How do we measure the O2 ppm in N2 environment. I don't understand why the customer keep insisting me to use N2 instead of Air. I don't see the need for it as I done have any soldering issue. Can you share with me why N2 is needed at the first place. Apart from ppreventing Oxidation, what good can it brings. I knew it gives me more problem to Tomb Stone due to the higher surface tension. Pls help me on how to convince my customer not to take this a big issue.
Hello Yngwie, When we look at the technical benefits of using N2, you'll find that your customer is trying to get a better product. Now as we discuss just a few of the reasons to use N2, when O2 is present in the heating atmosphere it carries oxides that will cause oxidation as you already know, but what's important about this point is that minimizing the oxide contaminants in the atmosphere improves better wetting characteristics during reflow. Better wetting improves solder flow and increases the integrity of the mechanical and electrical connection. One attributal benefit is less tombstoning. Another is better self-alignment of components as a result of less surface tensions. If you can convince your customer that your process is in control and that product quality is not affected with your process setup then I'm sure they will listen, but based on my experiences with N2, your customer has some valid concerns. What is your reluctance to using N2? You may want to investigate doing some tests and compare same product with and without N2. You certainly should work with your customer to establish common ground and create a solution that fits both of your requirements. Let me know if you require additional assistance. Thanks!
Another value add of N2 is when you are running a gold over nickel process it is recommended that you reach a peak of 220c instead of 215 when running in air. When you add N2 you can maintain that 215 number with the same results. If you look at your IC specs you will find that most of them are 220c max. Your customer may have some concerns about stress too. As a side note there is a company I just discovered in Charlotte NC that makes a machine you pump compressed air in and you get 99% nitrogen out! I haven't seen all the numbers yet but from what I think I know this could pay for itself in 9 months! http://www.domnickhunter.com
Hello Doug, thank you for the additional commentary, it has reminded me of another reflow recommendation that I'd like to make in general for readers. It's not specific to O2/N2 in ovens but in the method for creating and managing profiles for numerous products. Creating specific profiles for a smaller number of products is usually the way to go but when you have 250 different products that mostly are double sided design, your individual number of profiles becomes outrageously large to manage. What we did with our ovens was maintain an optimzed reflow profile with correct temperatures in each zone. Then we categorized each type of temperature profile (extra low, low, medium, high, extra high) based on speed alone. Temperatures remained consistent, all that changed was conveyor speed which made a huge impact in product changeover cycle time. It's quicker to adjust conveyor speed at maybe 30 seconds rather than wait for an oven to stabilize after loading a new lower temperature profile which could take 30 minutes or longer in some cases. Just some recommendations for those who may be having difficulties managing a high number of oven profiles. It worked very well for us. Let me know if you require additional assistance. Thanks!