Reflow soldering issues

Q1. If I go to the Pb-free solder paste, is it necessary that I have to change my reflow oven OR just by changing with respect to solder paste specification, I can reach my goal? A1. It depends on your current oven. Some ovens can meet the higher temperature requirements of LF, other can not. If you talk to sale-types, they�ll tell you that you need eight zones and be jet propelled.

Q2. What is the �Low- Temperature Phase� in any solder paste alloy? A2. This usually refers to a solder alloy that contains bismuth [Bi]

Q3. What is the meaning of �Time Above Liquidous (TAL)�? What is beneficial, minimum TAL or maximum TAL? A3. Look here http://en.wikipedia.org/wiki/Reflow_soldering

Q4. What is the use of solder powder and solder spheres in the production assemblies? A4. Solder powder or sphere is the shape of the solder alloy in solder paste formed by the paste fabricator. The balls are suspended in mixture with flux.

Q5. Sometimes what happens under inspection, fillet of components are excellent but they are failed in electrical testing, after retouching PCBs are passed? Why? A5. Sometimes solder connections can be damaged by improper handling or by the impact of the pins of the test head.

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