Bismaleimides (BMI)

Bismaleimides - Imide extended Oligomers
Product	CAS	Description	Key attributes	Appearance	Viscosity	Applications
BMI-689	682800-79-9	A unique very low viscosity BMI resin	Toughener Hydrophobic High adhesion * Superior thermal stability	Yellow to Amber Liquid	1,500 ± 500 (25°C)	Base resin or additive in thermoset formulations designed for high temperature resistance
BMI-689M	1911605-95-2	A unique low viscosity liquid BMI resin	Low viscosity liquid BMI Hydrophobic Superior thermal stability	Dark Amber	5,000 ± 2000	use as an additive or base resin in adhesives that are designed for high temperature resistance
BMI-689C	-	A pre-catalyzed unique low viscosity liquid BMI resin	Pre-catalyzed Low viscosity liquid BMI Hydrophobic Superior thermal stability Solvent free	Yellow to brown Liquid	1,500 ± 500	use for thermal curing. A minimum of one hour at 150°C is a recommended starting point. Higher temperatures (up to 175 – 180°C) will result in significantly shorter cure time requirements.
BMI-1400	1224691-98-8	An amorphous, low molecular weight bismaleimide oligomer that exhibits good adhesion to a variety of substrates	Specialty formulated lower viscosity version of BMI-1700	Amber	6,500 ± 1,000 (60°C)	Film adhesives Pre-applied adhesives Adhesion to metal
BMI-1500	1290041-56-3	An amorphous, low molecular weight bismaleimide oligomer that exhibits good adhesion to a variety of substrates	Soluble in many reactive diluents Hydrophobic Superior thermal stability High adhesion to various substrates	Amber Viscous liquid	20,000 ± 10,000 (60°C)	Film adhesives Pre-applied adhesives Adhesion to metal
BMI-1700	1224691-98-8	An amorphous, low molecular weight bismaleimide oligomer that exhibits good adhesion to a variety of substrates	Soluble in many reactive diluents Hydrophobic Superior thermal stability High adhesion	Amber High Viscous Liquid	30,000 ± 10,000 (60°C)	Film adhesives Pre-applied adhesives Adhesion to metal
BMI-5000 Powder	921213-77-6	Imide-extended bismaleimide oligomer that exhibits excellent toughness in the cured state with intermediate cross-link density.	Low cross-link density Non-tacky Film-forming Maleimide functional oligomer Cures to a tough thermoset Additive to enhance toughness in thermoset compositions	Light Yellow Powder	N/A	Film adhesives Thermally resistant adhesives
BMI-6000	-	A curable, low DK and Df alternative to replace both the Kapton and adhesive layers in the manufacture of FCCL materials. It can be processed in a resin system as a solid or dissolved in a solvent.	Toughener Hydrophobic Super thermal stability Good dielectric properties Excellent workability High Tg Low CTE	Light Yellow Powder	N/A	Adhesive layer when laminating FCCL applications Adhesion promoter

Are there new products under development?

We are developing a couple of R&D resins with some unique properties:

FM46-100 is provided in a solvent solution (anisole) - after drying and "curing" it is a thermoplastic-appearing material with great elongation and the unique feature of returning to its original shape
The second (unclassified) material has the unique feature that after being formed into a film and deformed (folded, rolled up, etc.), it will hold that shape until warmed where it will then return to its original shape.

Can I use BMI with Acrylates?

Absolutely. Acrylates and methacrylates are regularly used in combination with Bismaleimides to modify die attach properties.

Acrylates are preferred because of their rapid curing, high Glass transition temperature, good adhesion,variable viscosities and variable functional group contents (1,2,3... acrylate groups per molecule). Of course nothing comes without drawbacks that can appear as potential brittleness and reduced moisture and temperature resistance.

What mix ratio do I use when mixing BMI with epoxy resin or acrylic?

The good news and the bad news is that there is no easy answer. In our experience we have encountered very few compatibility issues so virtually all BMI/acrylate or BMI/epoxy ratios are available to the formulators - it\'s just a matter of what they want for the final properties of the adhesive. Successful formulations have been created using 9:1 ratios of BMI as well as 1:6 ratios.

The BMI strong points (low modulus, good temperature resistance, hydrophobicity and good dielectric properties) lend themselves to the adhesive when blended with epoxies or acrylates since they share a cure chemistry. Therefore you can make adhesives with less stress, better moisture and temperature resistance but not totally lose the good aspects of an epoxy or acrylic chemistry.

How do I cure BMI systems?

BMI resins cure free radically - whether thermally by the use of an organic peroxide catalyst or even by UV if using a free radical generating photoinitiator. DMI's preferred thermal catalyst is dicumyl peroxide (CAS # 80-43-3). We recommend using ~2% by weight of the resin content of the formulation and then curing at ~175ºC for an hour.

Of course, these values are just starting recommendations and your application and formulation may require other settings. There are a number organic peroxides that work well to thermally cure the BMI and BMI/acrylate resins.

Comparison between BMI based die attach and Epoxy based die attach

	BMI	Epoxy	BMI/Epoxy
Modulus	●○○○○	●●●○○	●●○○○
Moisture absorption	●○○○○	●●●○○	●●○○○
Thermal stability	●●●●○	●●○○○	●●●○○
JEDEC level 1 / 260 °C	Yes	No	Yes
Adhesion to substrate	●●●○○	●●●●●	●●●●○
100% solids	Yes	No	Yes
Snapcure option	Yes	No	No
Material cost	●●●○○	●○○○○	●●○○○

Amorphous and liquid imide extended oligomers

BMI Curing Methods

DMI aliphatic BMI resins (689, 3000, 1500, 1400, 1700, 2500) can be cured in a number of ways:

1. Thermal Cure. The most preferred method that gives the most complete cure uses thermal free radical generating catalysts. These catalysts are mainly peroxides that decompose at given temperatures to initiate the polymerization. There are a number of available catalysts but our all-time favorite is Dicumyl Peroxide (DCP). When using about 2 wt% of the resin this material will cause the BMIs to start curing at about 140ºC, peak at about 155ºC. We suggest curing at 175ºC for an hour to insure a thorough cure. You can cure hotter/faster or slower/longer - it is important to experiment to determine the best setting for their application. Another favorite peroxide catalyst is Perkadox 16. This is a low temperature catalyst that starts to cure the resin below 100ºC. This is good for rapid curing adhesives (like die attach paste). The down side is the catalyzed material must be frozen, shipped in dry ice and the pot life will be much shorter than that of a DCP catalyzed system.

2. UV Cure. The BMI products cure via free radical initiated polymerization. One may use a photoinititator (UV catalyst) to prompt curing of these materials. Our favorite is Irgacure IR 819. This catalyst provides the free radical groups necessary to polymerize the resins upon exposure to 500 - 1,000 mJ/cm2 i-line (365 nm) UV radiation. This is beneficial as it occurs at room temperature and keeps the stress levels low. (Many) Other UV catalysts can also be used.

3. Homocure. You can cure the BMI-689 and BMI-1400 simply by heating them above 220ºC for an hour or two and they will self cure (homocure). This is the least preferred method of curing because 1) it\'s really, really hot and few applications can tolerate the heat and 2) it provides a less thorough cure than other methods.

BMI recommended storage conditions and shelf life

We recommend storage of our liquid BMI resins at 5ºC or colder and away from sunlight (UV sources). For the solid resins we suggest room temperature storage and away from light. DMI warrants the performance of the materials (shelf life) for 1 year from the date of shipment of the products (not the date of manufacture) if stored per recommendations. This insures a guaranteed full year of use of the materials after receipt.