SMT007 Magazine

SMT-July2016

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90 SMT Magazine • July 2016 by Ahne Oosterhof EASTWOOD CONSULTING Using modern laser systems for the de- panelization of circuit boards can create some challenges for the production engineer when it is compared to traditional mechanical singu- lation methods. Understanding the effects of the laser energy to the substrate material prop- erly is essential in order to take advantage of the technology without creating unintended side effects. This paper presents an in-depth analysis of the various laser system operating parameters that were performed to determine the resulting substrate material temperature changes. A theoretical model was developed and compared to actual measurements. The investigation includes how the temperature increase resulting from laser energy during de - paneling affects the properties of the PCB sub- strate, which varies from no measurable change to a lowering of the surface resistance of the cut wall depending on the cutting parameters. In addition, the amount and properties of the ejecta that are potentially resulting from the laser processing is investigated. Understanding the composition and quantity of any resulting residue may have a great impact to both the board design and the selection of the appro - priate circuit board singulation method that will achieve the best possible results. An en- ergy dispersive X-ray analysis method (EDX) was performed to investigate if any unwanted material compounds are present on the cutting sidewalls of an FR4 circuit board substrate as a result of laser energy induced during the de- paneling process. Depaneling Methods Many depaneling methods are being used in the industry, such as: 1. punching/die cutting 2. v-scoring 3. wheel cutting/pizza cutter 4. sawing 5. water jet 6. routing (+nibbling) Some of these are useful only in very low cost, minimal quality applications; others can only be used for rectangular boards. Several can ARTICLE

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