Microelectronics International

Svetkoff, D.J.; Smith, D.N.; Doss, B.L.

1987 Microelectronics International

doi: 10.1108/eb044268

Recently great interest has developed for a high speed, flexible machine vision system which can accurately determine solder paste and component placement for both process verification and quality control inspection. Present SMT inspection systems must cope with the unpredictable appearance of components and backgrounds and are often used only to determine presence and absence. This paper describes a new approach which combines greyscale data with a threedimensional map of the board under test. Originally this method was proposed as a robust technique for locating components in low contrast greyscale images. However, experience working with manufacturers and developers of placement equipment has shown that emerging SMT inspection requirements indicate the importance of threedimensional information. In addition to the detection of components and measurement of orientation, examples are shown of solder paste volume measurements, lead coplanarity, and tombstone effect detection.

Klein Wassink, R.J.

1987 Microelectronics International

doi: 10.1108/eb044269

Some characteristics of the metallisation of leadless ceramic components are discussed, such as dissolution, reliability of joints, intermetallic compound formations and the migration of silver. It is concluded that it is not the type of the metallisation that is important, but the quality of the make.

Palanisamy, P.; Sarma, D.H.R.

1987 Microelectronics International

doi: 10.1108/eb044270

A major drawback of current copper thickfilm technology is the inefficient removal of the organic binder associated with the dielectric material in the lowoxygen inert gas N2 atmosphere of the furnace. In processing large area andor multilayer substrates, the incomplete binder removal causes deleterious effects which have been well documented. Therefore, it is necessary to remove hydrocarbons and residual carbon from the films in the burnout section of the furnace before the films begin developing their characteristic microstructures. However, the atmosphere currently employed is not capable of removing all the carbon and hydrogen in the form of gaseous oxides. In literature, in addition to furnace modifications, several atmosphere modifications and manipulations have been proposed to achieve optimum properties for the fired films. With few exceptions, the scientific basis for such atmosphere modifications and manipulations has been left either unaddressed or obscure. With this background, this paper examines the feasibility of using a reactive gas mixture in the furnace to achieve efficient organic binder removal. Phase stability diagrams are presented to illustrate the stability of i carbon, ii thick film copper ingredients, iii active phases of resistors, and iv components of glassy and crystalline phases of dielectrics in selected reactive atmospheres. The stability of certain furnace belt constituents is also addressed. Mass balance calculations are shown to demonstrate the extent of carbon removal and copper oxidation in typical nitrogen atmospheres. Based on the interpretation of thermodynamic data and reaction mechanisms involved, a specific H2H2O mixture with nitrogen as the carrier gas is recommended. The approach presented here constitutes a general analytical scheme to understand materialsatmosphere interactions occurring across a temperature range. Several issues in furnace design are also discussed from the standpoint of gassolid reaction kinetics. These deal with the design of gasflow systems that facilitate removal of organic binders.

Herod, B.; LusniakWojcicka, D.

1987 Microelectronics International

doi: 10.1108/eb044271

Manufacturing of thin film potentiometers involves using very special substrates, usually with complicated shapes and explicit dimensional tolerance. Commonly, such substrates should possess holes and recesses for assembling of the terminals as well as for mounting into housing. Particular difficulties are connected with the labour and time consumption necessary for forming of the molten glass, and limited utilisation of the glass substrates for potentiometer bodies. On the other hand, this material is the best one for the thin film elements. To solve these problems with the objective of producing inexpensive glass substrates for potentiometers, different tests were carried out with moulded elements made from glass powder. The aim of this research was the optimisation of a glass frit granulation and composition of the softening agent plasticiser as well as a choice of the temperature profile of firing of the moulded pieces to guarantee the precise structure of the substrate, essential for its application in thin film technology.

Davey, N.M.; Wiese, F.W.

1987 Microelectronics International

doi: 10.1108/eb044272

Silverglass die attach materials represent a significant advance in silicon packaging technology and are expected to displace goldsilicon eutectic bonding as the preferred method of die attachment for high reliability applications. In this paper the rle of the glass in the adhesion mechanism of silverglass to gold and chromiumgold backed die has been determined using thermal analysis and Xray diffraction in addition to scanning electron microscopy and electron probe microanalysis of the sintered film. An adhesion mechanism is proposed in which the glass of the silverglass system migrates to the die interface during the firing cycle and chemically bonds to the silicon which is present at the surface of the goldsilicon eutectic. Adhesion between the die back and the silver of the die attach material is by means of a simple mechanical bond between fingers of glass and the sintered silver matrix. Thermodynamic and kinetic considerations suggest that insufficient silicon dioxide may be formed using chromiumgold backed die for acceptable adhesion. Processing changes are proposed which resolve this adhesion problem.

Storbeck, I.; Leitner, G.

1987 Microelectronics International

doi: 10.1108/eb044273

The bowing of thick film substrates, wholly covered with copper pastes of the Du Pont base metal system DP 9922 and 9924, with one, four and ten layers has been measured from room temperature up to 700C. It could be shown that the bowing does not, as expected, decrease uniformly with increasing temperature up to the softening point of the glass, but a change occurs in the curvature of bowing between about 80 and 100C. By removing the copper layers the glassy interlayer could be investigated on the substrate. Its temperature behaviour is quite linear up to the softening point and the curvature is in contrast to that of the complete copper layer on the substrate. The superposition of the curvature of the metal and the glassy interlayer leads to the abovementioned change in the curvature of the complete copper layer. The deviation of the bowing that was found experimentally and that calculated by means of the plates theory, discussed in a previous paper, can therefore be explained by that change in the curvature and by a plastic deformation process in the copper. The values are caused by a reduction of stresses by plastic deformation in the metal during the cooling process. These results offer some possibilities for a reduction of the bowing of multilayer interconnection modules for use in hybrid microelectronics.

Anderson, S.; St Jean, J.

1987 Microelectronics International

doi: 10.1108/eb044274

A packaging system has been developed using surface mounted components on ceramic substrates for conductivecooling applications. This has resulted in a high density, high reliability, and highly producible product. A 20 squareinch module can mount up to 150 leadless chip carriers and can dissipate up to 30 W with a maximum junction temperature Tj of 90C. Design guidelines, processing, and assembly techniques geared to surface mount devices for this high density ceramic thickfilm multilayer interconnect board will be presented. Constraints regarding the thermal characteristics and physical dimensions of the devices and the limitations of CAD routers, processing equipment, and automatic assembly equipment will also be discussed. Design guidelines regarding the electrical characteristics, such as capacitance and resistance in terms of layout and processing, will be defined. Timing criticality and busing layout guidelines will be discussed. Processing design considerations such as power and ground planes, conductor layers, layout boundaries, and surface mount footprints will be outlined. Other considerations taken during the placement, routing, and artwork phases will be presented, as well as those items to be considered during the processing flow. The assembly process will be discussed emphasising problems that can be encountered with tinning, placement, reflow, and cleaning. Rework of defective surface mount components will be reviewed in addition to considerations for design modifications.

Shook, R.L.

1987 Microelectronics International

doi: 10.1108/eb044275

A study was undertaken to evaluate the thermosonic goldwire bonding capability to TiPdCuNiAu thin film metallisation on newly developed polymer hybrid integrated circuits POLYHICs. The POLYHIC technology incorporates alternating layers of polymer and metal added to conventional Hybrid Integrated Circuits which provide for increased interconnection density. Destructive wirepull strengths were measured as a function of varying wirebonding machine operating parameters of wedge bond force, wedge bond time, temperature, and ultrasonic energy. All data were evaluated and compared with wire bonding under similar conditions to thin film circuits on Al2O3 ceramic. The results for wedgebond associated failures indicated that machine operating parameters of wedge bond force, time and ultrasonic energy similarly affected the average wirepull strength for both the ceramic and POLYHIC circuits. Pull strengths for equivalent metallisation schemes and bonding parameters were generally slightly higher and more tightly distributed for bonds made to metal films on ceramic. A strong correlation was found to exist between wirepull strengths and surface topography as measured by a profilometer technique of the thin film metallisation for the POLYHICs which had both smooth and rough metallisation surfaces for metal films on top of the polymer. The results indicated that rough metallisation bonded more easily and yielded much higher wirepull strengths. Also, rougher films were shown to effectively increase the parameteroperating windows for producing reliable wire bonds. A semiquantitative analysis was developed to help explain this correlation. Surface topography effects were also found to be a key factor when evaluating wire bondability as a function of substrate bonding temperature. Wedgebond strength was essentially independent of temperature for bonds made to rougher metallisation while a strong temperature dependency was found when wire bonds were made to smoother films.

Hughes, J.E.

1987 Microelectronics International

doi: 10.1108/eb044276

This paper will be presented in two parts. Part 1, after an introduction to thin film resistor technology, gives a review of thin films and other resistors, followed by designer's considerations when using resistors and networks. Part 2 will deal with assembly problems.

Fitt, J.; Reimann, J.; Thust, H.

1987 Microelectronics International

doi: 10.1108/eb044277

Microwave and thermal problems in manufacturing highpower microwave attenuators are considered and some proposals of thick film solutions are presented. Theoretical considerations have been confronted with the results of measurements.

Clatterbaugh, G.; Charles, H.K.

1987 Microelectronics International

doi: 10.1108/eb044279

Numerical techniques and experimental methods for the electrical characterisation and design of large multilayer thick film circuit boards are discussed. The numerical techniques investigated here include the boundary element and finite element methods for the estimation of capacitance and inductance and the method of normal modes for the analysis of voltage crosstalk between coupled transmission lines. Threedimensional capacitance and inductance calculations are included for typical thick film signal line and power and ground grid plane configurations. Numerical results are compared with measured data obtained from carefully constructed test coupons. Electrical characteristics of several popular high speed logic families and their compatibility with multilayer thick film interconnects are discussed and guidelines for the design of large thick film circuit boards for high speed digital applications are presented.

Sinnadurai, Nihal

1987 Microelectronics International

doi: 10.1108/eb044278

The once highly publicised Porcelain Enamelled Steel PES substrates seem to have disappeared from the public gaze, or have they They certainly have not. If anything, they have consolidated their place in electronics applications and are growing in use at a remarkable pace in particular applications supplied by the major USA source, namely FerroECA.

1987 Microelectronics International

doi: 10.1108/eb044280

A narration of the fascinating history of the Du Pont Company could almost fill volumes and it would be temptingly easy to utilise the journalistic clich that here space does not permit an indepth documentation of the company's development and multifaceted diversification. However, for those unaware of the origins of this giant organisation's activities, a brief summary would take us back to 1799, in the wake of the French Revolution, when a French family set sail for America on the American Eagle, with aspirations to establish a colony in Virginia. This aim did not materialise, but in 1802 one of the sons, Eleuthre Irne du Pont de Nemours, a former chemistry student of Lavoisier, formed his company on a piece of land along the banks of the Brandywine River near Wilmington, Delaware.

1987 Microelectronics International

doi: 10.1108/eb044281

The ISHMBenelux Chapter will organise a oneday conference at the Antwerp Crest Hotel, on Thursday 29 October 1987. The conference will be aimed at applications of hybrid circuits rather than technology.

1987 Microelectronics International

doi: 10.1108/eb044282

Mr Peter Knight has joined Balzers High Vacuum Ltd, Berkhamsted, as sales engineer, thin films. Responsible to thin films manager Jim Rees, he will handle all UK sales of specific Balzers thin film products. These include chip resistors, daylight conversion filters, dichroic illumination filters, Calflex heat protection filters, as well as Contraflex antiglare panels and large area antireflection coatings.

1987 Microelectronics International

doi: 10.1108/eb044283

A new high precision reflow solderingbonding machine, the Farco F130, ideal for automatically placing and accurately soldering surface mount devices such as flatpacks, chip carriers, SO and VSO components is available from Dage. TAB Tape Automated Bonding components can also be processed using the F130's modular system design which allows the machine to be more versatile in application.