Design007 Magazine

PCBD-Nov2016

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50 The PCB Design Magazine • November 2016 Last month, I looked at some of the criti- cal things you need to consider before select- ing your resin, which covered hardness, colour, viscosity and cure time. I do hope readers found this simple back-to-basics guide a useful start- ing point for further study and consultation. Of course, when it comes to the choice and appli- cation of resins, there's a lot of information to take in, and over the following months I hope to distil this and provide some useful tips and design advice that will help you in your quest for reliable circuit protection. Right, you've now chosen your two-part resin and it's time to mix the components and get to work, so this month I'm going to turn my attention to the all-important job of mix- ing the resin (Part A, to use the terminology) and hardener (Part B), taking care that you get the ratio right and that you are conducting this critical part of the procedure under the right at- mospheric conditions, and with all due regard for safety procedures. Get the mix wrong at this early stage and you will not achieve a satisfac- tory cure, which will ultimately lead to all sorts of problems later for the product you are pot- ting or encapsulating. Anyway, continuing the five-point guide format that I introduced last month, here are five things to make yourself aware of before you start mixing. Mix Ratio Quite possibly the most critical aspect of res- in mixing, which will have long term adverse repercussions if you get it wrong! There are two methods of mixing a resin with its associated hardener: by hand or using specialist dispens- ing equipment. If mixing by hand, then the ra- tio of the weight of the two components is the more useful method to employ. If mixing using dispensing equipment, then the volume ratio is used. If the job is relatively small, then you are likely to use a resin pack, which provides the resin and hardener in precise quantities, in sep- by Alistair Little ELECTROLUBE Resins: Five Essentials to Achieve the Right Cure SENSIBLE DESIGN

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