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Graping
Graping is a phenomenon marked by the appearance of unreflowed solder particles on top of the solder mass. The solder that is partially coalesced looks like a cluster of grapes which is where the phenomenon’s name is derived.〔(" Present and future solder technologies: how new powders, activator chemistries and epoxy fluxes are evolving for production use." )〕
== Causes ==
Graping occurrence has continued to increase since it was first identified in 2006. The viscosity of the flux decreases as the temperature of the reflow oven increases. Lead-free reflow soldering temperatures are higher which results in more graping. Graping is also caused by increased surface oxidation. The increased surface oxidation is the result of smaller printed paste deposit volumes that cause a diminished surface area to flux ratio of the solder particle resulting in flux exhaustion. While solder paste can be manufactured using any size range however there has been a move towards finer particle sizes especially for fine feature stencil printing.〔(" Solder paste basics" )〕 Finer particle sizes places added pressure on the solder paste flux to remove surface oxides which leaves the outside of the joint not fully coalesced producing the irregular surface finish known as graping.〔〔(" Best Practices Reflow Profiling for Lead-Free SMT Assembly" )〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Graping」の詳細全文を読む
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