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Incoming Inspection Of PCBA Assembly Process Materials (part I)

Mar. 19, 2019

SMT solder paste inspection of the main content of metal content, solder ball, viscosity, metal powder oxide content. Then in the PCBA from PCBA Supplier Processing and assembly process, what materials are tested by incoming materials? The following to share with you 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 percentage content = metal weight solder paste weight x 100%.

2. solder ball. The commonly used 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.

The sample according to the actual assembly conditions for drying and reflow.

(3) solder curing inspection.

SMT PCBA Processing

SMT PCBA Processing

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. The measurement method can be seen in the description of relevant test equipment.

4.Metal powder oxide content. Metal powder oxidation is the main factor in the formation of 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) take out 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.