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LOCTITE ABLESTIK QMI536NB is a low-bleed, non- conductive, PTFE-filled paste designed for stacked die applications which require very low stress and robust mechanical properties. The material has the same processing and properties of QMI536 but resin bleed is essentially eliminated. These features produce fast cure capability and enhanced reliability performance to a wide variety of surfaces, including solder resist, flexible tape, bare silicon and various die passivations.
LOCTITE ABLESTIK QMI536NB creates packages and devices that have high resistance to delamination and popcorning after multiple exposures to lead-free solder reflow temperatures. It has good optical performance with high transmittance, Optical Density and HRI and is a great solution for ASIC attach and LED attach.
LOCTITE ABLESTIK QMI536NB is a Bismaleimide (BMI) based product. QMI products are typically lower modulus at 25C vs epoxies and therefore lower in strength. They make up for it at higher temps where they are typically higher in strength than epoxies, something very beneficial during reliability testing. At the same time their lower modulus (“flexibility”) is also leading to less stress during temp cycling, temp shock and vibration testing. Because of their high temperature stable and hydrophobic properties, such BMI materials have replaced many epoxy die attach materials when Pb free 260 reflow had to be survived.
The DMA Modulus curve shows the modulus of the QMI536NB over the temperature range from -100°C up to 300°C
Pull strength of Bismaleimide based resins in different tempsIt has been observed that BMI based hybrids do not perform well on pull tests. BMI resin based QMI products are typically lower modulus at 25°C vs epoxies and therefore lower in strength. But, and that's the most important point, at higher temps they are typically higher in strength than epoxies, something that benefits high temp operation applications up to 200°C !
This lower modulus (“flexibility”) is also leading to less stress during temp cycling, temp shock and vibration testing.
Since it contains silanes, is this a silicone or an epoxy based resin?
BMI resin based adhesives are Silicone free! Silanes are added in small quantities as adhesion promoter. And to add to that since you're wondering how to classify it, we’re not aware of any BMI/epoxy cross contamination.
What is Optical Density?
Optical density is a logarithmic intensity ratio of the light falling upon the material, to the light transmitted through the material:
Though optical density and absorbance both measure the absorption of light when that light passes through an optical component, these two terms are not the same. Optical density measures the amount of attenuation, or intensity lost, when light passes through an optical component. It also tracks attenuation based on the scattering of light, whereas absorbance considers only the absorption of light within the optical component. Src
It is usual a point of confusion since people sometimes say it is the same as absorbance or define it as absorbance over the length.