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|Photopatternable Laminate Dielectric|
|Keywords: Dielectric, Laminate, Photopatternable|
|Divinyl Siloxane Benzocyclobutene (DVS-BCB) has been recognized as an outstanding dielectric material for many years. Recently the concept of creating a laminate film utilizing DVS-BCB as a primary component has been introduced. The exceptional mechanical and electrical properties of DVS-BCB including high thermal stability, low moisture uptake, low dielectric constant, and low dissipation factor must be maintained. However, difficulty exists in that DVS-BCB alone is too rigid to produce a high quality laminate film. As the flexibility is improved to produce a film, better fracture toughness (K1C) and higher elongation should result. Novel formulation adjustments to the base DVS-BCB polymer system have resulted in an experimental laminate dielectric product that will be the focus of this discussion. Depending on the application, laminate films can vary in thickness from 2µm to 50µm or thicker. The typical film base sheet is optically clear polyester (PET) with a polyethylene (PE) cover sheet. The DVS-BCB based laminate can be tuned with appropriate additives to either pattern with UV exposure from a tool such as a Suss Mask Aligner (50mJ/cm2 - 100 mJ/cm2 exposure energy), or laser pattern with a tool such as a 248nm Suss Excimer Laser Stepper. Aspect ratios of 1:1.5 have been achieved with a photopatternable DVS-BCB film and aspect ratios of > 1:1 are possible with a laser patterned film. Besides photopackages added to the film to enable UV curing and patterning, toughening additives have also been incorporated to enhance the K1C and elongation properties. K1C for the laminate has been improved to 0.55Mpa•m1/2 vs. 0.35Mpa•m1/2 for DVS-BCB. Elongation has been improved to > 20% for the laminate vs. 8% for DVS-BCB. Electrical properties are in need of confirmation although it is expected that the laminate will maintain similar values to DVS-BCB. An additional strength of the laminate dielectric is the ability to tent over and protect vias. Vias > 300µm diameter have successfully been tented with a 10µm thick film. A DVS-BCB based laminate has been demonstrated with continued optimization and evaluation to follow.|
|Corey O'Connor, Scientist
Dow Electronic Materials