Development of large thick-film multilayers assemblies

WORLD

ABSTRACTS

ON MICROELECTRONICS

evidence sgsinst the effiistence o f such states in these noa-Omsy disordered materials is overwhelming. T h e pm~dox is resolved by noting that if the material is in

AND RELIABILITY

27

thermodynamic equilibrium, the disorder of the atomic potentials will not result in disorder of the valence or conduction band energy levels.

8. THICK- AND T H I N - I q L M COMPONENTS, CIRCUITS AND MATERIALS D e v e l o p m m U of large ussembl/mk H. R. I ~ ,

tidck4Um muitilayors J. W. K a ~ and E. G.

B~SmACKL IEEE

Parts,

Tram.

Hybrids

Packng

]PHP4, No. 2 (1972), p. 20. A recent sophisticated aerospace vehicle required advanced electronic packaging design to meet the stringent space and weight requirements imposed on the electronics system. Thick-film assemblies using screen printed multilayer interconnnection boards were chosen to meet this need. T o reduce errors and decrease turnaround time, computer-aided artwork generation was used. The multilayer structure consisted of alternating layers of conductor and dielectric materials on a 4 × 6 × 0"025 in. alumina substrate. T h e complexity of the boards ranged from two to five conductor layers with some boards requiring feedthrough holes to make connection to a ground plane on the back side. T h e multiiayer fabrication process generally followed standard thick-film procedures with few variations. Substrate warpage and screen printing problems were encountered in scaling up the process from 2 × 2 in. to 4 × 6in. substrates. In general, more variation in print thickness was encountered and less variation in process control could be tolerated for a large substrate. The thick-film multilayer assembly was completed by bonding the substrate to a heat sink, and reflow and hand soldering the discrete components and thick-film subassemblies to the multilayer board. Stability o f n l c k e l - c h r o m i u m thin f i l m resistors.

J. AHeRN and K. Hmv. IEEE Trans. Parts, Hybrids Packng PHP-8, No. 2 (1972), p. I0. This study explores the major factors which may affect the stability of thin film nickel-chromium resistors. These factors include annealing temperatures, manufacturing processes, form factors, power density and trimming. The results of a 1000-hr load life study are given in terms of these same major factors. A n analysis of voltage bias stressing c h a r a c t e r i s t i c s o f t a n t a l u m thin f i l m capacitor. M. NAKAMU~, J. YAMAZAKI,W. ENDOU, Y. NISHIMURA. Trans. Inst. Electron. Commun. Engrs. Japan 55C, No. 4 (1972), p. 207. (In Japanese.) The characteristics of tantalum thin film capacitors prepared by sputtering method depend on the condition of preparation. The T C C is found to be directly proportional to tan 8, and is inversely proportional to the insulation resistance. This paper reports the [1-/ characteristics and the bias voltage depemtence of the capacitance of the capacitor. From e~perimental results, it is likely that the densi W of donors (the sub-oxide of tantalum or other impurities) influences T C C , tan 8 and insulation resistance of the capacitor. Then, the relation between the T C C and tan 8 or the T C C and the insulation resistance is explicable.

B o n d e d c r o s s o v e r s f o r t h l , f i l m circuits. J. A, BURNS. IEEE Trans. Parts, Hybrids Paclmg P H I l , No. 2 (1972), p. 35. A method is presented for batch fabricating on a polyimide film an array of crossovers for a thin film circuit. T h e crossovers are subsequently transferred to the thin film substrate by a batch bonding technique which forms gold-to-gold solid state bonds at the ends of each crossover span. The resulting structure is a free standing arch which is subsequently encapsulated for mechanical and environmental protection. This paper describes the crossover fabrication sequence, the bonding operation, results to date, and a disctmsion of the basic advantages of the approach. H o p p l n g - c o n d u c t i o n in ( ~ Cr a m o r p h o u s thin films. H. DAy.n, O. MASSmq~Tand B. K. CHAK~VSm~. Solid St. Commun. 11 (1972), p. 131. Thin amorphous films of germanium and of G e - C r alloys have been p r e p a i d by vacuum evaporation. Their electrical resistiVity is stddied in function of temperature for concentrations of chromium up to 13.5 per cent. The results are analysed and compared to Mott and Ambegaokar theories of electrical conduction in amorphous materials. H i g h staMllty c o s p u t t e r e d Ta-50 at. % AI alloy f i l m resistors. F. HuBm~ and D. J ~ . IEEE Trans. Parts, Hybrids Paclcng PHP-8, No. 2 (1972), p. 4. The potential of sputtered Ta-50 at. % AI alloy films for tantalum integrated circuit resistor applicetions was evaluated. Test resistors covering a range of 25-1000 r~/[] were fabricated from 900 to 1500 A thick alloy films (on ceramic substrates) using two different anodic thinning-stab/I/zation heat treatment process sequences. The effect of initial thickness and process sequence on stability was determined by accelerated aging, thermally at 250 and lS0°C, and under d.c. power at 2 W (6"2 W/cml). It was found that the Ta-50 at. % Al alloys offer outstanding potential for circuit and R - C network applications requiring highly stable 25-1000 ~/[~ film resistors. For such applications, the alloys exhibit a combination of attractive characteristics which include: (1) the ability to readily adjust the sheet resistance by anodization; (2) the maintenance of a relatively constant temperature coefficient of resistance; (3) excellent stability during both thermal and power aging tests. Sputtered layers featuring high area resistance a n d l o w t e m p e r a t u r e coefficient. J. MmovsxY. T E S L A Electron. 2/72, p. 52. Resistive layers with an area resistance up to 50 k• and a temperature coe~cient better than __.50 × 10-s/°C have been obtained by reactive sputtering of tantalum and a NiCr alloy, the components ratio of which was 80% Ni: 20% Cr; the