Issue link: https://iconnect007.uberflip.com/i/1091269
MARCH 2019 I PCB007 MAGAZINE 91 I signed off the machine with two guys from Holland from a great company who were very skilled engineers. The work progressed and was regularly punctuated with breaks for meals. It is impossible to talk about trips to Asia with - out mentioning the food. We sat down to lunch one time to a perfectly presented meal of sushi presented in a stacked box. When you laid the meal out in front of you, there were perhaps 20 beautiful individual pieces. Even though nei - ther the Dutch guys or I could use the provided chopsticks very well, we tucked in as best we could. Amongst the pieces was a small green item that looked like a perfectly formed invert - ed thimble. One of the guys with me picked it up and put it in his mouth before our host could stop him. He instantly went white, and I could see his eyes scanning the table for all cold liq - uids he could put in his mouth; a mouth full of Wasabi will do that to you. He survived without lasting damage, although I expect he remem- bers the experience even more vividly than me. Just before it was time to leave to return to the U.K., we were lucky to experience the Cherry Blossom festival. Linda and I walked around the local park along with literally thou- sands of local people. At one point, we were separated by a few meters due to the density of people meant I just had to go with it. It was easy enough to see Linda anyway due to being quite tall compared to the local population, and her blonde hair was unique as far as the eye could see. I remember small children reaching out to touch her hair to see if it was real. The main event for this trip was the test ma- chine, and it was a great piece of kit. It was manufactured to be able to test a 1.2 m back panel up to 12 mm thick. It had very enhanced test capability compared to other machines of this generation, and the high-accuracy resis- tance test with resolution to a single milliohm worked extremely well so much so that it was successfully used to detect plating defects in individual holes. The test method for this was simple enough; each hole barrel had to be indi- vidually resistance tested, and the results were recorded and mapped. The normal resistance of a perfect hole was proven to be consistent across the whole panel for each hole size. The resistances in question were small—just a few milliohms—but if there was a defect in the plating, the resistance might be a couple of milliohms higher than all of the good holes. When you consider that you may be search- ing for a defect rate less than one in two million holes, then you understand that there was a lot of testing to find only a few faults. In this case, the value of the circuit boards justified the ef- fort involved, and every panel had to undergo this enhanced test. When a failure occurred, the hole in question was microsectioned and the nature of the defect identified. If these de- fects had made it into the final assembled prod- uct and installed in the field, there would have been a high risk of premature failure. In this case, the potential cost of failure in the field drove the whole project, justified the price of the tester, and the added manufacturing time required for the special test. Japan has some happy memories for me, and it is a country I would recommend to any- body travelling for pleasure. The super polite and friendly nature of the Japanese people al- most guarantees you a great experience. Bow- ing at every opportunity is quite infectious, and I could not help myself from continuing for weeks after I returned home. PCB007 Marc Ladle is a director at Viking Test Ltd. To read past columns or contact Ladle, click here. When you consider that you may be searching for a defect rate less than one in two million holes, then you understand that there was a lot of testing to find only a few faults.