Operation and installation of evaporation boat
Operation of the evaporation boat
1. When using a new evaporation boat, control the accurate time through screen
operation, gradually increase the voltage for 5 minutes each time, and then increase
it again (such as 7v-8v-9v). Or start according to the program set by the aluminum
plating machine. Gradually increase the pressure to heat the evaporation boat for
annealing, in order to release internal stress, and at the same time, the gas absorbed
inside the boat material is also released. The aluminum wire melts with the evaporation
boat and takes about 20 minutes to wet. Wetting too quickly will reduce the stability
of the evaporation gas and greatly shorten the service life of the evaporation boat.
2. The longer the operation time, the hotter the evaporation boat. It is necessary to
maintain a continuous decrease in voltage (depending on the splashing phenomenon).
When the voltage drops, pay attention to reducing the feed rate of the aluminum wire.
During continuous production, the voltage of the evaporation boat at the end of the
first roll of film evaporation is lower than the voltage at the start of the evaporation
boat. The time required to lower the voltage of a high resistance evaporation boat
(650MOC) is longer than that of a low resistance evaporation boat. The resistance of
almost all substances changes with temperature, and usually, as the temperature
increases, the resistance also increases. The high-temperature resistivity at 15000C is
the resistivity used and finalized in the design of the evaporation boat, which is
matched with the evaporation power supply. (High temperature resistivity is several
times that of room temperature resistivity)
3. After the first use of the evaporation boat, gently clean the aluminum slag on the
surface of the boat groove with a brush, and use a steel wire brush to clean it every
time it is used in the future. After each cleaning operation, check the evaporation
boat to ensure it is clamped. Otherwise, it will jump during startup.
4. When starting the evaporation boat, but one of them is not lit, do not continue to
send aluminum wire to generate arc light until it ignites. You should first adjust the
aluminum wire to approach the evaporation boat forward, and then start the evaporation
boat to ignite it. Otherwise, not only will it damage the fixture, but it will also damage
the evaporation boat and shorten its lifespan.
5. The evaporation boat with the largest aluminum adhesion surface has a wider
evaporation range, easy control of the evaporation coating, and the longest continuous
evaporation time.
If the evaporation temperature is too high, the evaporation rate will increase, but the
evaporation mode is more perpendicular to the direction of the thin film evaporation.
(The evaporation rate of aluminum will increase by about twice for every 750C increase
in evaporation temperature)
When the working temperature of the evaporation boat increases, the area of the boat
groove used will decrease, and as the temperature increases, the corrosion rate of ceramic
materials will also increase exponentially. The decrease in evaporation angle will also lead
to a decrease in the lateral uniformity of the coating. (Causing black streaks during evaporation)
The quality of evaporation and the lifespan of the evaporation boat directly reflect the
operator's ability to control the temperature of the evaporation boat and the adhesion area
of the aluminum surface. The treatment of the contact surface formed by aluminum on the
evaporation boat during its first wetting is crucial. The lifespan that an evaporation boat can
achieve depends on the size of the surface area formed by the molten layer of aluminum on
the boat during the first operation. When the coverage area of liquid aluminum decreases,
the reduced liquid aluminum area will be covered with a layer of aluminum slag. Once this
aluminum slag is generated, a higher boat temperature is required to maintain the original
evaporation wire feeding rate, thereby shortening the life of the evaporation boat
The operator strives to minimize the temperature of the evaporation boat as much as possible
(the color of the evaporation boat should be bright orange, white indicating too high
temperature, and red indicating too low temperature), as well as the cleaning steps after each
roll of evaporation plating, and carefully increases the coverage of liquid aluminum on the
contact surface as much as possible.
6. When coating packaging film, the general evaporation rate of aluminum wire is 0.3 gms/cm2/min,
which can achieve a good balance between the coating speed, the lifespan of the evaporation boat,
and lateral uniformity. At this rate, the area of the boat trough is 25-30 cm2 (with an evaporation
boat heating power of 85%), reaching an evaporation capacity of 6.6 gms/min. The operating
temperature of the evaporation boat is about 15350C, and its lifespan is 15-20 hours.
The lifespan of the evaporation boat is directly affected by the temperature of the working environment.
The evaporation boat is made by pressing 2 to 3 types of ceramic powder, which is a mixture of
titanium borate (TiB2) conductive powder and insulating boron nitride (BN) powder. Aluminum
nitride (ALN) is sometimes used as a component to increase the bending strength of the ceramic
and its wettability to aluminum. When using the evaporation boat, aluminum will penetrate the
surface of the boat between titanium borate (TiB2) molecules and react with boron nitride (BN)
to generate ALN and B. B continues to react with AL to generate ALB12. Similarly, aluminum
oxide (AL2O3) enters the surface of the boat trough from the surface of the aluminum wire and
reacts with BN and B to generate B2O3 and ALN. Titanium borate (TiB2) and aluminum nitride
(ALN) both generate gaseous compounds and escape at standard vaporization temperatures,
while boron nitride (BN) decreases, which determines the lifespan of the evaporation boat. The
higher the temperature, the faster the reduction of boron nitride (BN) and the shorter the
lifespan of the evaporation boat.
Installation of evaporation boat
The length of the clamping parts of the boat clamps at both ends of the evaporation boat
should be consistent and ensure good electrical and mechanical contact to avoid generating
additional heat on the boat clamps. Ensure consistent temperature on both sides of the boat
to prevent it from bending. Insert the evaporation boat into the graphite sheet and boat clamp,
as excessive pressure can cause the boat to crack. If the installation of the new boat is too loose
or too tight for the first time, you should refer to the manual of the boat clamp. Operators should
pay great attention to the machining tolerance of the evaporation boat (the length, width, and
parallelism of the boat are all very important.) Use graphite sheets to eliminate the gap between
the boat and the boat clamp and improve their contact. There should be sufficient pressure
between the two ends of the boat and the boat clamp, while also ensuring that the boat can
expand and expand during heating. The aluminum oxide should be removed from the active side
of the fixture.
2. When loading the boat, a certain inclination can be maintained (with the aluminum wire end
slightly higher), which is conducive to the flow of liquid aluminum to the end of the boat. This is
important for increasing the spreading area of liquid aluminum, improving the lifespan of the
evaporation boat, and improving the uniformity of the coating. The evaporation boat should be
kept horizontally.
3. During actual coating, the aluminum wire should be sent to the 1/3-1/2 position of the boat,
and the operator should consider the factor that the aluminum wire will sag when the boat
temperature is high. At the same time, the aluminum wire should also be sent to the centerline
position of the boat slot.
4. Avoid contact with the surface of the boat groove to avoid contamination, which will reduce
the wettability of the boat groove surface to liquid aluminum.
5. After opening the packaging, avoid getting water on the surface of the boat. The boron nitride
components in the boat are easy to absorb water, which can vaporize and expand during heating,
leading to boat explosion.