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307 is a solvent-free, hot-curing adhesive film with high temperature and media resistance. At room temperature it is not tacky and can be easily cut to the shape of the bond area. Tackiness is developed at ca. 120°C, just before curing. This adhesive is used for bonding piezo ceramics in ultrasonic wave sensors onto metal surfaces where very low mechanical damping is required over a broad temperature range. It is also used for high temperature resistant structural bonding of PTFE layers onto aluminium with long-term temperature resistance up to 240°C.
Characteristics of Bismaleimide Adhesive Film
- Temperature resistant to 240°C
- Very high bond strength at high temperatures
- Very resistant to various chemicals
- Good bonds to aluminium, PTFE (Teflon®), and glass
- Improved easy and clean processing
Processing of the film
Surface pretreatment
307 should be prefereably used on carefully degreased and pretreated surfaces. Better joints are obtained on mechanically abraded and degreased surfaces, while chemical etching leads to best results. It is recommended to follow specific directions for surface pretreatments of various materials.
Application of Bismaleimide Film and Curing
The adhesive film can be cut to the shape of the bond area either manually or automatically. The transparent support film must be removed and the yellow adhesive film placed on one substrate. The second substrate should be placed on the adhesive film and fixed by mechanical clamps (or similar tools) for curing. Alternatively, the substrates can be heated to 120 °C. Upon contact with the hot surface, the adhesive film becomes tacky and sticks to the surface. The second hot substrate should then be placed on the adhesive and fixed for curing.
The adhesive film requires a minimum curing temperature of 150°C. Post curing at 200°C improves its properties significantly – especially its temperature and chemicals resistance. Only low fixing pressure is needed during the curing. The curing duration depends on how fast the adhesive can reach the needed temperature in the bond line. This is mostly governed by the thermal conductivity and the geometry of the substrates. As a guideline, curing should last for at least 30 min after reaching 150°C and 200°C, respectively. For first tests a curing schedule of 2h at 150°C + 2h at 200°C is recommended. Suitable tests under real-life conditions should be conducted by the user.
Chemical resistance
We tested the stability of adhesive joints in strong acids (sulphuric acid, phosphoric acid, at pH 1) and elevated temperatures up to 60 °C with good results. From experiments at customers we also know that solvent resistance is very high (acetone, methyl ethyl ketone, and N-methyl pyrrolidone were tested). We do not have much information about resistance in basic media (pH 10). Fuel resistance was tested in biodiesel and regular diesel with excellent results as well. However, it is important to note that the surface preparation of the bonded parts has a strong influence on the resistance of the overall adhesive joint. Water and other aqueous media are especially known to penetrate into the bondline and destroy the adhesion, even if the adhesive layer itself is still intact. Surface treatment with adhesion promoters (silanes) can often help in such cases.
Other informations about Bismaleimide Film
Storage and Disposal
307 may be stored in its original container between 4 and 35°C (do not freeze!). Avoid direct sunlight. Shelf life is 12 months. Expiry date is indicated on the label.
Spare amounts of the adhesive should be cured and then disposed of according to local regulations.
Handling precautions
When using the adhesive wear protective glasses and gloves. Refer to further instructions in the MSDS.
Final Advanced Materials provides also a full rang of epoxy adhesives.
Why is it important to prepare your surfaces before bonding?
The best way to ensure a long-lasting adhesive bond is to properly clean the parts before bonding them together. Our partner Bostik has developed a range of solutions under the Born2Bond™ brand specifically designed to cover all the different steps of the surface preparation process. These solutions are also recommended for adhesive bonding applications using Cotronics® products:
FAQs that can help you in this category
The choice depends mainly on the temperature and the mechanical stresses. Final Advanced Materials' high-temperature epoxy resins are generally limited to between 150 and 350°C, with satisfactory mechanical resistance (typical sheer-stress 10–30 MPa) and a degree of elasticity. However, the ceramic cements produced by Final Advanced Materials can be used up to 2,200°C, depending on the grade (alumina, zirconia, silicate, silica). They have excellent temperature resistance, but remain fragile (brittle behaviour, no elasticity). In the case of assemblies subject to differential expansion or vibration, epoxy is by far the preferred solution, if permitted by the maximum temperature of the application. However, in the case of extreme environments (kiln, vacuum, reducing atmosphere) which exceed 350°C, ceramic cement must be chosen.
The ceramic cements distributed by Final Advanced Materials have maximum working temperatures ranging between 650°C and 2,200°C. For example, alumina-based formulations often reach 1,650–1,760°C in an oxidising atmosphere. However, silicate systems are limited to around 1,000–1,200°C. The real maximum working temperature depends greatly on the environment (air, vacuum, inert gas), the time of exposure to this temperature and the thermal cycle (gradient, thermal shock). Specifically: the metal-loaded ceramic adhesives produced by Final Advanced Materials resist only up to the maximum temperature of the filler (650°C, for example, in the case of aluminium powder).
Ceramic/metal assemblies require often very different coefficients of thermal expansion (CTE) to be controlled. Final Advanced Materials recommends alumina-, silica- or zirconia-based ceramic cements for temperatures >350°C, which can bond to all types of ceramics and, generally, metals. For intermediate applications (≤350°C), an epoxy resin loaded with alumina powder enables thermal stresses to be absorbed and will be very compatible with different expansion coefficients. The thickness of the bond line must be between 100 and 300 µm to limit stress. Surface pre-treatment (sanding, degreasing, etc.) greatly improves adherence and is absolutely necessary if the CETs are very different.
The Cotronics adhesives distributed by Final Advanced Materials have variable cycles.
In the case of a cement, initial drying at ambient temperature takes between 2 to 24 h, depending on the viscosity and thickness. A thermal aftertreatment can be performed to allow them to attain their optimum properties after firing. Excessively rapid drying can lead to cracking or porosity in the cement.
Final Advanced Materials' epoxy adhesives which resist up to 260°C must be cured at ambient temperature. Epoxy adhesives which resist up to over 300°C require heat curing.