Evaporation boats are used in vacuum metallization processes to heat metallic materials to high temperatures. There are two main types of boats - two-component boats made from titanium diboride and boron nitride, and three-component boats which also include aluminum nitride. Two-component boats are preferred as they are more durable and higher quality. The production of evaporation boats is an expensive process requiring specialized equipment and materials. During metallization, the boat is heated to 1500°C to evaporate a metal which is then deposited as a uniform coating on a substrate. Important properties of boats include wettability, corrosion resistance, electrical resistivity, and toughness, which determine the boat's performance and lifespan

1. Evaporation Boat for
Vacuum Metallizing : An
Overview
Anshuman Punj

2. Vacuum metallization processes usually employ evaporation boats made ofinter-
metalliccompositeor IMCmaterials. Theseboats areoftwo types –
A) – 2 Component Boat – This type of boat is made with Titanium Diboride
(Conductor) andBoron Nitride(Insulator).
B) –3ComponentBoat–This is madewith TitaniumDiboride(Conductor), Boron
Nitride(Insulator) andAluminumNitride(Insulator).
Compared to three component boat, two component boat is longer lasting and of
better quality. In three component boat, Aluminum Nitride is added to bring
down the cost. But consequently, it is lower in life and quality as well. Hence,
users prefer 2 componentboats to 3componentones.
Production of Evaporation Boats is very expensive, involving heavy, costly
machinery (hot press), raw materials and running energy costs. Also it is
protected by patent laws. Therefore, very few companies in the world are
producing it.
In the metallization process, the evaporation boat is heated to temperatures
around1500 °Cby applying an electriccurrent. Metallicwire(usually high-purity
aluminum wire) is continuously fed to the top surface of the evaporation boat.
Thesurfacearea andthestability ofthemetallicpuddleon theboatlargely decide
therateofevaporation as well as how uniformly thefilmforms on thesubstrate.
Meanwhile, the metal melt seeps inside the boat and acts like a corrosive acid, causing
cracks, fissures and deteriorating the boat over time.
Important properties of Evaporation Boat-
Introduction
Evaporation Boat for Vacuum Metallizing : An Overview

3. 1. Wettability – Ceramic boats typically undergo a transition from non-wettable
to wettable at temperatures between 1250 –1400 °C. The more wettable a boat
is, themoreuniformcoating will itdeliver.
2. Corrosion resistanceto molten metal –Thereis a strangeparadoxbetween the
properties of wettability and corrosion resistance. On one hand it is highly
desirable for the boat to be wettable and on the other hand, it is this very quality
that corrodes the boat. Molten metal on the boat causes a corrosive reaction,
forming deep grooves on the boat. These grooves continue to deepen and crack
theboat, causing prematurefailure.
3. Electrical resistivity – A boat with low electrical resistivity will readily allow
electrical current to ow through it, thereby failing to heat up. On theother hand,
highest electrical resistivity is limited by metallizer's power supply. Therefore, it
is desirable that the boat be of optimum electrical resistivity so that it heats up
slowly, allowing aluminumto melton itandcauseuniformcoating.
4. Toughness, and crack resistance - A delicate balance needs to be struck
between the properties of wettability and corrosion resistance. Increased boat
lifedecreases machinedown timeandtheoverall boatcosts.
Some other things to keep in mind for over-all boat performance-
1. Theceramicboatshouldnotbeexposedto humidity beforeuse.
2. It should not interfere with the vacuum process by emitting non-desirable
gases.
3. Atthetimeofassembly, theboats shouldbeproperly clamped.
Evaporation Boat for VacuumMetallizing : An Overview
Evaporation Boat for Vacuum Metallizing : An Overview

4. 4. Consistentanduniformpower supply to theboatshouldbemaintained.
THE PROCESS OF BOAT MANUFACTURING
Although various companies manufacture evaporation boats in varied shapes,
the most common shape is rectangular. Tests have proven this shape to be the
best for industrial scale vacuum coating. Also, this shape is very easy to handle,
making itoperator friendly.
Thereare5 basicsteps in theproduction ofEvaporation Boats:
Preparing thepowders
– First of all, the powder particles are brought down to the desired size through
milling.
Blending oftheraw materials
– The powders are mixed together in the desired ratio and blended thoroughly
for thesakeofuniformity in theraw material.
Hot-pressing
–Theblended raw material is then hot-pressed ata very high temperature(More
than 1500 C) with a pressure of more than 150 tons. This delivers a big block of
ceramic.
EvaporationBoat for VacuumMetallizing : An Overview
EvaporationBoat for Vacuum Metallizing : An Overview

5. Machining
– The hot-pressed ceramic block is then cut into boats with a diamond cutter.
Each boat is ground for a smooth nish and dimensional accuracy. A cavity is
groundinto each boat.
Quality control
–Each and every boat is measured for resistivity. After nal inspection, boats are
packedfor shipping.
Evaporation Boat for Vacuum Metallizing : An Overview

6. Supervac Industries makeEvaporation Boats known with the brand name – ALFA ONE
– These are made in various sizes and resistivity as per the customer’s requirement.
ALFA ONE boats come with Supervac Industries’ stamp of world- class quality and
reliability.
For further enquiries -
Address: B-21, Flatted Factory Complex, Jhandewalan, New Delhi-110055 (India)
Phone number (landline): +91-11-2353 7331, +91-11-4355 4966, +91-11-4356 4967
Email: info@supervacoils.com, sales@supervacoils.com
Contact Persons: Anshuman Punj Contact Number: +91-9810144936
Archishman Punj Contact Number :+91 -8860868196
Thankyoufortaking thetimeouttoreadthiswhitepaper. HappyMetallizing.