Systems for Large Thick Film Substrates Large Area Precision Screen Printer BFI Electronics Limited have introduced a large-area precision A new range of feed systems is claimed to be particularly suitable screen printer specifically for the electronics industry. It is claimed to for larger substrates and those with special flatness problems. The be the first of its size capable of the registration, repeatability, DEK AUTOFEED 3960/3970/3980 series, can be used with a number material deposition control and operating parameter tolerances of process machines in the manufacture of thick film circuits and normally associated with very precise thick film applications. related components such as miniature switches and potentiometers, up The AMI/Presco Model 2405 operates under electronic control and to a maximum size of 102 x 102 mm. accepts screen frames up to 36 in x 36 in overall, printing an area up to The handling techniques include vacuum pick-off heads and 24 in x 24 in. The system has motorised controls with digital readouts walking beam mechanisms. The heads unload and reload magazines for X, Y and snap-off screen positioning. and remove substrates from dryer or furnace belts. Substrates are The squeegee drive is fully hydraulic with travel limits, active print moved between these points by the walking beams, fingers on the stroke length, and each direction of squeegee stroke is independently beams keeping the substrates separated from one another as they are adjustable. A semi-contact print feature is included wherein the screen indexed along step by step in synchronism with the process machine. frame trailing edge can be made to lift an adjustable amount during This protective feature is particularly valuable where longer sizes are being processed. the squeegee print stroke. This feature enables more precise line definition and thickness control, ensuring more repeatable image The removable stack magazines give magazine-to-magazine location and geometry. operation and also protect substrates while being transported from The Torsion Bar Squeegee Head is claimed to be a unique design. one process to the next, or stored temporarily between processes with This assembly enables extremely precise squeegee pressure setting and different flow rates. By maintaining a stock of magazines close to the control as well as separately adjustable down stop and flood equipment it can be kept running continuously with the minimum of positioning. Squeegee angle of attack is also adjustable with readout. attention by the operator. Through simple switch setting the operator may use the machine in Magazine capacity for substrates 0·025 in. thick is 400 new, and normal print or flood mode, as well as alternate direction and double between 300 and 350 after printing, depending on the production stage print modes. reached. Handling rates depend on substrate size, being normally A major feature of thick film screen printers is the requirement for 1200/hour for 2 x 2 in. extremely precise registration accuracy. This will make the 24 in x 24 in A central control and safety system monitors magazine loading and area Model 2405 attractive to producers of precision fine line unloading and substrate feed throughout, audible warning being given multilayer PCBs, large area ceramic substrates, liquid crystal displays, if magazines need servicing or if an out-of-tolerance or faulty etc. substrate is detected. Warning lights show the operator where attention is required. BFI Electronics Ltd., 516 Walton Road, West Molesey, Surrey, KT8 0QF. DEK Printing Machines Ltd., 22 Albany Road, Granby Industrial Estate, Weymouth, Dorset DT4 9TH. Telephone: (030 57) 74431. Telex: 41122. Soldering Flux Fry's Flowsolder R8 soldering flux was introduced for automatic Silver Filled, Modified Polyimide for Chip Bonding soldering of printed circuit boards almost ten years ago. Users realised the advantages of this flux in producing perfectly soldered, assembled, Alpha Metals have introduced EPO-TEK P-1011, a single printed circuit boards and it quickly became the most widely used flux component, modified polyimide silver system designed for chip of its type in Europe. bonding in microelectronic and optoelectronic applications. Fry's now introduce the series 800 fluxes which, if used on a PC Specially designed for screen printing and dispensing, EPO-TEK board that has been coated with a silk-screened solder resist, will leave P-1011 solves many problems inherent in most polyimides. no "white deposit" after cleaning in a fluorocarbon solvent. This Possessing both high electrical and thermal conductivity, the means that, by choosing the right flux, the right solvent and coating material has a continuous operating temperature of 350°C, but can be the boards with a silk-screen solder resist, no white powder or residues exposed intermittently to temperatures as high as 500°C without will be left on the board after cleaning. degradation of bond strength or electrical conductivity. Even under The series 800 fluxes have all the properties of the Fry's R8 range, severe high temperature ageing, it maintains a high electrical accepted world-wide as the standard flux for automatic soldering. The conductivity of 0·000016 ohm-cm. reduced activity produces a halide level below 0·5% as specified in EPO-TEK P-1011 can be screen printed on the back of IС and LCD many military specifications. Residues can be cleaned from circuits to gold-backed silicon wafers and then B-staged. After application, MIL P28809 standard. wafers do not have to be immediately diced. Instead, they can be There are three standard grades at present available and Fry's stored for several months. In automatic pick and place of die, chips technical personnel can advise of the type best suited for your are bonded instantly on lead frames when a heat column particular operation. The series 800 fluxes can be used for foaming, (350°C-400°C) is employed. wave fluxing or dipping. Other complications usually associated with polyimides are also eliminated. EPO-TEK P-1011 will not attack the emulsion or squeegee Fry's Metals Limited, Tandem Works, Christchurch Road, London during screen printing. In addition, it frees the user from having to SW19 2PD. Telephone: 01-648 7020. frequently add solvent and clean clogged screens. With a low chloride content of 13 ppm, no need for refrigeration, and room temperature shelf-life in excess of six months, EPO-TEK P-1011 provides a valuable solution to screen printing and dispensing Polymer Thick Film Products applications. A completely new range of Polymer Thick Film Resistors and Alpha Metals Ltd., 457 Kingston Road, Ewell, Surrey, Telephone: Conductors are available from EMCA. The 4000 Series is a mutually 01-394 1641. Telex: 929818. blendable system covering the range 10 ohms per square to 10 gigohms (109) per square. TCR is ±200 ppm/°C over most of the range and the inks are compatible with a wide variety of substrate materials both rigid and flexible. Designed for curing at 165°C, it is also possible to Glazed Film Chip Resistor use up to 350°C in air or up to 700°C in nitrogen to provide shorter curing times and/or pretreatment for extremely harsh environments. Tekelec announce the introduction of a low cost, metal glazed film Standard 200 mesh stainless steel printing screens may be used, or if chip resistor. preferred, the 4000 Series is compatible with most monofilament, e.g., Manufactured in Japan and measuring only 3·20 mm x 1·60 polyester, materials. These new compositions offer outstanding mm x 0·60 mm thick the chip is available at either ±5% tolerance stability to environmental and electrical stress and are extremely between 10 ohm and 3·3 M ohm and ±2% tolerance between 100 ohm solvent resistant. and 470 К ohm. 2540 and 2541 are new solderable polymer silvers compatible with Rated at 0·125 watt and 200 volt (max) working, the chip is ideal the 4000 Series. 2540 was developed to be compatible with for ultra thin packages. conventional PCB laminates and 2541 for the newer high temperature Typical price is £2.00 per 100 pieces in quantities of 1000. substrates. 2541 offers remarkable conductivity at 0·005 ohms/sq/mil. Tekelec Components Ltd., Philpot House, Station Road, Rayleigh, EMCA, London Road, Sawston, Cambs. CB2 4EF. Telephone: Essex SS6 7НИ. Telephone: (0268) 778433. (0223) 834612
Microelectronics International – Emerald Publishing
Published: Jan 1, 1982
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