Kurt R. Grebe

Effects of parylene coating on the thermal fatigue life of solder joints in ceramic packages

A study was undertaken to determine the effectiveness of a thin layer (9.4 mu m in thickness) of a chemical vapor deposited polymer, parylene, in enhancing the solder lifetime of a ceramic package containing large-DNP (distance to neutral point) test chips. Both coated and uncoated (control) packages with chips joined via C4 Pb/Sn solder technology were thermally cycled near room temperature and liquid nitrogen temperature (-196 degrees C) until solder failure was first noticed in coated packages. The number of cycles to first failure for coated packages was found to be twice the corresponding number for uncoated packages. To interpret this twofold solder life enhancement, an elasto-plastic finite-element model was developed. Based on the results provided by this model and a low-temperature solder lifetime model, it was possible to attribute the extended solder life to the modification of the strain and stress fields in the solder joints by the parylene coating. The model also suggests that the solder life can be prolonged significantly with a parylene coating as thin as 3 mu m. >

An approach towards batch fabricated ferrite memory planes

This paper describes a technique for the batch fabrication of ferrite memory arrays in which wire, previously coated with a thermoplastic, is formed into two orthogonally disposed sets of parallel wires. These grids are oriented between opposingm olds having matched grooves filled with a fluid mixture of ferrite powder and thermosetting resin, in such a manner that one set of parallel wires coincides with the groove axes. After suitable curing this structure is released and heat treated to pyrolyze the organic materials and sinter the ferrite. A yield study on 108 memory arrays produced in this manner resulted in a yield of 72.2% on pulse testing under simulated operating conditions and an over-all process yield of 36.1%. The paper concludes with a tabulation of electrical characteristics of the arrays and a brief discussion of the applicability of the technology to various modes of operation and its potential for high-speed (250 nsec magnetic cycle time) operation.

Filters for soft x-ray solar telescopes

Soft x-ray telescopes require filters that block visible and infrared light and have good soft x-ray transmission. The optical properties of possible materials are discussed, and the fabrication and testing methods for the filters used in a 10-inch normal incidence telescope for X = 63 A are described. The best performances in the is. 44-1 14 A wavelength range are obtained with foils of carbon and rhodium.

Filters For Soft X-Ray Solar Telescopes

Soft x-ray telescopes require filters that block visible and infrared light and have good soft x-ray transmission. The optical properties of possible materials are discussed and the fabrication and testing methods for the filters used in a 10 inch normal incidence telescope for λ = 63Å are described. The best performances in the λ = 44 114Å wavelengths range is obtained with foils of carbon and rhodium.