The Powder Size chart (Figure 2) cross-references particle size to typical printing and dispensing requirements. Having selected the best alloy, particle size is next. If a solder joint needs to retain physical integrity during a later operation, such as a second reflow process, the peak temperature of the later operation needs to be below the solidus temperature of the alloy. While wetting begins at the solidus temperature, best wetting is achieved at a peak temperature 15º C or more above the liquidus. Alloys are called eutectic when the solidus and liquidus are equal. In between the solidus and liquidus, a region called the plastic range, some portion of the alloy is solid but the majority is liquid.Below the solidus, an alloy is 100% in a solid state.The phase change from the solid state to the liquid state begins upon reaching the solidus and ends upon reaching the liquidus. *Eutectic – Solidus and Liquidus are equal **MP – Melting pointĮach alloy has temperatures at which it changes from solid to liquid ( Figure 1). Some applications that fall under the RoHS directive are exempt from being lead-free because the reflow temperature requirements can only be met with high-lead solder alloys which are exempt under RoHS regulation.įigure 1. Sometimes this is due to the product falling under the RoHS (Restriction of Hazardous Substances) directive and sometimes it is a corporate directive. Many applications have a requirement for use of lead-free solder alloy. What type/size does the power need to be for the smallest feature in the application?. Is there a reflow temperature requirement or limitation?.When choosing a solder alloy, there are a few questions that need to be answered. It is always worth a call to your Nordson EFD solder sales specialist to review requirements to ensure you are using the best solder paste for the job. There are additional details of alloy and flux performance not covered that can be very important in the selection process. This guide covers the most significant steps in selecting a solder paste.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |