PCB + ASSEMBLY high cutting gas pressure, an average power that is too low, and a large material thickness cause surface spatters. These material deformations can lead to defocusing and disruption of the punch process. The maximum material thickness is thus restricted insofar as the heat distortion depends on the material thickness and increases with increasing melt volume. To avoid overlapping of heat-affected zones for adjacent holes, the maximum adjustable speed should be oriented to the cooling time and the size of the hole pattern. Additionally, hole size, material thickness, cutting gas pressure, and cutting gas type affect the expulsion height. The hole size and the material thickness have an effect on the melt volume, which is proportional to expulsion and dross. Similarly to step-up welding, expulsion is lower for a cutting gas with a low oxygen content than for a cutting gas with a high oxygen content. However, expulsion, in contrast to dross, decreases with increasing oxygen content. Smaller holes can be generated with oxygen at lower material gauges. The opening ratio, or the ratio of generated holes to stillclosed holes, is also higher. With decreasing oxygen content, the heat-affected zone size decreases and the maximum material thickness to be processed also decreases. Percussion drilling in metal foils In percussion drilling (also known as „piercing“), in order to make each aperture or cutting line, a hole is first produced in the material by pulses. Then the actual cutting process begins. Spatters are thereby produced on the material surface. They should not be too large and should be as low in number as possible because they can deposit on the inside walls of the nozzles and plug them. Deposits hamper discharge of the melt, enabling burrs to be formed on the exit side of the beam. A larger hole diameter prevents nozzle clogging but also increases the amount of molten material that must be removed from the hole. Production of ultra-fine cutting elements with the StencilLaser For cutting elements, cutouts in the individual parts as well as the outer contour must be considered. Cutting and fast cutting techniques allow for precise outer contours. If tabs are required for keeping parts in focus, they must be able to be separated easily A thorough study of the process parameters is given in the LPKF tech paper „Quality Considerations in Stencil Applications.“ Zusammenfassung Der stetig steigende Qualitätsanspruch macht auch vor Lotpastenschablonen und Schneidteilen nicht halt. Ein Applikationsteam des Laserspezialisten LPKF hat sich eingehend mit Qualitätsmerkmalen befasst. Anhand umfangreicher Testläufe haben die Experten einzelne Qualitätsaspekte genau unter die Lupe genommen. Zugleich haben sie die Ergebnisse in einem TechPaper zusammengefasst, um allgemeingültige Qualitätskriterien in verschiedenen Anwendungsbereichen zu optimieren. Résumé Une exigence de qualité toujours plus grande ne s‘arrête pas aux pochoirs pour pâte à braser et les pièces découpées. Une équipe application du spécialiste du laser LPKF s‘est concentrée sur les critères de qualités. Lors de tests poussés, les experts ont scruté à la loupe certains aspects de qualité. Ils ont collecté les résultats dans un TechPaper pour optimiser les critères de qualité généralisables dans divers domaines d‘application. Резюме Постоянно растущие требования к качеству заставляют модернизировать в том числе и шаблоны для паяльной пасты и режущие части. Группа по вопросам применения специалистов по лазерному оборудованию LPKF вплотную занялась характеристиками качества. На основе множества тестовых пусков эксперты подробно рассмотрели отдельные аспекты качества. Результаты были сведены в техническом документе для оптимизации общих действующих критериев качества в различных областях применения. from the surrounding material. The tab width varies according to material type, material thickness, and magnitude of sheet stress. For a higher material thickness, the tabs can be narrower, whereas for a higher sheet stress, the tab width must be increased. The tabs should be positioned to ensure minimal subsequent disturbance. At the same time, the contour quality can be improved through manual modification of the tab shape. Experience helps The company published a study of quality aspects for different applications in a tech paper, which is available in English and German for free download from the Knowledge Center on the company Web site. SMT Hybrid Packaging, Booth 5-434 www.lpkf.com Source: LPKF 62 EPPEUROPE May 2017
PCB + ASSEMBLY Low cost SMT rework system PACE Worldwide announced the ST 925 convective and infrared system for SMT rework which combines three popular products together into one convenient, low-cost system. It is comprised of the ST 325 programmable convective/hot air rework station, the PH 100 low profile infrared preheater, and the ST 500A Z-axis platform. The system provides a 575 Watt convective topside heater plus a 1600 Watt IR bottom-side preheater which allows operators to safely rework PCBs for fast, efficient soldering, rework or repair, even on the highest mass, thermally challenging, lead-free PCBs. The system features a self-contained convective/hot air SMT rework station that is fully programmable and can be used to remove and install surface mount components. From the front panel, the system can be used in either manual or “timed” modes. Manual mode means that the system generates heated airflow when the cycle button is pressed. “Timed” PRODUCT UPDATES modes allow the operator to create up to 20 “Profiles” that consist of time and temperature parameters to ensure process control and repeatability. The system uses a pump to generate airflow that first passes through a heater, where it is warmed to the appropriate temperature, and then through optionally available heat-focusing nozzles that “shape” the air stream for the specific component. A userfriendly front panel interface with digital display allows for easy adjustment. SMT Hybrid Packaging, Booth 4A-120 www.paceworldwide.com T 925 convective and infrared system for SMT rework. Vapor phase soldering with advanced batch systems IBL Technologies, LLC today announced plans to showcase its BLC 420 batch soldering machine during SMT Hybrid Packaging show in Nuremberg. The BLC reflow vapor phase soldering system is perfect for medium to high volume production, batch and inline machines. The machines offer the highest quality performance with the smallest footprint. Many patented features are available and provide a Source: PACE Worldwide wide range of flexibility, including: • Small footprint • Low power consumption • Real time temperature profiling • Intelligent Profiling System • Excellent solder quality • Fast setup • One profile for most operations The company offers a full line of single vapor batch and inline type reflow systems. SMT Hybrid Packaging, Booth 4-205 THE PERFECT SOLUTION FOR YOUR WORK BENCH Full process and cost control included as standard Weller Generation WT Setting new standards in user-friendliness Best-in-class – attractive price / performance ratio Maximum flexibility – backward compatibility with existing soldering tools Weller Zero Smog TL fume extraction system WT hub connector facility for efficient integrated performance Prolonged clean air attributable to the exceptionally large filter capacity Automatic filter change notification system and audio-visual filter alarm Low sound level www.ibl-tech.com Source: IBL www.weller-tools.com BLC 420 batch soldering machine. More information EPPEUROPE May 2017 63
