Due to the recent increase in interest regarding Epoxy Flux, there are a number of general questions that many people have had about the this unique enabling technology. I decided to sit down with the brains behind the Epoxy Flux materials here at Indium Corporation, Dr. Ming Hu and Lee Kresge, to get their take on some of the most commonly asked questions.
Chris: Why would someone want to use Epoxy Flux in their manufacturing process?
Ming: The most common reasons someone would use Epoxy Flux in their manufacturing process is that they are looking to reduce cost and increase reliability. Epoxy Flux can provide higher drop testing reliability than a solder joint without a polymer addition. Many people are looking to eliminate their underfill process because of the cost of this material and the additional processing steps involved. The additional processes take extra manufacturing time, and the extra equipment needed requires further expenses, including the initial cost of equipment, operational costs, and maintenance. Epoxy Flux can eliminate the extra manufacturing costs by eliminating the extra processes. There is no need for extra equipment because the pick-and-place equipment typically has dipping units built in for PoP assembly. Dispensing or Jetting equipment can also be used. The epoxy flux is applied before the board is reflowed and cures during the reflow process. Although Epoxy Flux will provide higher drop test reliability than a conventional epoxy flux, the reliability is not as great as an Underfill. Therefore, if you use the Epoxy Flux materials, you will want to determine if the drop test reliability is great enough for your application and product.
Lee: Epoxy Flux can also be used to mitigate dendritic growth concerns under low standoff components such as TMV PoP packages. Conventional PoP Flux may have trouble outgassing properly if the standoff or gap between the component is too small and this could cause an electrical reliability concern. Epoxy Flux has a hard post reflow residue that can protect against dendritic growth between the component bumps and cause shorts. The hard post reflow residue can also aid in compatibility with other post reflow processes like underfilling where no-clean flux residues may be soft and incompatible with these other polymer materials.
Chris: What types of components can Epoxy Flux be used with, and who is interested in this material?
Ming: Typically, Epoxy Flux is used in similar applications that underfills are used in. These include, but are not limited to, BGA, CSP, and other bumped component assemblies because these are the most susceptible to drop shock failures. People are also interested in improving their thermal cycling performance of these bumped components. Epoxy Flux, in most cases, isn't the answer at this time. However, we have had customer feedback showing an improvement in this region with our materials compared to solder joints alone and underfill.
Lee: SMT applications are the most prevalent applications that people are testing Epoxy Flux with currently. However, we have also seen a recent drive and an increase in interest from the semiconductor market as well.
Thank you Ming and Lee for taking the time to answer some of these popular questions.
Stay tuned for my next post... Epoxy Flux: Storage and Handling
* This post is part of the Understanding Epoxy Flux: The Need and the Process series.