The focus of SMT process control mainly revolves around the 5Ps: PCB (Printed Circuit Board), Parts, Paste (solder paste), Placement, and Profile curve. This encompasses material control, printing design (including template design and printing control), patch control, and temperature curve design.
1.1 Material Control
PCB (Printed Circuit Board) stands as the cornerstone material. Upon receipt, verification of the manufacturer’s COC (Certificate of Conformance) is essential. This includes scrutiny of the metallographic section report, pad solderability report, and cleanliness test. Additionally, flatness testing is conducted. Prior to assembly, pre-drying is imperative to expel moisture from the board. Attention must also be given to the PCB’s expiration date.
The components must ensure good solderability of the pins by removing gold treatment. Components requiring secondary screening must also maintain coplanarity due to susceptibility to deformation from test fixture clamping, potentially causing poor coplanarity.
1.2 Printing Design
Prior to printing, template design is crucial. This involves determining pad openings, template thickness, and processing method, typically stainless steel laser cutting with inner wall electropolishing. Upon template delivery, tension testing to 40-50 N is necessary. Tension should also be checked before each use, ensuring it remains above 30 N after repeated use.
Once the template is finalized, factors influencing print quality include solder paste quality and printing process parameters. Testing and verifying solder paste, controlling re-temperature, ensuring thorough stirring, and adhering to time limitations are essential.
Squeegee pressure in process parameters relates to squeegee size, requiring 1.97 ~ 2.76 N/cm. Printing speed is influenced by solder paste composition and pad pitch.
1.3 Placement Control
For chip components, checking pin coplanarity is crucial, typically set at 0.08 ~ 0.12 mm. Mounting pressure should ensure component leads press into solder paste to at least half the pin thickness. Caution is needed with fragile glass package devices to minimize mounting pressure and prevent damage.
1.4 Temperature Profile Design
Reflow soldering temperature profiles require actual testing for each PCBA type. A well-designed profile ensures the entire board reaches thermal equilibrium, with preheating temperatures balancing maximum and minimum heat capacities.
Temperature profile settings depend on PCBA size, layer count, component specifications, pin plating, and solder characteristics.
1.1 Material Control
PCB (Printed Circuit Board) stands as the cornerstone material. Upon receipt, verification of the manufacturer’s COC (Certificate of Conformance) is essential. This includes scrutiny of the metallographic section report, pad solderability report, and cleanliness test. Additionally, flatness testing is conducted. Prior to assembly, pre-drying is imperative to expel moisture from the board. Attention must also be given to the PCB’s expiration date.
The components must ensure good solderability of the pins by removing gold treatment. Components requiring secondary screening must also maintain coplanarity due to susceptibility to deformation from test fixture clamping, potentially causing poor coplanarity.
1.2 Printing Design
Prior to printing, template design is crucial. This involves determining pad openings, template thickness, and processing method, typically stainless steel laser cutting with inner wall electropolishing. Upon template delivery, tension testing to 40-50 N is necessary. Tension should also be checked before each use, ensuring it remains above 30 N after repeated use.
Once the template is finalized, factors influencing print quality include solder paste quality and printing process parameters. Testing and verifying solder paste, controlling re-temperature, ensuring thorough stirring, and adhering to time limitations are essential.
Squeegee pressure in process parameters relates to squeegee size, requiring 1.97 ~ 2.76 N/cm. Printing speed is influenced by solder paste composition and pad pitch.
1.3 Placement Control
For chip components, checking pin coplanarity is crucial, typically set at 0.08 ~ 0.12 mm. Mounting pressure should ensure component leads press into solder paste to at least half the pin thickness. Caution is needed with fragile glass package devices to minimize mounting pressure and prevent damage.
1.4 Temperature Profile Design
Reflow soldering temperature profiles require actual testing for each PCBA type. A well-designed profile ensures the entire board reaches thermal equilibrium, with preheating temperatures balancing maximum and minimum heat capacities.
Temperature profile settings depend on PCBA size, layer count, component specifications, pin plating, and solder characteristics.
