Views:26 Author:Site Editor Publish Time: 2021-02-22 Origin:Site
Lead-free PCB assembly fabrication refers to a custom PCB assembly that does not use lead at any stage of manufacturing. Traditionally, lead is used in the PCB soldering process. However, lead is toxic and therefore harmful to humans. Considering its consequences, the EU Restriction of Hazardous Substances Directive (RoHS) prohibits the use of lead in PCB assembly fabrication. Substituting a less toxic substance for lead has almost no difference in the PCB assembly fabrication process. This article introduces the lead-free PCB assembly fabrication process in detail step by step.
Lead-free PCBA guide
The lead-free custom PCB assembly fabrication process is divided into two basic parts, namely the pre-assembly process and the active assembly process. The steps involved in the lead-free PCB assembly fabrication process are as follows.
These steps form the basis for error-free and accurate PCB assembly. The pre-assembly steps for lead-free PCB assembly are as follows.
The manufacturer uses the finished lead-free PCB as the prototype. This can be a normal operating PCB, an invalid PCB or a dummy component. Use the assembled template to trace through the contour. Compare the lead-free component design with the prototype to ensure its compatibility with the component.
Solder paste inspection:
Since the IPC-610D standard checks PCB size and solder paste to ensure that lead-free solder joints have a metallic appearance, which is very different from lead-based solder, it is very important to conduct inspections. Moisture content is also tested in, because the circuit board is exposed to high moisture content in lead-free soldering compared to traditional soldering methods.
Bill of Materials (BOM) and component analysis:
During this process, customers must verify the bill of materials (BOM) to ensure that the components are made of lead-free materials. Lead-free components are susceptible to moisture, so manufacturers should bake them in an oven. Once the necessary methods have been implemented, the actual lead-free assembly begins.
Active assembly steps
During the active assembly process, PCB assembly was carried out. The steps involved in active lead-free assembly are as follows.
Template placement and solder paste application:
In this step, the lead-free template at the forming stage is placed on the board. Then apply lead-free solder paste. Generally, the lead-free solder paste material is SAC305.
The placement of components can be done manually or using automatic machinery. This is a placement and placement operation, but the components used need to be confirmed and marked during the BOM verification stage. The machine or operator selects the labeled components and places them in the designated locations.
Perform lead-free through-hole or manual soldering at this stage. No matter which process is used, THT or SMT, soldering must be lead-free.
Circuit board placement in the reflow oven:
RoHS-compliant PCB requires high-temperature heating to evenly melt solder paste. Therefore, the PCBs are placed in the reflow oven, where the solder paste is dissolved. Then, the board is cooled with solder paste melted with a curing agent under this next cooling. Fix the component in its place.
Testing and packaging:
The PCB has been tested in accordance with the IPC-600D standard. In this step, the solder joints are tested. The visual inspection is followed by AOI and X-ray inspection. Perform physical and functional tests before packaging.
To ensure the packaging of lead-free PCBs, it is very important to use anti-static discharge bags. This is to ensure that the final product does not cause static electricity during transportation.
Giant is a custom PCB assembly fabrication manufacturer that uses RoHS-compliant FR4 materials for PCB manufacturing. If you need custom PCB assembly, please contact us now.