Conveyor furnace, furnaces for the electronic industry
Koyo Thermo Systems is represented in Europe by
Crystec Technology Trading GmbH
Conveyor Furnace, Furnaces
There is a wide range
of conveyor furnaces for many applications like firing of thick films, firing of condenser
electrodes, firing of thermal heads, all types of sealing and annealing and drying,
soldering, brazing, re-flow, and resin curing. Special clean conveyor
furnaces are used in FPD production. On this page we give
you an overview over the equipment available for these applications. These can be operated under air or protective gas or inert gas such as nitrogen (N2) and argon (Ar). However
this is not a complete list. Please contact us
if you need further information.
|Conveyor furnaces for thick film firing
Thick film technology is used to manufacture single
electronic parts like resistors and capacitors, hybrid circuits,
heating elements, sensors and display systems. The substrate materials
are ceramics (Al2O3, AlN, BeO2, ZrO2),
glass, PCB's, metals covered by an insulation layer (Porcelain Enameled
Steel) and thermal print heads. Thick film material can be based on low
melting glass, CERMET, polymers or organometallics.
Thick film paste contains binders and solvents. The first step is
a pre-drying to remove solvents. After that, a special firing procedure
is to be carried out in order to remove binders and to get the desired
parameters. There are two important things: temperature profile and gas
flow. The temperature-versus-time profile is given by the thick film
The thick film layers are mostly deposited by screen printing. In special cases they are
structured by photolithography too.
There are standard profiles for CERMET pastes among the many
special processes, different by a total heat treatment time from 30 to
60 minutes. These profiles have a plateau at 850°C for 10 minutes.
During heating up to 600°C the binder burns out. The zone in the
furnace where this occurs is called the burnout zone.
After burning out, the film is fired up to
850°C in order to get the right electrical and mechanical data.
Last, the treated films must cool down. A thick film firing furnace is
equipped with a special air flow system. The evaporated binder has to
be sucked away, keeping the firing area free from contamination. All
feeding air has to be very clean, particularly free of oil and water
(dew point less than -50°C).
|suitable for the following temperatures |
This MT type furnace is equipped with a
high-precision temperature controller and a muffle which contribute to
higher attainment of atmosphere stability and repeatability in the
Atmosphere stability is assured by purge chambers at the inlet and
at the outlet. A forced exhaust system is installed with
an ejector that is located at the best burnout position.
For both side firing of samples special holders can be installed
on the metallic chain.
Temperatures up to 1400°C are possible.
Here are some applications for firing of
special thick film pastes:
Metallisation pastes are fired between 500 and
950°C depending on the system used. Brazing paste of Cu/Ag eutectic type is brazed in
wet H2 or cracked ammonia (forming
gas) at 800 - 840°C.
Special firing of base-metal pastes (Cu paste)
The firing of copper paste requires special gas control because of the
susceptibility to the influence of air. Therefore, a nitrogen atmosphere
furnace is needed to keep the inside oxygen concentration less than 5 ppm.
Special firing of overglazes and underglazes
Resistor overglazes are usually fired between 500 and 600°C (typically
at 525°C). Thermal print head underglaze is fired in the range of 850
to 930°C and thermal print head overglaze is treated at 850°C.
Other special overglaze have to be fired in the same range between 500 and 930°C.
Sealing temperature depends on seal thickness, sealing time, application.
The temperature range for firing of sealing glass is between 400 and 675°C.
Polymer conductors, dielectrics and protective coatings.
Polymer conductors are based on silver filled phenolic (cure temperature
at 150 - 220°C) or acrylic for lower cure temperatures (at 80 - 120°C). Dielectric and
protective coatings are based on silicone or epoxy with a cure range of 125 - 200°C.
|Clean and high temperature applications
A speciality of Koyo Thermo Systems are
special versions of conveyor furnaces for clean and/or high temperature
applications. conveyor furnaces can be equipped with quartz glass
muffles and with ceramic chains. Ceramic chains are available in
different sizes and materials.
|suitable for the following temperatures |
|Brazing and soldering furnace
Meshbelt transport is used in this
soldering furnace. Temperature is 260°C. The furnace has
a downstream gas flow and can be run under nitrogen atmosphere or
using a reducing atmosphere (forming gas). Full consideration has been
taken on safety mechanisms and for easy handling of the equipment.
For lead free soldering, Koyo developed recently a
conveyor furnace with a walking beam transport system which causes very
few vibrations. Details are available on request.
|High precision small conveyor furnace type 810
This is a small conveyor furnace of
high performance in heating and cooling at low costs. LGO heater is
equipped for simplifying the design and to reduce the weight.The touch
panel provides an excellent maneuverability. It can be used in a wide
range of applications for not only laboratory and development but also
small lot production, high precision treatment and so forth. It can be
operated from 350°C - 1000°C. Dimension is 530 x 1355 x 3000 mm3
(W x H x L). Belt width is 100 - 200mm.
|IR conveyor Furnaces for Drying Thick Film Pastes.
Mainly for drying of thick film pastes,
Koyo Thermo Systems developed a conveyor furnace that uses infrared
lamp heating. The temperature uniformity at 130°C is
|Hot plate heating equipment
Two different types of hot plate
heating equipment is also available from Koyo Thermo Systems. First
version transports the wafer by a teflon belt, second version uses a
shuttle transport system. In both cases wafers are processes one by
one. Max. temperature is 150°C / 200°C.
|Roller hearth continuous furnaces
Roller hearth furnaces have been
designed to anneal large and heavy samples. The transport inside this
clean, horizontal, continuous furnace is done by stainless steel rods.
In order to avoid metallic contamination, ceramic tubes, made of
pure alumina can be installed over these steel rods. All roller hearths
are driven by a special chain transmission system that avoids slip
during the transport of the samples. The furnace itself consists of a
special glass muffle and far IR Moldatherm® heaters. An
advanced temperature control system ensures a temperature uniformity of
less than 1°C. This furnace can be used for annealing of glass plates in plasma display panel production.
Conveyor furnaces consists of different types of muffles and in most
cases Moldatherm® heating elements. In some cases SiC-heaters,
IR lamp heating, convectional heating or hot plate heating is used.
|Moldatherm® Heating Elements
elements consist of special heating wire that is vacuum molded into a
ceramic fiber isolation material. Moldatherm® heating
elements have a low heat capacity. They have very similar properties
compared to the LGO heating elements, used
in semiconductor furnaces.
Moldatherm® heating elements assure an easy
maintenance of the conveyor furnace. Moldatherm® heaters
are compact and light. The furnace is built by blocks of Moldatherm®
heaters. The installation can be done easily and quickly. No
special tools are required for this work.
Many different transport systems are used in Koyo Thermo Systems
conveyor furnaces, e.g.:
- Mesh belt transport (MB-type)
- Metallic chain transport (MC type)
- Ceramic chain transport (CC type)
- Walking beam transport (WB type)
- Teflon belt transport (TB type)
- Roller hearth transport(see PDP processing equipment).
Loading can be done manually or automatic. Koyo Thermo Systems can
provide different loading and unloading systems. Different process
gases can be used in Koyo Thermo Systems furnaces, like inert gases, forming gas
or hydrogen. The oxygen content can be measured,
using an oxygen analyzer. As an option
in many cases a Stange controller can be
used. That way it is possible to connect the furnace controller to a
Please also visit our special page for conveyor furnaces and
ovens for flat panel production (FPD).
Koyo Thermo Systems and Crystec will be pleased to engineer a cost effective system to satisfy
your most demanding and exacting requirements.