Aluminum encapsulants

For example, chloride and duoride ions, even in trace amounts (ppm), could cause the dissolution of aluminum metallization of complimentary metal oxide semiconductor (CMOS) devices. CMOS is likely to be the trend of VLSI technology and sodium chloride is a common contaminant. The protection of these devices from the effects of these mobile ions is an absolute requirement. The use of an ultrahigh purity encapsulant to encapsulate the passivated IC is the answer to some mobile ion contaminant problems. 

Scale prevention methods include operating at low conversion and chemical pretreatment. Acid injection to convert COs to CO2 is commonly used, but cellulosic membranes require operation at pH 4 to 7 to prevent hydrolysis. Sulfuric acid is commonly used at a dosing of 0.24 mg/L while hydrochloric acid is to be avoided to minimize corrosion. Acid addition will precipitate aluminum hydroxide. Water softening upstream of the RO By using lime and sodium zeolites will precipitate calcium and magnesium hydroxides and entrap some silica. Antisealant compounds such as sodium hexametaphosphate, EDTA, and polymers are also commonly added to encapsulate potential precipitants. Oxidant addition precipitates metal oxides for particle removal (converting soluble ferrous Fe ions to insoluble ferric Fe ions). 

Figure 116. Macro encapsulation in aluminum profiles with fins for improved heat transfer (Climator/Sweden)...

We use differential scanning calorimetry - which we invariably shorten to DSC - to analyze the thermal properties of polymer samples as a function of temperature. We encapsulate a small sample of polymer, typically weighing a few milligrams, in an aluminum pan that we place on top of a small heater within an insulated cell. We place an empty sample pan atop the heater of an identical reference cell. The temperature of the two cells is ramped at a precise rate and the difference in heat required to maintain the two cells at the same temperature is recorded. A computer provides the results as a thermogram, in which heat flow is plotted as a function of temperature, a schematic example of which is shown in Fig. 7.13. 

The change of capacitance in relation to the temperature is very small and a linear function of the substrate temperature. Unlike the change in metal film capacitors it is completely reversible. The maximum operating temperature of the capacitor chip (more than 200°) is determined by its aluminum gate. For encapsulated systems the bond contacts and the material of the package will determine the upper temperature limit. 

For reasons of corrosion in the vapor spaces and for ease of construction and cost, some floating cover designs have used nonferrous metals, primarily aluminum. Some designs have used encapsulated plastic flotation materials. These designs are generally considered more vulnerable to damage in a fire than those fabricated of metal components. API 650 and NFPA 30 classify these different designs as ... 

We now had acceptable rabbits for the short-term (polyethylene) and long-term (aluminum) irradiations. Since the internal volume of this rabbit design was cooled by primary cooling water flowing through the rabbit, samples were protected by encapsulation in polyethylene and quartz vials for the short- and long-term irradiations, respectively. 

The analysis scheme for the 10 evaluation samples used two aliquots ( 25 cm2 of filter paper/aliquot). One aliquot was encapsulated in polyethylene and irradiated in a polyethylene rabbit for 5 min in a thermal neutron flux of approximately 1014 n/cm2/sec. This sample was counted at decay times of 5 min, 30 min, and 24 hrs. The other aliquot was encapsulated in high purity synthetic quartz and irradiated in an aluminum rabbit 12-24 hrs. These samples were counted twice, after decay periods of 10 days and 3 wks. Sample counting equipment included one 4096-channel y-ray spectrometer and a Ge(Li) detector. 

The cobalt-60 source consists of 392 individually encapsulated rods (1). Each cobalt rod, which is 0.725 inch in diameter, is covered by a stainless steel jacket with welded end closures. This, in turn, is covered with an aluminum jacket (Figure 6). The doubly sealed slugs are 0.943 inch in diameter and approximately 10.7 inches long. The cobalt rods were encapsulated before activation in 1245 aluminum alloy to minimize activation... 

Three to 4 mg of extracted biopolymers was encapsulated in aluminum pans for the measurements. Each sample was first annealed at 200°C for 3 min. The melting point was determined using a Mettler DSC 30 Thermal Analysis System. Dry nitrogen was used as the flow gas with a flow rate of 30 mL/min, calibrated with indium and mercury. 

Particulate materials which have been studied in the encapsulation process include sodium chloride, sodium dichromate, lithium, sodium, lithium hydride, zinc, and lithium aluminum hydride. Typical experiments are described below. 

Example 1 Encapsulation of Lithium Aluminum Hydride with Poly(chloro-p-xylylene). In the distillation zone were placed 5.0 grams of dichloro-di-p-xylylene. In a 4-oz. polyethylene bottle were placed 10.0 grams (400 pellets) of lithium aluminum hydride (LAH). LAH was obtained from Metal Hydrides, Inc., as 1/8-inch diameter pellets. The bottle was positioned in the coating chamber, the system was... 

Attention was then turned to encapsulation of a more reactive species, lithium aluminum hydride (Example 1). Several batches were encapsulated readily with poly (chloro-p-xylylene) utilizing the standard tumbling process. Products with from 1-20 wt. % coating were prepared. 

---