FAQS

A1: Incomplete or excessive etching, drilling deviation causes the inner copper foil to fracture ‌.
Solder bridging or substrate layering ‌.
‌ Countermeasures ‌
The etching parameters were optimized and calibrated with a high precision LDI exposure machine and X-ray alignment system ‌.
Strengthen substrate quality control to avoid uneven laminating stress ‌5.

A2: Pad oxidation, insufficient welding temperature, low flux activity ‌13.
Solder paste printing or uneven thickness (SMT process).
‌ Countermeasures ‌
Choose between gold sinking or ENIG surface treatment process, using nitrogen to protect the welding environment ‌.
Calibrate steel mesh design parameters (e.g. hole size, scraper pressure) ‌.

A3: Impedance mismatch, crosstalk between adjacent signal lines ‌.
‌ Countermeasures ‌
The line width/pitch (e.g., 50Ω impedance matching) is optimized by simulation and shielded by differential wiring or ground wire ‌.

A4：High power components lack heat dissipation and substrate glass transition temperature (TG value) is low.
‌ Countermeasures ‌
Add heat dissipation holes or metal substrate (such as aluminum substrate), and select high temperature resistant material with TG≥170℃ ‌.

A5：Uneven lamination stress and moisture absorption lead to material expansion ‌35.
‌ Countermeasures ‌
The pressing temperature curve was optimized and the substrate was roasted for dehumidification (120℃/2h) before production.

A6：Component misalignment, ball residue, reverse polarity, or error ‌.
‌ Countermeasures ‌
AOI testing equipment was used to check component offset and optimize reflow temperature curve ‌.

A7：Substrate delamination, green oil foaming/shedding, surface oxidation ‌5Countermeasures ‌
Select a highly reliable substrate (such as FR-4) and strictly control the solder stop coating process ‌.
Sum up
Circuit board problems are mainly concentrated in three aspects: design, manufacturing process and material selection. Yields and reliability can be significantly improved ‌ by optimizing parameters (such as etching accuracy, welding temperature), upgrading equipment (such as X-ray calibration systems), and selecting high-performance materials (high TG value substrates, gold settling processes). SMT and other assembly links need to be combined with automated inspection technology (such as AOI) to realize the whole process monitoring ‌.

A8: Prepare for welding ‌
‌ Components and PCB processing ‌

Check whether the pins of the components are oxidized or deformed. Use sandpaper or special detergent to remove the oxidized layer, and ensure that the welding surface is clean ‌.
Chemical cleaning or mechanical polishing of the PCB pad to ensure that the surface is smooth and pollution-free, and check the integrity of the solder mask ‌.
‌ Materials and tools of choice ‌

Use eutectic solder wire with 63% tin content and moderate activity flux to avoid residue corrosion circuit ‌25.
Select the power of the soldering iron according to the component type (such as 20-30W for small components), and ensure that the soldering iron tip is clean ‌.
Two, ‌ process parameter control ‌
‌ welding temperature and time ‌

Control the temperature of the electric iron at 300-350℃, high-precision components need to use a temperature control iron to reduce thermal damage ‌35.
It is recommended that the single point welding time is 2-3 seconds to avoid virtual welding or oxidation caused by too short time ‌.
‌ solder dosage and operating stability ‌

Accurately control the printing amount of solder paste, and the opening size of steel mesh should match the components to avoid printing leakage or excessive thickness ‌.
Keep the hand stable and the soldering iron tip in full contact with the pad during welding to prevent tin beads or bridge ‌.
Iii. ‌ Design and process optimization ‌
‌PCB design and surface treatment ‌

Optimize pad size and spacing design and ensure uniform film thickness (0.2-0.5μm) ‌ when using OSP surface treatment.
Use differential routing or ground shielding for high-density wiring areas to reduce signal interference ‌.
‌ Environment and Quality Control ‌

Nitrogen is used to protect the welding environment and reduce oxidation risk. Pre-bake the substrate (120℃/2h) to remove moisture ‌.
Use AOI equipment to check solder joint quality, focusing on welding defects, short circuits and component offset

Targeted prevention of common problems ‌
‌ virtual welding/fake welding ‌ : strengthen storage control of components (sealed and moisture-proof). Dry them before welding ‌.
‌ tin bead/short circuit ‌ : clean welding area impurities, adjust solder flow and reflow temperature curve ‌.
‌ pores/pinholes ‌ : Ensure that the copper plating of PCB through holes is ≥20μm, and pre-bake the sheet ‌ if necessary.
Sum up
The prevention of bad welding should be started from ‌ material selection ‌ (high-quality solder paste, adaptive flux), ‌ process control ‌ (temperature/time parameters, operation specifications) and ‌ design optimization ‌ (pad layout, surface treatment), combined with automatic inspection (such as AOI) to realize the whole process monitoring ‌.