making mistakes (I know I did). Only with the passing of time and that hard earned experience do techs become familiar with equipment and materials that may be new to them. And which processes do what for your products.

With the above two statements being the common truth you can minimize mistakes and inefficiencies by introducing your engineers to your technicians. Engineers should talk to techs about the equipment they use and techs should find out how and why a particular coating design is being implemented.

If engineers are familiar with your coating chambers and their individual "personalities" (see the Chamber Characterization post) they will become more efficient designers by knowing what is and isn't practically possible before they start. Have your engineers spend time in the lab learning from your technicians. After all, it's usually the engineers that require the characterization data and the techs doing the characterization.

If techs have a better understanding of the coatings they are asked to deposit they will be aware of what to look for while operating the coating machines they've become so familiar with. They will become better trouble shooters. They will produce more efficiently. Make sure your techs know how sensitive a design may be and which layers may be the cause of a performance failure. They'll set up the chamber and materials and monitor the deposition process with these details in mind.

Bring your entire team together. When you have meetings make sure your engineers and your technicians are side by side and have a complete understanding of the product goals. Eliminate that all too common gap that exists in your team. Get your engineers and techs talking to each other more often.

Friday, March 21, 2014

A GOOD EXAMPLE OF UNCONVENTIONAL THIN FILM PROCESS DEVELOPMENT AND ENGINEERING

A really good example of thin films process development resulting on NOT fighting environmental effects in application of the product. Most of the time we design and develop thin films to resist the environment (denser films, boundary layers, etc.). This process engineer allows for environmental shifting post process before measuring the final result.

The process engineer was having trouble with an ophthalmic AR coating shifting out of colour specifications after the coating was allowed to absorb atmosphere for 24 hours. The engineer designed the coating to shift into spec. An option we too often overlook.

Find the thread here on LinkedIn.

Tuesday, March 18, 2014

CHAMBER CHARATERIZATION

Characterizing your coating chambers is one of the most important things you can do in your lab. There's an old saying, "A good craftsman never blames his tools". The same goes for coating and your equipment. Know your tools and their capabilities and use them accordingly. Whether you're implementing a new design or process or just maintaining your equipment, knowing your coating chamber's characteristics is key to keeping your processes, new and old, within tolerance.

The most important thing is to know your material characteristics. Keep a database on each materials refractive index and physical properties for each coating chamber in your lab. Knowing the characteristics of your materials throughout the day and throughout the year will minimize coating runs that are out of spec and ease the implementation of new coating processes.

Characterize your coating chambers once every quarter. Add it to your preventative maintenance program. The optical performance of thin films will change season to season as the environment outside and in your lab change. It should only take a day or two to run all the materials used in a particular chamber and a confirmation coating for verification. It's well worth the time.

Characterization of a coating chamber requires more than just knowing the optical and physical properties of the thin films you deposit. You have to know the chamber too. Put your hands on it. Front and back. Top and bottom. Feel for temperature and vibration. Get to know when your equipment isn't running the way it's supposed to. A change in temperature by just a few degrees can change the outcome of your thin films.

For example, if you cool your chambers and associated equipment on city water rather than a constant temperature chiller, your processes may change from winter to summer as the water coming in will change by several degrees. Based on the temperature change of your cooling water your processes may need to be changed as the characteristics of the chamber change with temperature.

You're the craftsman and your coating chambers are your tools. Know them and their characteristics well so you can use them accordingly, effectively and efficiently.

Thursday, March 13, 2014

COATERS TECH APP FOR ANDROID

Coaters Tech has a simple app to display reflection and transmission based on substrate, medium and film refractive index data input. It's handy to have especially when you're characterizing your coating chamber.

Click to get it on Google Play, or search Google Play Apps for Coaters Tech.

To use the app just enter your values for refractive index. If a value is not entered the app defaults that field to a value of 1.

If you have any questions, comments or feedback please let me know. (My development devices are few so please let me know if you have trouble with the Coaters Tech app on yours and what device you are using)