Issue link: https://iconnect007.uberflip.com/i/1207026
80 SMT007 MAGAZINE I FEBRUARY 2020 to get the solder volume that you want, as well as the consistency in solder deposits. Matties: Do they rely on their suppliers like Indium Corporation to develop products that will suit this application? Nash: Yes. From a solder paste or a material standpoint, we're challenged with these minia- turization topics, including finer pitch, tighter spacing, etc. Some of the stuff that we work on is finer powders. The industry, especially the mobile industry, is looking at Type 5 powder and Type 6 powder. I haven't seen any main- stream mainboard technology going into Type 7 at this point, but we do see system-in-pack- age (SiP) applications where Type 6 and Type 7 are mainstream solder paste technologies. However, the flux vehicle for the solder paste has to keep up with the finer powders, too. You have a number of things that come into play there, including that higher surface area of the powder creates more oxide/oxygen con- tent, so the flux has a tougher job cleaning the oxides. Essentially, there's more oxide, so it's going to stress the flux a little bit more than normal. But you have less flux present because you have less solder paste volume present with smaller apertures. From the powder-size standpoint, we don't have an issue. It's well-known that we can go finer in powder size and powder distribu- tion to Type 6, Type 7, and we've done Type 8 before, but when you get to the Types 7 and 8, you're talking more about SiP applica- tions rather than a mainstream circuit board assembly. Some of the other challenges that you might face with solder paste and the finer powders might be graping where the sol- der deposit doesn't coalesce completely. You might have greater head-in-pillow challenges because there's not as much solder paste pres- ent. A lot of the other challenges would be more focused on the reflow process rather than printing process. Matties: When a customer comes to you, are they looking at this as a total process? Are they getting recommendations for stencil material, jet, or paste? Nash: They are. A lot of people are looking at this as cutting-edge technology. Most of the people that are coming to us have never dabbled in it or have dabbled in it a little bit, and they're asking for our recommendations on processes and materials. The two go hand in hand with each other because even if you have the greatest solder paste in the world, you aren't going to be able to fully utilize the material unless your process is also optimized. Thus, it's extremely important to look at the process, and Indium Corporation has done that for quite some time now. We feel that to be successful, you have to focus on both the material and process and optimize both for the assemblies that are being built. Matties: When you say processes, how do you define those? Where do you set the boundar- ies—as soon as the data comes in from the fac- tory, or in the imaging area? Nash: We look at the entire process, which starts at the material supply, ensuring that the customer is getting the material in the best condition as possible. There are a number of processes within manufacturing as well, such as the printing process, which will determine the volumetric transfer efficiency of the solder paste. The SPI equipment will help to deter- mine the consistency of the transfer efficiency and make sure that you don't have any defects with regard to bridging, insufficients, or exces- sive solder deposits. From a solder paste or a material standpoint, we're challenged with these miniatur- ization topics, including finer pitch, tighter spacing, etc.