PCB + ASSEMBLY The process flow for shield assembly with solder preforms. Source: Indium the solder paste is printed, a chip shooter places the tiny passives and small components. An component placer puts the ICs in place and later the shields. The solder preforms are then arranged by the IC placer. After these steps, the PCBA goes into the reflow oven. It is possible, but not likely, that the placement of the preforms could slow the IC placer down. These types of applications have been implemented with high yields and reliability. In conclusion, solder preforms enable a low cost, reliable solution to solder starvation in Faraday shield assembly for mobile phones. In addition, the process is part of the in-line electronics board assembly and the final result is not visible to the end user. Capacitor terminal applications Terminals of large capacitors can also experience solder starvation. In one such application, 0603 size preforms were placed near the capacitor terminals. In this application, the number of solder-starved related defects was reduced by 95 % after using preforms. Conclusion Solder preforms can be an economical way to solve solder starved conditions in various types of SMT (surface mount technology) assembly applications. It is always best to consult with the technical support team at your solder supplier to be sure that the correct solder, solder form, and flux best suit your application. SMT Hybrid Packaging, Booth 4-321 www.indium.com References 1) Lasky, R. C.; Jensen, T.; Practical Tips in Implementing the “Pin in Paste” Process, at SMTAI, Chicago, IL, Sept. 2002. 2) Berntson, R. B.; Lasky, R. C.; Pfluke, K. P.; Through-Hole Assembly Options for Mixed Technology Boards, SMT Magazine, Aug. 2004. Portions of this information were presented at SMTAI 2010 in Orlando, FL, and APEX 2011. Zusammenfassung Bedrahtete Bauteile, meist Passive, werden oft im Wellen oder Selektivlötverfahren mit dem Board verbunden. Sind jedoch auf Baugruppen sowohl oberflächenmontierbare als auch bedrahtete Komponenten gleichzeitig eingesetzt und wird per Reflow zusammen gelötet und die bedrahteten Teile vorzugsweise oft im Pin-in-Paste- Prozess verarbeitet. Allerdings gibt es dabei immer wieder Applikationen, in denen dafür das vorher auf die Leiterplatte aufgedruckte Lotdepot nicht ausreicht. Mit Lot-Preforms wie Solder Fortification, also dem Einsatz vorbereiteter Lotelemente, bietet sich hier eine ausgezeichnete Lösung. Es gibt Applikationen, in denen die Lötdefekte um maximal 95 % reduziert werden konnten. Résumé Les composants câblés, généralement passifs, sont souvent assemblés à la carte par soudage à la vague ou par soudage sélectif. Des composants câblés en surface et des composants câblés et soudés par refusion et les parties câblées sont de préférence soudées à l’aide de la technologie pin-in-paste. Cependant il existe toujours des applications dans lesquelles un dépôt de soudure sur le circuit imprimé ne suffit pas. Les préformes telles que Solder Fortification, donc l‘utilisation d’éléments de soudage préfabriqués, apportent une solution excellente. Il existe des applications dans lesquelles les défauts de soudage peuvent être réduits de 95 % maximum. Резюме Компоненты с проводкой, чаще всего пассивные, часто соединяются с платой при помощи пайки волной припоя или селективной пайки. Если же в узлах одновременно как компоненты с поверхностным монтажом, так и с проводкой, которые спаиваются при помощи пайки оплавлением припоя, то компоненты с проводкой предпочитают часто обрабатывать по технологии PIP. Тем не менее, всё же существуют варианты применения, при которых ранее нанесенного на печатную плату запаса припоя недостаточно. В этом случае потребителям предлагается превосходное решение благодаря мерам подготовки к пайке, таким как укрепление пайкой, то есть использованию подготовленных элементов для пайки. Существуют определённые задачи, в которых можно уменьшить количество дефектов пайки как максимум на 95 %. 78 EPPEUROPE May 2017
PCB + ASSEMBLY PRODUCT UPDATES 100% process control for selective soldering system SEHO Systems GmbH, a manufacturer of complete solutions for soldering processes and automated production lines, will focus on automatic process control at the upcoming SMT Hybrid Packaging show, scheduled to take place May 16–18, 2017 at the Messe in Nuremberg, Germany. The selective soldering system SelectLine-C has been even further optimized. The company will introduce its new cross sensor at the exhibition that takes over several functions. On the one hand, the wave height is precisely controlled. The measurement is made touchless directly at the solder nozzle and it is fully independent from the solder alloy used. In addition, the cross sensor is also used for automatic tool measurement: diameter, height and mounting position of the solder nozzle are automatically controlled, thus excluding potential operator errors. Also new, being introduced for the first time is an automatic nitrogen flow quantity control. The company offers the opportunity to integrate additional processes directly into its selective soldering systems. This includes, for example, a brush system for solder joint cleaning or an AOI system for automatic detection of soldering defects. The benefits are obvious: no additional floor space is required in the production area. At the same time, production costs will be reduced as the entire board handling is performed by the axes systems that are integrated in the selective soldering machine anyway. By adding an intelligent handling concept, assemblies that have been identified as defective can automatically be removed from the Tool measurement will be shown at SMT. production line. The new process control functions ideally supplement already existing features such as flux quantity monitoring, monitoring of the nitrogen quality or the automatic position and z-height correction thus ensuring a 100 % process control. SMT Hybrid Packaging, Booth 4-129 www.seho.de Source: SEHO Systems GmbH Tin-lead, water-washable solder paste Henkel’s development continues with the commercial launch of Loctite HF 2W, a tinlead, water-washable solder paste designed for high-throughput, high-yield production. Halide- and halogen-free and REACH compliant, the solder paste addresses environmental responsibility while delivering outstanding performance for Pb-based soldering. The solder paste is available with a standard, tin-lead Sn63 eutectic alloy, as well as the company’s proprietary anti-tombstoning 63S4 alloy. The material’s properties allow it to reflow at high temperatures, expanding the reflow process window to facilitate strong intermetallic formation between the tin-lead paste and lead-free and tin-lead components. The result is excellent solderability in air or nitrogen across a broad range of challenging surface finishes including OSP- Cu, ENIG and silver. The material is suitable for high-speed, fine-pitch printing, with a wide print window and excellent results on components as small as 0201s, keeping defects such as solder bridging to a minimum. In addition, Loctite HF 2W flux residues can be cleaned via ultrasonic and spray under immersion cleaning processes as many as seven days post-assembly, providing assembly specialists with maximum flexibility. The solder paste has been formulated for high-reliability applications such as those found in the medical, hard disk drive, aerospace and defense markets, among others. SMT Hybrid Packaging, Booth 4-241 www.henkel-adhesives.com/electronics Powerful and Compact The LPKF MicroLine 2000 Ci sets new standards in laser cutting of rigid, flexible and flex-rigid circuit boards. Discover the new benefits of using lasers. Find out more: www.lpkf.com/laser-depaneling SMT: 16 – 18 May 2017, Hall 5, Booth 434A EPPEUROPE May 2017 79
