Tin/lead solders do NOT melt at 183C, they solidify at this temperature, called the solidus temperature. For eutectic tin/lead solder, consisting of 61.9%Sn/38.1%Pb, the liquidus temperature is also 183C, for all others the liquidus temperature is higher depending how far from eutectic the mixture is. Other constituents, e.g. copper, also will raise the temperature above which solder is liquid. But it is not temperature, that makes a solder joint, but heat. It takes a certain amount of thermal energy for the solder to flow, go into solution with the base metal (e.g., copper, nickel-requires even more heat, Alloy 42-requires even more heat, Kovar-requires even more heat). The thermal energy available depends on the temperature, the heat transfer conditions, the time at temperature, for the most part. That is why one gets good solder joints at lower temperatures for vapor phase reflow than for forced convection reflow, and lower temperatures for forced convection reflow than infra red reflow. A good rule of thumb for forced convection reflow soldering to copper surfaces is liquidus+20C (so your 213C may not be high enough for larger components depending on the solder composition you use) and liquidus+35C for soldering to Alloy 42. These higher than liquidus temperature assure good wetted solder joints even for larger components, that heat slower because of the larger thermal mass, without overheating and damaging the components. If you are interested, I give a workshop "Practical Design and Prediction Methods for Surface Mount Solder Joint Reliability" at NEPCON West'97 that would help you. Course Content: The objectives of this course are to make the participants familiar with the underlying technical issues; provide insights in the relative importance of product quality resulting from workmanship standards and process controls, and focused 'Design for Reliability;' give them an appreciation of the reliability pitfalls in the design, testing, as well as environmental stress screening (ESS) of electronic assemblies; and to present state-of-the-art, but simple to apply, tools for the 'Design for Reliability.' The attendees of the course will have an understanding of the solder behavior under load and fatigue which is necessary for the successful design, manufacture, and testing of electronic assemblies. Processing issues to achieve the consistent solder joint quality necessary to assure reliability will also be discussed. The information presented has been included in the industry documents IPC-SM-785, 'Guidelines for Accelerated Reliability Testing of Surface Mount Solder Attachments', IPC-D-279, 'Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies', ANSI/IPC J-STD-012, 'Implementation of Flip Chip and Chip Scale Technology', and ANSI/IPC J-STD-013, 'Implementation of Ball Grid Array and Other High Density Technology'. Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 USA Phone & Fax: 201-543-2747 E-mail: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************