The results obtained from Moisture-Temperature-Bias testing of Power- MOSFET at 130°C and 85%RH are examined. A variety of packaging techniques were tested varying from plastic encapsulation materials/methods to fully hermetic. Unprotected devices were tested as controls. The predominant failure mechanism observed was aluminum corrosion, which was manifested initially as a leakage current increase and eventually as visually observable dissolution of aluminum and eventual open circuits.

This paper examines the critical part that surface contamination plays in the corrosion process, particularly where condensed water films can form at the metal surface. The effectiveness of various plastic coating methods are viewed in the light of this concept. Aluminum lead bonds were more susceptable to corrosion than expected. A number of materials were identified that showed resistance to pressure cooker conditions.

The interdiffusion in thin films of polyimide has been investigated using the forward recoil spectrometry (FRES) technique. Films 5–10 μm in thickness of polyamic acid spin coated onto a silicon substrate were imidized at a temperature TI. A second film, ∼300Å in thickness of perdeuterated polyamic acid was spin-coated onto the first layer and heated to a temperature TD to allow interdiffusion of the two films and imidization of the second coating. Depth profiling of the deuterated polymer by FRES showed that no interdiffusion occurred if TI>TD and TI>200°C. Substantial interdiffusion occurred if TD>TI and TI<400° C. Time averaged tracer diffusion coefficients were found to vary with the TD and TI, as well as the length of time allowed for interdiffusion. Since conversion of the deuterated polyamic acid to polyimide occurs at the diffusion temperature, the results are consistent with a relatively large diffusion coefficient for the polyamic acid (D>2.5× 10−14 cm2/sec) which decreases to a negligible value as the molecule is fully converted to the corresponding polyimide.

Impurities, especially chemically bonded impurities, of o-cresol novolac epoxy resins and their influence on the moisture resistance and other properties of the epoxy molding compounds have been investigated to clarify the influence of impurities of epoxy resins on the reliability of encapsulated semiconductor. As a result, the existence of hydrolyzable chlorine and hydroxyl group-containing impurities has been confirmed, and it was found that the impurity such as a hydrolyzable chlorine causes undesirable influence on both the moisture resistance and electrical properties at high temperatures. It was also found that the impurity such as a hydroxyl group causes undesirable influence on the moisture resistance, and that the lower hydroxyl content gives the higher heat resistance as a result of an increase in the epoxy content.

When thin adhered films of a polyimide (Ciba-Geigy XU-293) on rigid substrates are immersed in xylene, defects, that look like cracks to the naked eye, are formed. These defects are caused by the presence of the combination of the equibiaxial tension in the film and the xylene. The stress comes from the solvent loss and the thermal expansion mismatch between the substrate and the film. The defects are found to be local deformation zones, showing considerable optical anisotropy and a microstructure strongly influenced by the adhesion condition to the substrate. Although they retain a smooth surface on the face in contact with the substrate in the bonded regions, the deformation zones release a significant amount of stress. The stress released is measured by a photoelastic technique and is found to be in excellent agreement with that calculated from the local thickness change assuming simple elasticity. These deformation zones grow at a speed that is independent of their length and initiation time but increase rapidly with film thickness from a threshold at a thickness of about 3 microns. The observed thickness effect can be explained by a fracture mechanics analysis of adhered films where, unlike the case in free films, the energy release rate, G, is independent of crack length but varies with film stress and linearly with film thickness.

The most common structural and dielectric materials for printed wiring boards are polymer composites such as epoxy/fiberglass and polyimide/fiberglass. The light weight, low cost, processability, and low dielectric constant of these materials make them particularly suited for this application.

The polymerization of I-I difluoroethylene has been realized by a non equilibrium plasma at an atmospheric pressure on polymeric substrates such as polypropylene (PP). The graft copolymerizat ion onto the PP film was carried out when activating the polymeric substrate in the presence of argon. The structure of the polymeric film obtained depends on the residual oxygen in the plasma reactor. The role of the radicals which interfere in the grafting mechanisms of monomers onto polypropylene films has been studied.

Laser photoetching of polymers has been shown to be a useful method of producing via holes or patterns and is of potential importance in microelectronics fabrication. The maskless, self-developing nature of the process also offers unique opportunities in the preparation of packaging assemblies. Etching of via holes at any discretionary site for multichip interconnect, for example, provides the circuit designer with additional design flexibility. The photoetching rate is dependent on the absorption coefficient of the polymer (at the laser wavelength) and the irradiating fluence. Further, there appears to be an optimum absorption coefficient to achieve the maximum photoetch rate for a given fluence level. To laser drill holes for interconnects, it is desirable to irradiate at the highest energy (increased rate) possible without damaging underlying metal contact pads.

The chemical nature of the interface formed when an electropositive metal (chromium) is evaporated on the surface of oxygen-containing polymers has been investigated by synchrotron-radiation excited photoemission spectroscopy and by near-edge X-ray absorption fine stnrcture spectroscopy (NEXAFS). PMDA-ODA polyimide was studied along with two polymers intended to more simply model the complex chemical functionality of polyimide. Core-level spectra were resolved into distinct peaks, which were assigned to specific atoms in the polymer units, and changes in the spectra were monitored as chromium metal atoms were evaporated onto the surface. Similarly, NEXAFS spectra were taken as a function of chromium deposition. Results of these experiments show that chromium initially reacts very rapidly with surface carbonyl groups, but less strongly with ether oxygens or arene rings. In all polymers studied, formation of an electron-rich, carbide-like species was observed.

Rapid technological advances in electronic systems technologies are placing increasingly severe demands on interconnection media. One primary driving force is the evolutionary advance in the scale of integration in silicon with its inherent cost and performance advantages. A second key driving force is the revolutionary development of photonics which is rapidly integrating into most levels of the interconnection heirarchy. The performance of large scale electronic systems will be increasingly dominated and limited by their interconnection environment. To sustain the present rate of growth in the performance of future systems, new technology directions in interconnection will be necessary.

This paper will explore the traditional levels of interconnection from IC chip packages to the frame level. It will be shown how the various levels of interconnection interrelate and how all levels must be improved simultaneously to achieve the full performance and cost benefits offered by device advances and photonics. The first major step in this evolution is well underway with the rapid transition to surface mounting of devices. This places new demands on materials and assembly technologies which will be discussed. However, the demands of this first step may eventually appear to be minor compared to those yet to come if current trends continue. Several scenarios for this future will be considered and related to the challenges placed on interconnection technology hardware and materials in terms of performance characteristics such as density, speed and heat dissipation.

Metal-metal interactions have been of vital importance to various technologies, including packaging of electronic materials. Extensive interdiffusion and outdiffusion can lead to undesired alloy formation, and oxide formation on the surface which can hinder subsequent bonding processes. Furthermore, the interactions can be profoundly affected by the ambient gases used, either in the joining process or during subsequent storage and operation. One therefore needs a specially designed metallurgy, a diffusion barrier layer, or a proper ambient to deal with such concerns. The effects of ambient and diffusion barriers on the metal-metal interactions are described. Examples are illustrated where extensive interactions across the diffusion barrier are observed, and their impact on the packaging applications discussed.

Ternary solder alloys have come into wide use in chip bonding, printed circuit board connection, and in ceramic package sealing applications. Little is known concerning phase equilibria in many of these systems. Methods for predicting phase equilibria in the ternary (Pb+Sn)+Ag system using CAD (computer aided design) are described, and a predicted value for the ternary eutectic temperature is compared with values obtained by differential scanning calorimetry (DSC) for this system.

In wetting phenomena surface and interfacial energies play an important part. Due to diffusion, precipitation and adsorption processes these energies are time and temperature dependently changing. The influence on wetting behaviour is investigated using a high resolution wetting balance and metallographic inspection.

Deposition of E-beam interactive films by rf sputtering and their behavior under high intensity irradiation was investigated. Both polycrystalline and amorphous films of SiO2, ZrO2, Al2O3, and Y2O3 were deposited and their behavior under irradiation found to-be strongTy dependent on film structure. Using a modified STEM the formation of small holes (<10nm diam.) was achieved with exposure times in the millisecond range. Deposition parameters, film characteristics, drilling behavior, and a possible mechanism are discussed.

This paper describes a non-conventional route to formation of dense glass-ceramics at relatively low temperatures. Organometallic precursors were used to synthesize powders with controlled purity and stoichiometry in the MgO/A12O3/SiO2 system. These amorphous powders sintered by viscous flow to form a dense glass below 1000°C. Further heating resulted in the formation of very fine grained glass-ceramics. Beta-quartz, cordierite, and cordierite-mullite glass-ceramics were obtained with attractive properties for electronic packaging.

Dielectric properties have been measured for a series of porous and fully densified silica glasses, prepared by the sol-gel technique starting from Si-methoxide or Si-fume. The results for the partially densified glasses do not show any preferred orientation for porosity. When fully densified (˜2.25 gms/cc) without any prior treatment of the gels, they have dielectric constants of ≥ 6.5 and loss factors of 0.002 at 1 MHz, compared to values of 3.8 and <0.001 for commercial fused silica. There is no corresponding anomaly in the d.c. resistivity. Elemental carbon present to the extent of 400–500 ppm is likely to be the main cause for this enhanced dielectric constant. Extensive cleaning of the gels prior to densification to remove this carbon were not completely successful pointing to the difficulty in preparing high purity, low dielectric constant glasses via the organic sol-gel route at least in the bulk form.

Sol-gel processing represents a promising method of fabrication for thin films of electronic ceramics which are useful in a number of packaging and device applications. In this study, the influence of acid and base catalysts on the structure of PbTiO3 gels and films (0.1-1.0μm) was investigated, for the purpose of inducing and identifying gel structures which were the most suitable as precursors for thin dielectric layers. Continuous, crack-free films, with dielectric strengths in excess of 106 V/cm were developed. Basic solutions gelled rapidly, phase separated, and were probably more crosslinked than acidic gels. Acidic gels seemed more capable of polymeric rearrangement during drying, yielding denser amorphous structures with microcrystalline regions. High-field dielectric constants (1 MV/m ac) in the range K=30–40, and K=160–170, were determined for amorphous and crystalline films, respectively.

TiO2 gels are usually obtained through hydrolysis of titanium alkoxides. Chemical additives can however react with the precursor at a molecular level and therefore modify the hydrolysis-condensation reactions. Several examples will be described :acetic acid, acetylacetone or Cr(acac)3. The whole sol-gel process is followed all the way from the precursors to the gel and each step is characterized by spectroscopic experiments (Infra-red, N.M.R, E.S.R.). Some electronic properties of TiO2 gels are then described. Chemical addi-tives allow an optimization of thý sol-gel process according to each speci-fic applications : electrochromic display devices, photoanodes or photoche-mical reactions.

We have studied the densification and dielectric properties of sol-gel derived tantalum oxide thin films as the insulators in MIS capacitors. Hydrolysis of tantalum ethoxide is extremely rapid and goes to completion in ethanol. Condensation is also rapid, and goes to completion in toluene Multiple layers were applied by spin-coating up to thicknesses of 3000 Å before cracking of the coating during drying ensued. Densification occurs from room temperature to 450 C, with the original film thickness decreasing by about half in one hour at 450 C. No additional densification occurs upon heating to 750 C. The dielectric constant decreases from unfired samples to those fired at 450 C, and then increases on firing from 600 to 750 C. The value of the dielectric constant at 1 MHz for samples fired at 750 C for one hour is 20, similar to that of anodically grown Ta2O5. Leakage currents as low as 2 × 10−7 amp cm−2 have been measured for applied fields of 200,000 V cm−1.

Ferroelectric lead zirconate titanate and ferrimagnetic nickel ferrite films were prepared by dip-coating of metal organic solutions. In the amorphous state, both films were porous, with specific porous surface areas on the order of tens of square meters. Crystallization temperatures were in the range of 400 – 500°C. The crystallization kinetics of the porous films and powders of both compounds have been studied by using non-isothermal DSC and isothermal XRD. The kinetic parameters were empirically described by the Johnson-Mehl-Avrami transformation equation α = 1 - exp(-Ktn). The order of reaction (n) of PZT film is approximately 1 but that of the powder is 2, and their activation energies are 80 and 70 kcal/mole, respectively. It was found that the PZT film crystallizes more easily than the powder at the same temperature. The nickel ferrite film and powder, on the other hand, have similar n values ranging from 0.6 to 0.7, with activation energies of 20 and 35 kcal/mole, respectively. The possible mechanisms were also briefly discussed.