High Humidity Test Research Articles

Highly reliable non-conductive adhesives for flip chip CSP applications

Non-conductive adhesives (NCA), widely used in display packaging and fine pitch flip chip packaging technology, have been recommended as one of the most suitable interconnection materials for flip-chip chip size packages (CSPs) due to the advantages such as easier processing, good electrical performance, lower cost, and low temperature processing. Flip chip assembly using modified NCA materials with material property optimization such as CTEs and modulus by loading optimized content of nonconductive fillers for the good electrical, mechanical and reliability characteristics, can enable wide application of NCA materials for fine pitch first level interconnection in the flip chip CSP applications. In this paper, we have developed film type NCA materials for flip chip assembly on organic substrates. NCAs are generally mixture of epoxy polymer resin without any fillers, and have high CTE values un-like conventional underfill materials used to enhance thermal cycling reliability of solder flip chip assembly on organic boards. In order to reduce thermal and mechanical stress and strain induced by CTE mismatch between a chip and organic substrate, the CTE of NCAs was optimized by filler content. The flip chip CSP assembly using modified NCA showed high reliability in various environmental tests, such as thermal cycling test (-55/spl deg/C/+160/spl deg/C, 1000 cycle), high temperature humidity test (85/spl deg/C/85%RH, 1000 h) and high temperature storage test (125/spl deg/C, dry condition). The material properties of NCA such as the curing profile, the thermal expansion, the storage modulus and adhesion were also investigated as a function of filler content.

Controlling Subcritical Crack Growth at Epoxy/Glass Interfaces

The resistance of silane bonded epoxy/glass interfaces to subcritical crack growth was studied as a function of the density of primary bonds between the silane and epoxy using the double-cleavage drilled compression test (DCDC). The silane coupling agents propyltriethoxysilane (PES), 3-aminopropyltriethoxysilane (3-APES) and various mixtures of 3-APES and PES were used to systematically control the bonding density since 3-APES can form primary bonds with both the glass and the epoxy, while PES forms primary bonds only with the glass. The resistance of these interfaces to crack growth was tested under both static and cyclic loading in high and low humidity test environments. These tests allowed the separation of the effects on crack growth due to stress corrosion and cyclic fatigue. Experimental results showed that the density of primary bonding between the silane layer and the epoxy controls the cyclic fatigue resistance of the silanized interfaces. Additionally, for 3-APES bonded epoxy/glass interfaces cyclic fatigue crack growth predominates at both high and low humidities but for PES bonded interfaces, crack growth by stress corrosion dominates at high humidity and by cyclic fatigue at low humidities. For a 50% 3-APES/50% PES bonded interface, stress corrosion effects are somewhat greater than cyclic fatigue effects at high humidities but at low humidities the two effects are comparable. When testing the interfaces for durability, PES bonded interfaces showed spontaneous delamination when aged in distilled water for 36h at 94°C. On the other hand, 3-APES and mixtures of 3-APES bonded interfaces did not show any detrimental effect of the cyclic fatigue resistance when aged in distilled water at temperatures up to 98°C.

Adsorption and Electrothermal Desorption of Hazardous Organic Vapors

In 1997, 6.04 x 10\u8 kg of hazardous air pollutants were emitted into the atmosphere from the United States. A bench-scale activated-carbon fiber-cloth adsorption, electrothermal desorption, and condensation system was designed, built, and operated to demonstrate its ability to capture and recover organic hazardous air pollutants from airstreams. The annular-cartridge configuration of the activated carbon fiber cloth allows low pressure drop and rapid electrothermal regeneration. Adsorption and electrothermal desorption cycling of the system with an airstream containing 1,000 ppmv methyl ethyl ketone (MEK) resulted in closure within 8% by mass. Competitive adsorption between water vapor and MEK reduced MEK adsorption capacity 43% as relative humidity of the gas increased from 4 to 90% at 22°C dry-bulb temperature. Increasing the dry-bulb temperature of the gas stream by 10°C at a constant dew-point temperature resulted in a 37% increase in MEK adsorption compared to the high relative humidity test case, while allowing the water vapor to penetrate the adsorber. The automated system achieves MEK capture efficiency >99.9% by mass while recovering the liquid MEK for reuse.

Effectiveness of conformal coatings on a PBGA subjected to unbiased high humidity, high temperature tests

Plastic ball grid array (PBGA) packages are non‐hermetic surface mount packages, designed in response to market demands for cost‐effective, high I/O count, small footprint, and low profile components. Because of the materials and construction, PBGA packages can be vulnerable to failure mechanisms associated with exposure to temperature and humidity. In some applications, conformal coating has been used as a potential means to mitigate these problems by enhancing moisture ingress resistance. This study focused on the ability of two popular kinds of conformal coatings to protect PBGA packages from moisture‐induced failures. As part of the study, PBGA packages with and without conformal coatings were subjected to moisture ingress, moisture desorption and unbiased high temperature high humidity tests. The principal failure mechanisms observed were delamination and cracking in the packages. Although it was observed that parylene coating did slow down the moisture ingress, the high temperature high humidity tests did not demonstrate that two tested conformal coatings had significant protection against moisture‐induced failures for PBGA packages.

On the Thermal Behavior of Giant Magnetoresistance Heads

The magnetic/mechanical spacing between the transducer and the disk significantly decreases due to thermal expansion of pole tips at stressed high temperature and high humidity tests. The protruded pole tips and alumina overcoat can cause head/disk contacts, resulting in thermal asperities and pole tip damage. The damage at the head–disk interface due to protruded pole tips and alumina overcoat may degrade the drive mechanical performance when flying height is below 10 nm. In this study the change in pole tin recession (PTR) with temperature and current in the writer coil, are measured using an optical profiler and an atomic force microscope for heads having a stack design with single and dual layers of writer coils. The pole tips protrude above the ABS surface by 3–4 nm when the temperature of the head is raised by 50°C. Heads with a single layer of writer coils exhibit significantly lower thermal PTR than those with dual layers of coils. The ABS profiles at elevated temperature generated using the finite element modeling of the differential thermal expansion of various layers in the head stack are in close agreement with the measured profiles. The thermal PTR and alumina overcoat protrusion can be reduced by optimizing the thermal expansion coefficient of the alumina basecoat and overcoat, the height of the head stack, and by replacing alumina by SiO2 and SiC.

Head design considerations for lower thermal pole tip recession and alumina overcoat protrusion

The magnetic/mechanical spacing between the transducer and the disk significantly decreases due to thermal expansion of pole tips at stressed high temperature and high humidity tests. The protruded pole tips and alumina overcoat result increased thermal asperities and can interfere with the higher disc asperities and be damaged due to high contact. The damage at the head-disk interface due to protruded pole tips and alumina overcoat may become a major roadblock in the drive mechanical performance when flying height is below 10 nm. In this study, the thermal PTR defined as change in PTR with temperature is measured using an optical profiler and an AFM for heads having stack design with single and dual layers of writer coil. The pole tips protrude above the ABS surface by 3–4 nm when the temperature of the head is raised by 50°C. Heads with single layer of writer coil exhibit significantly lower thermal PTR than those with dual layers of coils.

Plastic module of laser diode and photodiode mounted on planar lightwave circuit for access network

Low-cost plastic packaging of laser diodes and photodiodes mounted on planar lightwave circuit (PLC) platform are developed and its reliability is confirmed under various environmental and endurance tests. The high performance of the module is maintained under reliability tests, such as high-humidity high-temperature tests (85/spl deg/C, 85%RH) and temperature cycling tests (-40/spl deg/C/85/spl deg/C). No laser diodes show any device characteristics change during environmental tests and their stability has very little dependence on current bias. Although the photodiodes show an increase in leakage current under high-temperature high-humidity tests and the rate of leakage current increase is proportional to the square root of bias voltage, the increase is negligible for system use. These plastic modules can be applied to actual access networks and other fiber-optic networks.

高純度銅原料を用いた銅蒸着膜めっき特性

Dendrite growth and the method of preventing the dendrite growth in nickel electroplating were studied on photochemically etched patterns of vapor depositing copper using a 99.99mass% (4N) copper source.Soft chemical etching and increasing the plating power source ripple were found to be effective in preventing the dendrite growth. No dendrite growth with copper pattern formed using a 6N copper source or rolled or electrodeposited copper foil. It was found that copper patterns formed with a 6N copper source had higher resistivity in high temperature and high humidity testing than patterns formed with a 4N copper source.

The combined effect of speed and humidity on the wear and friction of silicon nitride

A series of ball-on-ring wear tests was performed on sintered silicon nitride. The experiments were carried out to investigate a discrepancy in the literature on the effect of humidity on the wear of silicon nitride. In the experiments reported here, a range of different testing speeds was used and the humidity of the tests held at less than 5% relative humidity (RH), 50% (RH), or 90% (RH). It was found that at the lowest speed that was used, the wear rate at low humidity was higher than that for higher humidity. As the speed increased there was a maximum in the wear rate for the high humidity tests, and a minimum for the low humidity tests, with wear rates for the low humidity tests much lower than for the high humidity tests. At high speeds, the wear rate for the low humidity tests was much lower than that for the high humidity tests. The main mechanism of wear was the tribochemical oxidation of the silicon nitride to form silicon oxide.

Low-loss and stable fiber-to-waveguide connection utilizing UV curable adhesive

A low-loss and stable fiber-to-waveguide connection was realized utilizing a newly developed UV curable epoxy resin which has improved humidity durability. The average connection loss was as low as 0.09 dB/point with a return loss of 46 dB. The loss increase was not observed after a heat-cycle test between -40 and 85 degrees C, a high-temperature test at 85 degrees C, or a low-temperature test at -40 degrees C. In a high-humidity test at 70 degrees C and 90% relative humidity, the loss increase was less than 0.2 dB after 400 h.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reliability Test on One-Side-Recordable Magnetooptical Disks by Block Error Rate Measurement

One-sided magnetooptical (MO) disks of compact-disc size have been evaluated with respect to their reliability by block error rate (BLER) measurement. We have carried out high-temperature and high-humidity tests on our disks. No marked changes in mechanical properties or carrier-to-noise ratio (CNR) after accelerated tests were observed. However, C1 and C2 error count increases were observed. The C2 error count increase indicated increase on large media defect numbers. An Arrhenius plot on the maximum BLER values at elevated temperatures revealed an activation energy of approximately 0.9 eV. Estimated lifetimes of our disks at 31°C are more than 10 years, which means one-sided MO disks have lifetimes as long as two-sided disks, such as the 130-mm MO disk.

A new face down bonding technique using a low melting point metal

A description is given of a face-down bonding technique, the low-melting-point metal connection (LMC) technique, for use in manufacturing liquid-crystal display (LCD) panels. By using a low melting point metal, such as an indium alloy, it is possible to connect the integrated circuit (IC) electrodes and bonding pads on a glass substrate at a temperature lower than 150 degrees C. First, using the dipping method, low-melting-point metal bumps were formed on the IC bonding pads with gold bumps. Shallow-bowl-shaped bumps, 10-20 mu m high, were the result. Next, the IC and the glass substrate were connected at a pressure of 30 gf/bump or less and a temperature of 150 degrees C or less. Two kinds of reliability tests were performed on this sample. One was a thermal shock test (TST): a repetition of -40 and 100 degrees C for 30 min each, for 300 cycles. The other was a high-temperature and high-humidity test: 70 degrees C, 90% relative humidity (RH) for 500 h. In both tests, stable results were obtained. Finally, dot matrix LCD panels, with 640*400 dots, were assembled with 20 driver IC chips. The panels displayed test patterns perfectly. The LMC technique makes it easy to test and repair the IC bonds. The results of the trial manufacturing and testing show that the LMC technique can be readily applied in manufacturing LCD panels and many other kinds of electronic equipment. >

The influence of moisture on surface properties and insulation characteristics of AlN substrates

The influence of moisture on the surface properties and insulation characteristics of sintered aluminum nitride (AlN) substrates was investigated. Two AlN substrates, one nontreated and the other with an oxidizing heat treatment, were exposed to moisture under several sets of conditions. For the nontreated substrate, changes in weight and surface properties were not observed, and neither was degradation of insulation characteristics under high temperature and humidity test conditions (80 degrees C, 90% RH). Under more severe conditions of a pressure cooker test (121 degrees C, 2 atm, water vapor), the surface morphology changed and the insulation characteristics were degraded. These changes are attributed to formation of a new surface layer on the substrate. Verification of this hypothesis was undertaken by carrying out an immersion test in warm water (80 degrees C). Clear changes in surface morphology were seen. Meanwhile, the oxidized substrates were found to experience no changes in weight or surface morphology under the pressure cooker test. It is concluded that the thermal oxidation process is an effective way to protect the AlN substrates against moisture and the subsequent degradation of the insulation characteristics. >

Stability of Screen Printed CdS/CdTe Solar Cells

Some stability studies have been conducted on screen printed CdS/CdTe solar cells. Encapsulated CdS/CdTe modules exhibited excellent stabilities in output performance over 206 days when subjected to outdoor tests under various loading conditions. Accelerated tests were performed on unencapsulated cells. No degradation was observed after 90 days in continuous illumination test, A decrease in conversion efficiency due to an increase in series resistance of the unencapsulated cell took place under high temperature and high humidity tests. It is concluded that the increase in series resistance is caused by a decrease in adhesion between CdTe and C layers, and by swelling of the carbon layer with water absorption. Improved cells showed no degradation in efficiency over periods of 110 days at 100°C and over periods of 28 days at 65°C in 95% relative humidity.

4.3 Vacuum evaporated thin films for solar collectors

Selectively absorbing surfaces are important for the efficient use of solarenergy. The main characteristics aimed at for this type of coatings are the highest possible absorptivity for solar radiation and the lowest possible emissivity for thermal radiation. (Temperatures up to 100–200°C). There are several ways to create surfaces with these properties. In the present work evaporated semiconductor films with suitable anti-reflection coatings were used on different metals. For the laboratory tests, the metals were vacuum evaporated on glass substrates. The evaporations were performed with an electron beam gun in a diffusion pumped system. The evaporated thicknesses and the rate of evaporation were controlled by a quartz crystal monitoring system. The selective coatings were studied on flat and rough metal surfaces. Sinusoidal, metal covered gratings with different periods were used as the rough absorber surfaces. This simplified the measurements of absorptivity and emissivity and gave a more thorough understanding of the basic thin film phenomena. It is possible to use gratings because the general rough surface can be looked upon as a superposition of different sinusoidal gratings. A comparison is made between the properties of the layers on flat and rough surfaces. The coatings were subjected to high humidity and high temperature tests. They were also cycled between the intended working temperature and ambient temperature to check possible degradation. Results concerning film adherence and stability during these environmental tests are given.

Changes of the Eosinophilic Cell Count of Coal Miners Working at High Temperature and High Humidity and Oleesky's Test

Changes of the Eosinophilic Cell Count of Coal Miners Working at High Temperature and High Humidity and Oleesky's Test