Sze Pei Lim: Currently, for the ball-attach process, customers are facing issues like warpage of the substrates. Sometimes you may not be able to deposit enough flux on the substrate, or the balls may just roll away because it's not flat. Then you will have problem like missing balls, or some of the balls may join with the neighboring balls and become a bigger ball – a double ball – that we see in the industry. These are some of the typical problems that you may see for the ball-attach process.
Our new Indium WS-575-C-RT ball-attach flux is one of our key foci right now. This is a product that really gives us a very good tackiness, even during reflow, so it can hold the balls very well. It can be used as a one-step OSP process, so it can shorten the process time and the cost of running through a second reflow.
The first pin transfer that you do after 8 hours, it is still very consistent. The volume that is deposited onto the substrate is very consistent over a long period of time. It can be stored in room temperature for 6 months without any issue.
Some of the other advantages of Indium WS-575-C-RT is the rheology of the flux and also the stability across the long hours of working life. It doesn't create any exposed pad on the substrate, so it is a very good product we use for the ball-attach flux.