Issue link: https://iconnect007.uberflip.com/i/1002143
16 PCB007 MAGAZINE I JULY 2018 it is absolutely necessary. There was no way around it. Solder mask is going the same way in order to achieve good yields and meet the technology demands. Matties: Are there any equipment suppliers coming to you looking for a recipe for inkjet printing? Tibbals: Yes, this has been a large part of our R&D focus. We see the next stage for sol- der mask development as be- ing the inkjet process. Inkjet technology is still under de- velopment, currently there is no fully commercialized inkjet solution on the market for vol- ume production but there are several installations you can probably class as beta sites, so we are almost on the cusp. Matties: Speed is a big issue. Tibbals: Yes, it is. First, we should take a step back and appreciate just how much of a chal- lenge inkjet solder mask is. You're starting from scratch. It's completely different from a photo- imageable formulation. For a start the viscosi- ty is close to 1000 times lower; it's 100% solid; it must have the required jetting characteristics and the particle size is now measured in nano- meters not microns. The challenge is to be able to deliver a solder mask material which has all the required features and still meets or exceeds the essential requirements of end performance and end resistance. This is not a straightfor- ward exercise. This is a project we've already been working on for several years, and I'm happy to report good success. And there are now several equipment manu- facturers who are in the latter stages of devel- opment and bringing machines to market. As we all know, there have been false dawns for inkjet application of solder mask but machine manufacturers have come on tremendously in terms of the equipment development. Some of that has been enabled by the ability to process data faster and some from inkjet head tech- nology improvements in the resolution and frequency they can deliver. When you look at how the technology has moved on, it's now at the stage where it is becoming a viable solution. If you look at inkjet solder mask and relate it back to the problems and challenges we first talked about—miniaturization, smaller fea- ture sizes, registration, etc.— we can see that it has all the features to offer an excellent solution. Inkjet is a digital process; by its very nature it will give us the registration that we require and won't put any ink in the holes. So, with one process, we start to address the two fundamen - tal limitations of traditional photoimageable solder mask. We then throw in all the oth- er benefits: 100% solids, we have no VOC emissions so it's a cleaner process; eliminating three major stages of the current solder mask process and all the energy that's consumed and the waste - water produced, plus the reduction in capital equipment, maintenance and footprint; the list goes on. For us, inkjet is very much the future for sol- der mask. It's not necessarily going to be the universal solution next year, but it is coming and will gradually percolate its way through the solder mask production areas. I think it will start off probably with the smaller volume pro- duction and will gradually grow in the same way that many years ago photoimageable sol- der mask took a while to grow, and dry film resist took a while to grow. But, there are so many benefits associated to it that I think there will be a big pull to bring it through. Matties: In terms of the solder mask process, curing is a large consumer of time. Will ink- jet reduce the curing time? And by not using inkjet, the more traditional route, are you do- ing anything to have something that could be cured say, in half the time? Or, even less? Antony Earl