![]() The Peak temperature (Tp) for the reflow profile, measured at top of the package. This varies according to the used solder alloy. Liquidous temperature (TL) for lead-free soldering - this is approximately 217☌. Insufficient solder results in deficient capacitor adherence to the printed wiring board, which may cause capacitor dropout or poor electrical connection which, in turn, may cause reliability to deteriorate. solder paste is starting its activity and cleaning process of all surfaces involved into the later solder joint begins. As a result, cracking or breaking of the capacitor may occur. This three step profiling approach has been commonly used since the early days of SMT. A typical profile consists of three heating slopes (the time vs temperature relationship or rate of temperature rise) defined by Figure 3-1. Use a suitable amount of solder to form a proper fillet shape.Įxcess solder generates high contraction stress and thermal stress. The reflow profile is defined by the relationship of temperature versus time during heating. If the interval between applying solder paste and mounting a capacitor is too long, solderability may decrease due to drying and hardening of the solder paste. providing equal heating to both terminations during soldering Mount the capacitor as soon as possible after applying solder paste. The tombstone phenomenon can be avoided by taking the following measures: It’s not suitable for large components, and it’s not meant for power electronics. ![]() It can solder large components that require solder with a high melting point. ![]() It’s less cost-effective and can be much slower than wave soldering. Take into consideration tombstone phenomenon (also called "Manhattan phenomenon")įor 3216M size or smaller capacitors when the soldering is not proper. It’s faster and more cost-effective than reflow soldering. When the capacitors are soldered under long duration or high temperature, the dissolution of electrode (leaching), deterioration of adhesion (shear strength) and capacitance decrease may occur. EFD Inc., 14 Blackstone Valley Place, Lincoln, RI 02865 U.S.A. NOTE Lead-free solder has a higher liquid phase temperature than eutectic solder (Sn-Pb).Ĭonfirm the heat resistance of the capacitor in regards to soldering temperature in advance. Appropriate modification of one or more of these process variables will reduce or eliminate tombstoning.
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