Encapsulated silicone resin

The times at which microcapsules began to deposit on the electrode surface during the composite copper-plating are detailed in Table 9.3. The amount of deposited microcapsules was found to be directly related to and to the plating time. Microcapsules with a lube oil core were deposited later than the encapsulated silicone resin under the same D]. This showed that a higher and a longer time would be... 

Silicone resins find use as insulating varnishes, impregnating and encapsulating agents and in industrial paints. 

The protection of microelectronics from the effects of humidity and corrosive environments presents especially demanding requirements on protective coatings and encapsulants. Silicone polymers, epoxies, and imide resins are among the materials that have been used for the encapsulation of microelectronics. The physiological environment to which implanted medical electronic devices are exposed poses an especially challenging protection problem. In this volume, Troyk et al. outline the demands placed on such systems in medical applications, and discuss the properties of a variety of silicone-based encapsulants. 

After the sintering stage, electrodes are applied, usually either by electroless nickel plating or by painting or screening on specially adapted silver paint. Leads are then soldered to the electrodes when, for many applications, the device is complete in other cases it may be encapsulated in epoxy or silicone resins. Examples are illustrated in Fig. 4.15. 

The single largest use of silicone resins is as water repellents for stone and masomy. The resins also find important applications in paints and finishes, especially for high-temperature use, and increasingly as additives to conventional paints. Among the numerous speciality uses which have also been developed, siloxane resins are used to coat pharmaceutical pills and as encapsulants for electronic components. 

Fig. 6. Comparative SE images of an untreated Lower Triassic red sandstone and a red sandstone (both Wfistenzeller Buntsandstein) impregnated with a silicone microemulsion concentrate (SMK). a, b Untreated Mica layer surfaces (white arrows) and clay mineral fibers (illite, black arrow) without signs of polymeric encapsulation, c - f Impregnated with SMK d A detailed view fiom Fig. 6c clay mineral-mica intergrowlfas reveal structured silicone films on the prism plane of the cl mineral, e Clay mineral intergrowth with quartz, coated with a veil of silicone resin (white arrow) plan view of crystallogra]diic prism plane (110) or (010) (black arrow) plan view of sheet plane (001). f Detailed view from Fig. 6e day mineral perfectly encapsulated by structured silicone resin network.

Table 2 shows the physical properties of some potential encapsulants. Silicone gel has a high thermal expansion coefficient compared with that of other organic resins, but the generated thermal... 

Sylgard [Dow Corning]. TM for a series of silicone resin encapsulants used in electronic assemblies. 

Due to their small feature sizes, microelectronic circuits need protection from environmental hazards such as mechanical damage and adverse chemical influences from moisture and contaminants. Several approaches are currently in use, for example, hermetic encapsulation of the device in sealed metal or ceramic enclosures, application of soft silicone gels as a cover over integrated circuitry, and encapsulation by transfer molding, which is the topic of this report. Both silicone resins and epoxy resins are used for this purpose. As the quality and performance of the epoxy encapsulants improved, the need for the generally more expensive silicone resins diminished. The present work is exclusively devoted to epoxy transfer molding compounds. 

In this paper, the thermal stability of the silicone elastomers, base silicone resins, fillers, and their interactions with each other within the silicone matrix are described. Thermal decomposition volatiles, obtained indirectly through solvent extractables, reaction kinetics of the materials as integrated circuit (IC) devices encapsulants will be discussed. 

Silicones polymers which can take the form of fluids for lubrication, rubbers or plastics. Silicone resins are employed in electrical insulation applications, including component encapsulation. Silicone rubber is unique among synthetic elastomers being the only one with useful operating temperature, and resistant to weather, ozone, chemicals, with a non-stick surface. Silicones are used as release agents, because of incompatability with most materials, and as lubricants and additives. 

The basic chemical technology of silicones and silicone elastomers is covered in Chapter 18 so the discussion here is limited to silicone resins. These materials have many applications, including use in paints and varnishes, molding compounds, encapsulants, electrical insulation, pressure-sensitive adhesives, laminates, and release coatings. Their heat stability, water repellency, and resistance to solvents and weathering favor their use in these applications. 

Silicone resins are available in several forms. They are used as thermally stable electrical insulation resins, paint vehicles, molding compounds, laminates, impregnating varnishes, encapsulating materials, and as baked-on release agents. Recommended surface preparation is as follows ... 

Silicon—Ca.rbon Thermoset. The Sycar resins of Hercules are sihcon—carbon thermosets cured through the hydrosilation of sihcon hydride and sihcon vinyl groups with a trace amount of platinum catalyst. The material is a fast-cure system (<15 min at 180°C) and shows low moisture absorption that outperforms conventional thermosets such as polyimides and epoxies. Furthermore, the Sycar material provides excellent mechanical and physical properties used in printed wiring board (PWB) laminates and encapsulants such as flow coatable or glob-top coating of chip-on-board type apphcations. 

This paper reports the results of a molecular-level investigation of the effects of flame retardant additives on the thermal dedompositlon of thermoset molding compounds used for encapsulation of IC devices, and their implications to the reliability of devices in molded plastic packages. In particular, semiconductor grade novolac epoxy and silicone-epoxy based resins and an electrical grade novolac epoxy formulation are compared. This work is an extension of a previous study of an epoxy encapsulant to flame retarded and non-flame retarded sample pairs of novolac epoxy and silicone-epoxy compounds. The results of this work are correlated with separate studies on device aglng2>3, where appropriate. 

This structure has superior water-resistant properties in comparison to conventional polyols used for PU synthesis. Room temperature cures are easily obtained with typical urethane catalysts. Short chain diols, fillers and plasticizers may also be used in their formulations in order to vary physical properties. Formulations usually with NCO/OH ratio of 1.05 are used for this purpose. Such urethanes are reported to be flexible down to about -70 °C. HTPB is regarded as a work horse binder for composite propellants and PBXs. HTPB also successfully competes with widely used room temperature vulcanizing (RTV) silicones and special epoxy resins for the encapsulation of electronic components. HTPB-based PUs are superior in this respect as epoxy resins change their mechanical properties widely with temperature. 

---