Apr. 12, 2019
SMT solder paste inspection of the main content of metal content, solder ball, viscosity, metal powder oxide content. Then what materials are tested in PCBA processing and assembly process? The following China PCB Manufacturer Shengxu Electronics to share PCBA assembly process material content.
1. Metal content. In the application of SMT, the metal content in solder paste is usually required to be 85%~92%, and the commonly used detection method is described below.
(1) take the paste sample 0.1g into the crucible.
(2) heat crucible and solder paste.
(3) solidify the metal and remove the solder residue.
(4) weighing metal weight: metal content = metal weight 100% solder paste weight.
2. Solder balls. Common solder ball detection methods are described below.
(1) in the center of alumina ceramic or PCB substrate coating diameter of 12.7mm, thickness of 0.2mm solder paste graphics.
(2)The sample according to the actual assembly conditions for drying and reflow.
(3) solder curing inspection.
3. Viscosity. The typical viscosity of solder paste used in SMT is 200~800Pa•s, and the main factors influencing it are flux, metal content, metal powder particle shape and temperature. Generally, rotary viscosity agent is used to measure the viscosity of solder paste.
4. Metal powder oxide content. Professional Printed Circuit Board Factory thinks that metal powder oxidation is the main factor of forming solder balls. Auger analysis can be used to quantitatively detect the content of metal powder oxides, but it is expensive and time-consuming. The following methods are often used for the qualitative determination and analysis of metal powder oxide content.
(1) take 10g solder paste in a crucible filled with enough peanut oil.
(2) in the 210 ℃ heating furnace heating and solder paste to flow again, during the peanut oil extraction flux from the solder paste, flux cannot clean oxide from the metal powder, as well as prevent during heating and reflow additional oxidation of metal powder.
(3) remove the crucible from the furnace, and add appropriate solvent to dissolve the remaining oil and flux.
(4) remove the solder from the crucible, visual measurement can be found on the metal surface oxide layer and degree of oxidation.
(5) estimate the ratio of oxide coating, the ideal state is no oxide coating, generally requires no more than 25% oxide coating.
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