Most solder paste manufacturers correct these issues by adjusting the formulas for Type 4 and 5 solder pastes. This is due to a higher potential for oxidation of Type 4 and 5 solder powders. Type 4 and 5 solder pastes can generate more random solder balling and graping than Type 3 with certain solder paste formulations. The shelf life of Type 4 and 5 solder paste is typically shorter than Type 3 due to a higher rate of reaction between the flux and solder powder. This higher rate of reaction leads to potential issues when using Type 4 and 5 solder pastes. Therefore, smaller solder powders react more quickly than larger solder powders. The rate of chemical reaction with the solder powder is directly proportional to the surface area of the solder powder. For the same mass of solder powder, the surface area of Type 4 solder powder is roughly 20% higher than Type 3, and the surface area for Type 5 solder powder is roughly 75% higher than Type 3. ![]() The surface area of the smaller solder powder types is significantly higher than the larger solder powder types. Smaller solder powder sizes like Type 4 and Type 5 give improved printability but also can create some issues due to chemical reactions with the solder powder. This combination allows for printing of even the finest of components. The increase in transfer efficiency is dramatic when Type 4 or 5 solder pastes are used along with fine grain steel stencils coated with NanoSlic Gold. ![]() Fine grain laser cut steel stencils along with NanoSlic Gold coating give a substantial increase in transfer efficiency as compared to standard steel stencils. This is especially true when these solder pastes are coupled with stencil technologies designed to enhance printing. Type 4 or 5 solder pastes enhance printing for miniaturized components. At smaller area ratios this difference in transfer efficiency becomes less distinct. In general, Type 5 gives higher transfer efficiency than Type 4 solder paste, and Type 4 gives higher transfer efficiency than Type 3 solder paste.
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