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JUNE 2020 I PCB007 MAGAZINE 99 their UV ink supplier is happy with the proposed change of equipment. When you do this for the first time, nobody is able to say with any level of certain- ty that it will work. I did talk directly to the ink supplier, and they were ex- tremely helpful but also quite skeptical that it would be pos- sible to get a positive result. It seems that poor past experi- ence of LED-based curing had galvanised opinions against this format of machine. There is no substitute for test- ing on real products, and in this respect, Merlin Circuits in North Wales has been a huge help. They have run the machine alongside their old vapour lamp ma- chine and made a true side by side comparison with testing and verification of the results be- ing made by their UV ink supplier. The target for the company I work for is to sell these ma- chines, but the results we have seen from the testing work at Merlin Circuits (Table 1) have raised some points which may have some wid- er technical interest. The results for the LED machine were all good when running at 1 m per minute and 2 m per minute, but one of the adhesion test re- sults was poor when running at 3 m per min- ute. This is not surprising, as the processing speed was quite extreme for a machine format- ted with only two LED light bars (Figure 1). The modular design approach means that an appropriate number of bars could be fitted if higher speeds are important to the user. One interesting result from the trial was the difference between vapour bulb and LED ma- chine with regard to printing component ident onto the panels. The panels were UV bumped on both types of machines and then printed with component ident. There was a notable difference in ident adhesion between the two processes. The ident did not adhere well on the panels processed with the vapour lamp machine (Figure 2), but the adhesion was very good on panels processed with the LED ma- chine (Figure 3). Figure 1: A two-light-bar machine format. Figure 2: Vapour bulb processed panel with poor ident adhesion. Figure 3: LED processed panel with good ident adhesion.

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