Conveyor furnace, furnaces for the electronic industry.
	Koyo Thermo Systems Co., Ltd. is represented in Europe by Crystec Technology Trading GmbH
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Conveyor Furnace, Furnaces

Koyo Thermo Systems is producing 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. However this is not a complete list. Please contact us if you need further information.

Conveyor furnaces consists of different types of muffles and in most cases Moldatherm^TM heating elements. In some cases SiC-heaters, IR lamp heating, convectional heating or hot plate heating is used.

Moldatherm^TM Heating Elements

MoldathermTM heating elements consist of special heating wire that is vacuum molded into a ceramic fiber isolation material. MoldathermTM heating elements have a low heat capacity. They have very similar properties compared to the LGO heating elements, used in semiconductor furnaces. MoldathermTM heating elements assure an easy maintenance of the conveyor furnace. MoldathermTM heaters are compact and light. The furnace is built by blocks of MoldathermTM 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.:

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 PC-network. In the following section we show you some examples of Koyo Thermo Systems conveyor furnaces:

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.
The thick film layers are mostly deposited by screen printing. In special cases they are structured by photolithography too.
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 paste suppliers.
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).

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 furnace.
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

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 glasses

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

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 ±5°C.

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 MoldathermTM 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.

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.

Crystec Technology Trading GmbH will be pleased to further discuss details with you.
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