Professional PCB Assembly

After the PCB is transferred to the printing station via the automatic PCB loader, the stencil (custom-designed based on PCB layout) achieves precision alignment with the PCB. The squeegee then prints solder paste onto the pads.

Key parameters

Solder paste thickness (<15μm)

Printing offset (<10% of stencil aperture width)

Real-time inspection is performed by SPI (Solder Paste Inspection system), with non-conforming boards automatically rejected for rework.

The pick-and-place machine utilizes vision alignment (CCD camera) to identify PCB fiducial marks and component positions, achieving a placement accuracy of ±0.030mm (placement accuracy for QFP components). It mounts them onto preprogrammed pad locations.

Supports multiple component types:

Passive components (resistors, capacitors)

Active components (ICs, chips)

Odd-form components (connectors)

High-speed placement rate reaches >100,000 components per hour (CPH).

The assembled PCBs enter the reflow oven and go through four stages: preheating (150-180°C), soaking (to prevent component damage), peak temperature (approximately 245°C for lead-free solder paste), and cooling. This process melts the solder paste and forms solder joints.

The temperature profile must comply with the IPC-J-STD-001 standard to ensure good solder wetting (wetting angle < 90°). After soldering, AOI (Automated Optical Inspection) is used to check for defects such as cold solder joints and bridges. For sensitive components requiring reflow temperature adjustment, low-temperature solder paste should be used for low-temperature assembly.

For through-hole components that cannot be surface-mounted (such as high-power connectors and electrolytic capacitors), they are inserted into the PCB through-holes either manually or by automatic insertion machines, followed by wave soldering to complete the welding process (suitable for mass soldering of DIP components).

Visual inspection

AOI (Automated Optical Inspection) or manual review is performed on the appearance of solder joints and components, with a focus on checking for solder balls and component misalignment.

Electrical testing (if required)

ICT (In-Circuit Test) is used to check circuit continuity and component parameters; FCT (Functional Test) simulates actual operating conditions to verify overall performance (such as signal transmission and voltage output). For complex boards, X-RAY inspection is required to examine hidden solder joints such as those of BGA components.

Conforming products are packaged in anti-static packaging (anti-static bags, trays) as required by the customer, accompanied by test reports (including AOI/X-RAY images and ICT/FCT data).

Batch information is recorded through the MES system to achieve full-process traceability.