Synthesis and Application of Ceramic Paste for High-Temperature Electronic Packaging

This dissertation research focused on the synthesis and application of ceramic paste for high-temperature applications. An alumina paste material comprising aluminum dihydric phosphate and alumina powder was developed for high-temperature electronic packaging. Nano aluminum nitride and nano-silica powders were embedded to promote the paste curing process, limit the grain growth, and increase its bond shear strength. The chip-to-substrate bond strength was enhanced and met the MIL-STD requirements for die-attach assembly. Its encapsulation property was improved with fewer cracks compared to similar commercial ceramic encapsulants. The die-attach material and encapsulation properties tested at 500°C showed no defect or additional cracks. Thermal aging and thermal cycling were carried out on the synthesized paste. XPS analysis revealed a higher oxygen bonding percentage for the 10% nanosilica ceramic sample than other samples. XRD peak broadening is largest for the 10% nano-silica ceramic which indicated smaller crystallite sizes. The smaller crystallite size for the 10% nanosilica sample introduces a larger microstrain to the alumina crystal structure. FTIR revealed the presence of alumina-silicate bonds on these samples with the largest amount present in the 10% nanosilica samples. SEM and EDX results showed a uniform bond line for the 10% sample and uniform material distribution. An electronic packaging technology that survives the Venusian condition was developed. Alumina ceramic substrates and gold conductors on alumina were evaluated for electrical and mechanical performance. The most promising die-attach materials were found to be thick-film gold and alumina-based ceramic pastes. Alumina, sapphire, silicon, and silicon carbide dice were attached to the alumina substrates using these die-attach materials and exposed to the Venusian condition for 244 hours. The devices on the packaging substrates were encapsulated by a ceramic encapsulant with no significant increase in cracks and voids after the Venusian simulator test. Wire pull strength tests were conducted on the gold bond wire to evaluate mechanical durability before and after the Venusian simulator exposure test with about 30.8% decrease which satisfied the minimum requirement for the MIL-STD-885 method. The overall wire-bond daisy-chain resistance change was 0.47% after the Venus simulator test, indicating a promising wire bond integrity. A titanium package was fabricated to house the ceramic packaging substrate and a two-level metalized feedthrough was fabricated to provide electrical interfaces to the package. A double-layer ceramic electronic packaging technology that survives the Venusian surface condition was developed using a ceramic interlayer dielectric with gold conductors. A 60-µm ceramic interlayer dielectric served as the insulator between the top and bottom gold conductors on high-purity ceramic substrates. Test devices with AuPtPd metallization were attached to the top gold pads using a thick-film gold paste. Thermal aging for 115 hours at 500°C and thermal cycling from room temperature to 450°C were performed. Dielectric leakage tests of the interlayer ceramic layer between the top and bottom gold conductors revealed a leakage current density of less than 50 10-7 A/cm2 at 600V after thermal cycling. The die shear test showed a 33% decrease in die shear strength after thermal tests but still satisfies the MIL-STD method

LTCC packaging for Lab-on-a-chip application

LTCC -pakkaus Lab-on-a-chip -sovellukseen. Tiivistelmä. Tässä työssä suunniteltiin, valmistettiin ja testattiin uusi pakkaustekniikka ”Lab-on-a-chip” (LOC) -sovellukseen. Pakkaus tehtiin pii-mikrosirulle, jolla voidaan mitata solujen kiinnittymistä sirun pintaan solujen elinkelpoisuuden indikaattorina. Luotettavuustestaukset tehtiin daisy-chain -resistanssimittauksilla solunkasvatusolosuhteissa. Lisäksi työssä selvitettiin LTCC- ja ”Lab-on-a-chip” -teknologioiden perusteet teoreettiselta pohjalta. Mikrosirun pakkauksessa käytettiin joustavaa LTCC-teknologiaa. Sähköisiin kontakteihin ja niiden suojauksiin käytettiin sekä johtavia että eristäviä epoksi-liimoja. LOC-sovelluksiin on tärkeää kehittää uusia pakkausmenetelmiä jotta näiden laitteiden kaikki ominaisuudet saadaan toimimaan luotettavasti. Pakkaus testattiin samoissa olosuhteissa missä sitä tullaan käyttämään ja pakkaus kesti kaikki nämä haasteet. Lisäksi esitetty valmistusprosessi on sellainen, että sitä voidaan käyttää myös muihin ”Lab-on-a-chip” -sovelluksiin.Abstract. This work presents design, manufacturing and testing of new packaging method for Lab-on-a-chip (LOC) application. Packaging was made for silicon microchip which can measure cell adhesion on chips surface as indication of cell viability. Reliability testing was done with daisy-chain resistance measurement in real conditions. Moreover basic theory of LTCC and Lab-on-a-chip technology is presented. Resilient LTCC technology was used for packaging material and conductive/insulating epoxies were applied for electrical contacts and barriers against the environment. It is fundamentally important to develop new packaging methods for LOC applications, so all the properties can be utilized reliably. Packaging was tested under the cell growth conditions and the package showed to withstand all these challenges. Moreover the presented packaging method is possible to use also in other Lab-on-a-chip applications

Space station power semiconductor package

A package of high-power switching semiconductors for the space station have been designed and fabricated. The package includes a high-voltage (600 volts) high current (50 amps) NPN Fast Switching Power Transistor and a high-voltage (1200 volts), high-current (50 amps) Fast Recovery Diode. The package features an isolated collector for the transistors and an isolated anode for the diode. Beryllia is used as the isolation material resulting in a thermal resistance for both devices of .2 degrees per watt. Additional features include a hermetical seal for long life -- greater than 10 years in a space environment. Also, the package design resulted in a low electrical energy loss with the reduction of eddy currents, stray inductances, circuit inductance, and capacitance. The required package design and device parameters have been achieved. Test results for the transistor and diode utilizing the space station package is given

Diode laser modules based on laser-machined, multi-layer ceramic substrates with integrated water cooling and micro-optics

This thesis presents a study on the use of low temperature co-fired ceramic (LTCC) material as a new platform for the packaging of multiple broad area single emitter diode lasers. This will address the recent trend in the laser industry of combining multiple laser diodes in a common package to reach the beam brightness and power required for pumping fibre lasers and for direct-diode industrial applications, such as welding, cutting, and etching. Packages based on multiple single emitters offer advantages over those derived from monolithic diode bars such as higher brightness, negligible thermal crosstalk between neighbouring emitters and protection against cascading failed emitters. In addition, insulated sub-mounted laser diodes based on telecommunication standards are preferred to diode bars and stacks because of the degree of assembly automation, and improved lifetime. At present, lasers are packaged on Cu or CuW platforms, whose high thermal conductivities allow an efficient passive cooling. However, as the number of emitters per package increases and improvements in the laser technology enable higher output power, the passive cooling will become insufficient. To overcome this problem, a LTCC platform capable of actively removing the heat generated by the lasers through impingement jet cooling was developed. It was provided with an internal water manifold capable to impinge water at 0.15 lmin-1 flow rate on the back surface of each laser with a variation of less than 2 °C in the temperature between the diodes. The thermal impedance of 2.7°C/W obtained allows the LTCC structure to cool the latest commercial broad area single emitter diode lasers which deliver up to 13 W of optical power. Commonly, the emitters are placed in a “staircase” formation to stack the emitters in the fast-axis, maintaining the brightness of the diode lasers. However, due to technical difficulties of machining the LTCC structure with a staircase-shaped face, a novel out-plane beam shaping method was proposed to obtain an elegant and compact free space combination of the laser beam on board using inexpensive optics. A compact arrangement was obtained using aligned folding mirrors, which stacked the beams on top of each other in the fast direction with the minimum dead space

Study to develop process controls for line certification on hybrid microcircuits Final report, Nov. 1970 - Feb. 1971

Basic process steps for fabrication of thick or thin film microcircuits for NASA us

Wire-bonds Durability in High-temperature Applications

This work aims to determine the suitability of use of low-temperature co-fired ceramics (LTCC) and thi ck film technology in applications with semiconductors base d on SiC and GaN, which have high operating tempera ture. Especially, Heraeus HeraLock 2000 substrate is inve stigated. The paper is mainly focused on the behavi our and reliability of wire-bonds, which are used for conne ction of the above-mentioned semiconducting devices with a circuit or a package. A test sample was designed for this purpose, which was subjected to thermal lo ad. Subsequently, changes in the bonds resistivity were studied, together with their strength and any defe cts caused by the thermal load. Other properties, such as term omechanical stress of the material for different te mperature profiles were simulated in the ANSYS software. Crea ted mathematical model simulated and compared differences between gold and aluminium wire-bond

Review of LTCC technology for millimeter waves and photonics

VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields

Review of LTCC technology for millimeter waves and photonics

VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields

Review of LTCC Technology for Millimeter Waves and Photonics

VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields