![]() In addition, different heating and cooling rates will have various effects on a variety of defects, adding more complexity to the balancing act. This is the biggest challenge for developing a profile, so developing a thermal profile for a PWBA with very large thermal mass components (e.g., a large ball grid array (BGA)) and small thermal mass components (e.g., 0201 or smaller chip resistors and capacitors) is a balancing act. All components, even though their thermal masses are different, must meet the same minimum and maximum temperature requirements. Establishing minimum temperature, maximum temperature and duration in a zone ensures formation of intermetallic bonding between the component leads and their corresponding footprint or land patterns on those pads. Thermal input is determined by temperature/gas flow settings in each zone, the number of zones and the belt speed, which stays the same in each zone. This is the key reason for developing a unique profile for each product. Even though different products, based on their thermal mass, require different amounts of thermal input, all products must achieve the minimum temperature (temperature above liquidus) without exceeding the maximum temperature (without damage to any components) within a defined time period (thermal profile). ![]() Because of this, appropriate temperature profiling is essential for ensuring high-quality solder joints. High cooling rates can also damage components and result in temperature gradients of sufficient magnitude to warp PWBAs and larger components and also fracture solder joints. Reflow soldering requires controlled rates of heating and subsequent cooling however, too rapid a heating rate can damage PWBAs and components. Developing a good profile is a balancing act for the process engineer, who also needs to make sure smaller and temperature-sensitive components do not overheat or become damaged. The solder joint on a given PWBA that is the last to reach minimum soldering temperature (typically on or underneath one of the components with the highest thermal mass) determines the temperature profile setting for a given PWBA and soldering process/machine. As a practical matter, minimum soldering temperature is somewhat (~ 25 ☌) above the liquidus temperature of the solder alloy. Metallurgical bonding requires that the surfaces to be soldered and the solder reach this minimum soldering temperature for a sufficient time to allow wetting of the solder surfaces and the formation of a layer(s) of intermetallic compound(s) of some of the base metal(s) with one or more constituents of the solder alloy. Minimum soldering temperature is the minimum temperature necessary to ensure metallurgical bonding of the solder alloy and the base metals to be soldered. This standard is for managers, design and process engineers and technicians who deal with mass soldering processes.īackground During mass soldering, it is important that all solder joints reach the minimum soldering temperature. Purpose The purpose of this standard is to provide useful and practical information for developing thermal profiles to produce acceptable SnPb and Pb-free electronics assemblies. time plot for each fully populated printed wiring board assembly (PWBA), using thermocouples attached with high-temperature solder or copper or aluminum tapes to selected representative components of the PWBA as it travels at a given belt speed (i.e., transport speed) through various temperature zones of an oven or soldering system. Thermal profile is a unique temperature vs. This standard describes thermal profile guidelines and practical guidelines to meet requirements to produce acceptable solder joints in mass soldering processes, including but not limited to reflow and wave soldering. IPC-7530A Guidelines for Temperature Profiling for Mass Soldering Processes (Reflow and Wave) ![]() The revision also includes a full-color troubleshooting guide for addressing common defects which can be attributed to profiling. This IPC-7530A revision expands the focus of the original standard from reflow profiling to include profiling for vapor phase, laser, selective soldering and wave soldering. This IPC-7530A standard provides useful and practical information for developing thermal profiles to produce acceptable SnPb and Pb-free electronics assemblies.
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