Room Temperature Vulcanized Silicone Rubber Research Articles

Fabrication of perforated silicone rubber implant

A technique is described to make perforated RTV silicone rubber implants for tissue augmentation.

Face-Down TAB for Hybrids

Bell Laboratories has for some time been developing tape automated bonding (TAB) techniques for hybrid applications involving medium- and large-scale integrated (MSI/LSI) chips. The present paper describes a face-down TAB approach which results in a structure that resembles a beam lead structure. Process steps required for the fabrication of the face-down TAB structures and physical design requirements to control mechanical failure modes are presented. Detailed information is given in the fabrication of a test structure designed to these requirements. The structure uses gold plated copper tape leads to attach an MSI chip to a thin-film metalized ceramic substrate. The structure is environmentally protected with an room temperature vulcanizing (RTV) silicone rubber encapsulant using the same techniques that are employed for the encapsulation of Bell System hybrids with beam leaded chips. Accelerated temperature cycling tests were carried out using this structure over a range of temperature differentials. The results are encouraging from the standpoint of mechanical reliability for communication applications. The face-down TAB approach is compared to the conventional face-up TAB approach where the back side of the chip is bonded to ceramic substrate on the bases of 1) process steps (with implications for assembly cost), 2) hybrid substrate area requirements, and 3) junction-to-substrate thermal resistance. It was found that the facedown structure appears preferable for hybrid applications where cost and/or area considerations dominate. The face-up structure appears preferable when higher thermal conductivity and/or backside electrical contact are required. It is concluded that for many communication applications the face-down TAB approach can be used to attach MSI/LSI chips to multichip hybrids with size, cost, and reliability benefits analogous to those presently associated with beam leaded chips.

Recent advances in solder bond technology for microelectronic packaging

The recent advances in solder bond technology which have occured in the metallurgical, chemical and mechanical fields for both macroconnections and microconnections have caused a rapid acceleration in the use of solder in microelectronics packaging. Relatively soluble metallurgical coatings can be eroded by solder. This process can be controlled by the appropriate heat treatment, by the judicious choice of solder alloy or by the use of an underlying film (such as nickel) which has a slow dissolution rate in the solder. Intermetallic phase formation between active solder components such as tin and soluble metallizations such as gold and palladium can result in a loss of strength at elevated temperatures. At temperatures below 100°C, extrapolations predict adequate strenght for reasonable lifetimes. Oxidation is the chief chemical problem in soldering; the solution of this problem is approached by acid treatment before soldering and by flux and/or the use of reducing atmospheres during soldering. Corrosion problems after soldering are controlled by encapsulation with materials such as RTV silicone rubber. Mechanical problems dominate the design of joints to surface-mounted components as well as the terminals connecting film integrated circuits to printed-circuit boards. New terminals feature strain relief, insertion limiters, shank stiffeners and optimized solder distributions. Surface mounting is benefiting from novel methods of solder placement and the use of surface tension forces to support the components away from the substrate. The solder post thus created is comparatively insensitive to thermal expansion mismatch and other shear strains and enables the film circuitry to be places under the surface-mounted component. In this technique it is crucial to maintain a high surface tension during soldering to prevent collapse of the posts.

Silicone rubber applied within the eye: a preliminary study

Clear, room temperature vulcanizing silicone rubber (RTV) has already been shown to have well-defined optical and mechanical properties that allow its use as an active optical element. In this work RTV is considered as a possible material for substitution of damaged and/or diseased parts of the human eye, such as the cornea and crystalline lens. The interaction of cured and uncured RTV with eye tissue and eyelike tissue was investigated, and the results support the use of this material in the eye.

Control of Sound Velocity in RTV Silicon Rubber by Compounding Various Powders

Control of Sound Velocity in RTV Silicon Rubber by Compounding Various Powders

New acceleration factors for temperature, humidity, bias testing

New temperature-humidity acceleration factors for surface conductance ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</tex> ) were determined. These can be used to relate device life in a high-stress laboratory environment to device life in a normal-use environment. Analytical expressions for the acceleration factors were derived for both encapsulated and unencapsulated test specimens. Lower acceleration factors were predicted for specimens encapsulated with DC 3-6550 RTV silicone rubber than for unencapsulated specimens. The new acceleration factors were used to predict failure rates due to electrolytic conduction on active devices.

Target strength of spherical reflectors

The homogeneous and Morgan lenses [J. Appl. Phys. 29, 1358 (1958)], 9.0 cm in diameter, are constructed by molding the mixture of RTV silicon rubber and zinc or nylon powder in the form of sphere. The sound velocity of such a composite material is a function of the concentration of the mixture. The materials with a continuous variation of sound velocity cannot be produced for the construction of Morgan lenses. Then an investigation is made of stepped‐index lenses approximated by a number of constant‐index spherical shells. The focusing properties of those lenses are measured for lens diameter to wavelength ratios smaller than 30. Those lenses partially are coated with a pressure release cover. The target‐strength of those reflectors are measured with respect to wavelength and the angle of incidence. Their target‐strength is nearly independent of the angle of incidence and the maximum level is about the same compared to a pressure release plane of equal cross section.

Performance of New Copper Based Metallization Systems in an 85°C 80-Percent RH Cl&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;Contaminated Environment

The performance of TPCNA (Ti-Pd-Cu-Ni-Au) and TCN+A (Ti-CuoNi+Au in selected areas only) meta!lizations in 85°C, 80-percent RH, with 0.5 to 1.8 ppm Cl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was compared with that of the standard TPA (Ti-Pd-Au) metallization. Encapsulated (RTV silicone rubber) and unencapsulated triple track conductor test specimens were used. Electrolytic corrosion was studied by biasing the specimens in the high humidity corrosive environment and measuring in situ leakage currents as a function of time. For the unencapsulated specimens, leakage currents increased and all samples failed by 600 h. The failure rates for TPCNA and TCN+A samples due to the formation of Cu and Ni dendrites between oppositely biased conductors were the same as for TPA which had Au and Pd dentrites. None of the encapsulated samples showed dendrite growth after ~ 1000 h. Unencapsulated TPCNA and TCN+A were less resistant to galvanic corrosion in the moist Cl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> contaminated environment than were the TPA specimens. TCN+A failed first by Ti-Cu delamination and later by delamination of the Au due to corrosive oxidation of the underlying Ni. This latter failure mode was predominant for TPCNA. TPA conductors eventually failed at Ti-Pd interfaces. At 85°C, 80-percent RH, 1.6 ppm C!2, unencapsulated TCN+A degraded at the Ti-Cu interface ~10 times faster than unencapsulated TPA at the Ti-Pd interface. The corrosion product found on unencapsulated TPCNA and TCN+A and on Cu-NiAu external leads was identified as Cu, NiCl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . 3 [Cu, Ni(OH) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ]. The encapsulant was extremely effective in retarding galvanic corrosion. For encapsulated TCN+A and TPCNA, eventual bond failures were the result of penetration of the corrosive environment under the edges of the encapsulant. For TCN+A, encapsulation retarded the time to failure by a factor of >10. The relative resistance to galvanic corrosion in moist Cl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> may be ranked TPA > TPCNA > TCN+A.

Room temperature vulcanizing silicone rubber as an optical element

Room temperature vulcanizing silicone rubber as an optical element

Light-weight RTV silicone for maxillofacial prostheses

Weight is a problem in retention of large skin-textured maxillofacial prostheses. The purpose of this investigation was to test the feasibility of mixing foam RTV silicone rubber with conventional RTV silicone rubber to obtain a light-weight material. Various mixtures of foam and conventional silicone rubber were formulated and tested for strength, accuracy of molding, color application, color stability, and texture. A special flask to support the mold was necessary in order to overcome expansion problems associated with gas formation of the foam silicone rubber. The mold required venting to release the gas and to reduce the expansion of the prosthesis in order to maintain accuracy. Molding, accuracy, texture, and color problems were overcome. Reduction of weight proportionate to reduction of tear strength of the material formulated, however, did not allow routine use of mixtures of foam and conventional silicone. When the weight of a prosthesis is critical and excessive and thickness is sufficient to give adequate strength, the foam and conventional silicone mixture can be used.

Bias-Humidity Performance of Encapsulated and Unencapsulated Ti-Pd-Au Thin-Film Conductors in an Environment Contaminated with Cl&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;

Both encapsulated and unencapsulated Ti-Pd-Au thin-film conductors on AI <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> substrates were biased in an 85°C 80-percent RH environment contaminated with Cl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . The encapsulant was an RTV silicone rubber. During exposure to the corrosive environment, leakage currents between adjacent conductors were periodically measured and recorded. Leakage currents for the unencapsulated specimens increased with time, and many were shorted after approximately 400 h. In contrast to this behavior, there were no increases in leakage currents for the silicone rubber encapsulated conductors. At the end of the test, selected specimens were examined using a light microscope and an SEM with X-ray capability. No metal migration was observed on the encapsulated samples. The unencapsulated conductors showed dendritic growth between the electrodes; X-ray analysis showed the growths to consist of both Au and Pd. It is concluded that the RTV silicone encapsulant effectively prevents high leakage currents and subsequent metal migration on biased Ti-Pd-Au conductor specimens exposed to a moist Cl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> environment. Unencapsulated samples are rapidly degraded under the same conditions with the main failure mechanism being metal migration.

Encapsulation of Integrated Circuits Containing Beam Leaded Devices with a Silicone RTV Dispersion

This paper reviews the results of a number of investigations which have been performed to evaluate the use of an RTV silicone rubber dispersion for the encapsulation (conformal coating) of integrated circuits containing beam leaded silicon integrated circuit (SIC) devices. The dispersion consists of approximately 67-percent xylene and 33-percent solids by weight. The investigations described include: 1 ) measurement techniques for and typical values of the properties of the as-received dispersion and of the material after curing; 2) the determination of the suitability of the dispersion to be applied to integrated circuits containing SlC's by a flowcoat technique, and of its capability to completely fill under SlC's after curing; and 3) the performance of encapsulated test specimens and circuits in some initial accelerated bias-humidity and temperature cycling tests. In addition, several other factors relevant to determining the suitability of the dispersion for particular circuit applications are briefly dis- cussed.

Speed of sound and transmission loss in silicone rubbers at ultrasonic frequencies

The speed of sound as a function of temperature (0°–3°C) and the transmission loss in 2.5-cm-thick samples of 13 different RTV silicone rubbers have been measured in the frequency range 500 kHz–1 MHz. The range of measured sound speeds for the various materials was between 960 and 1110 m/sec at 0°C. The thermal coefficients of sound speed were approximately −3 m/sec °C for all samples. The transmission losses ranged from near 0 dB for RTV-602 to 14 dB for RTV-90 at 1 MHz.

Bondability of RTV Silicone Rubber

Glow discharge method for producing a bondable Room Temperature Vulcanizing (RTV) silicone is described. Mechanical and chemical properties of silicone specimens are described. Theory concerning the relationship between surface characteristics and bondability is examined with respect to the polymer specimen.

The Chemistry and Properties of the Medical-Grade Silicones

Abstract The medical grade silicones are probably the most widely used of all the synthetic polymers for permanently implanted subdermal devices. This paper reviews the chemistry of these materials from the original polymer manufacturing through the various stages necessary to obtain the types of heat vulcanizing silicone rubber, room temperature vulcanizing silicone rubber, and silicone rubber adhesive most commonly used in medical applications.

Techniques of Making Plastic Casts of Artifacts from Permanent Molds

AbstractA method for making duplicates of projectile points or other ethnic artifacts is presented. A two-piece mold of RTV silicone rubber is made over the object. Cold-cure acrylic, colored with dry pigment, is incorporated in the mold to produce a replica of the original artifact, in both color and texture.

A new solution for the skin-friction drag on a cylinder.

range of 1.92 to 0.44 and values obtained from the upper deceleration curve by using CDS = F/q agree fairly well with the contraves tracking camera trajectory data. The decay in dynamic pressure with time from launch for test 158-13 is shown in Fig. 4. The sharp trajectory alteration at parachute deployment is graphically illustrated in Fig. 5 as obtained from the Contraves Cine theodolites.3 Two coats of RTV silicone rubber cement were applied to the guide surface pilot chute and the suspension lines of the 20-ft chute on all three tests to act as an ablator for the aerodynamic heating resulting from the approximate 500 °F stagnation temperature. Conclusions A series of three Nike/Nike rocket-boosted tests of a specially designed 20-ft-diam ribbon parachute has been conducted. It is concluded that 1) the chute is suitable for use up to M = 2.43 and a dynamic pressure of 5700 psf using a 1100-lb total weight test vehicle system and 2) both the 18-in.diam pilot chute and reefed main 20-ft chute operated in a stable configuration and without damage during deployment.

Experiments with injectable plastic: Use of silicone and silastic rubber in animals and its clinical use in deformities of the head and neck

In summary, silicone fluid, solid RTV Silastic silicone rubber, and gel-like mixtures of the two were individually studied and found to provoke similar host-tissue responses in the liquid, solid, and gel states. The sole exception was a variable diminution in the residual amount of the fluid silicone injected. Each variation after injection showed physical properties quite similar to the bony and soft tissues present around the head and neck; that is, the RTV silicone rubber could blend quite easily with bony and hard muscle contours, the silicone-rubber-Silastic fluid mixtures were not dissimilar from muscle and glandular tissue, and the fluid silicone, after injection, blended extremely well with the soft subcutaneous areas. Since the Federal Food and Drug Administration has listed the injectable silicone fluid and RTV Silastic materials as drugs rather than prostheses, injection of these materials in humans has been halted in this clinic. This has seriously hampered the study and use in the clinical correction of deformities of the head and neck such as defects of the calvarium, forehead, and malar and mandibular regions, as well as the correction of extensive tissue deformities after hemiatrophy of the face, the removal of large deep tumors, severe surgical losses of tissue, and the correction of late enophthalmos. In view of the microscopic findings presented it is hoped that the F.D.A. will soon release this new drug to a more extensive clinical investigation.