How do PCB manufacturers prevent solder from entering vias during wave soldering?

I have some PCBs that were wave soldered but the vias still remain open, they are not filled nor plugged form what I can see. I do not see any solder on the annular rings of the vias either. How do they go about doing so?

November 3, 2023

Choose the right flux. There are many reasons for welding balls, but flux is the main reason.

Generally speaking, fluxes with low solid content tend to form solder balls when the underside SMD elements require double PCBA wave soldering. Because these additives are not designed to be used for long periods of time. If the flux sprayed on the PCB has been used up after the first wave crest, there is no flux after two peaks. Thus, it cannot play the function of flux and help reduce tin balls.

One of the main ways to reduce the number of welding balls is to choose a flux that can withstand longer periods of heat.

#PCB Assembly

Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.

Oliver Smith

What Others Are Asking

Do the scratches on the PCB have any bad effect to products?

We receive a batch of PCB with scratches from my supplier, but they think it is acceptable. I have never seen such error on even an B stock boards parts. Very confused. How do scratches affect PCB working?

Oliver Smith October 13, 2023

How do you usually organize SMT parts during PCB assembly?

Suppose one is hand-assembling a board with many SMT components. Unlike THT, SMT components are often not labeled. How might one keep small (<100) quantities of such parts properly organized during assembly? Are there particular tools? Storage devices? Methods?

Oliver Smith November 22, 2023

Are there any guidance on recommended package size and type for a surface mount linear regulator IC on my board that will be hand-soldered?

I am designing a board that needs a couple linear regulators (5.5v to 3v and 3v to 1.6v) but I am having difficulty selecting a suitable surface mount package type and size that will allow me to hand solder the IC to the PCB without too much difficulty.

Oliver Smith December 4, 2023

How do PCB manufacturers prevent solder from entering vias during wave soldering?

Oliver Smith

Oliver Smith

What Others Are Asking

Do the scratches on the PCB have any bad effect to products?

How do you usually organize SMT parts during PCB assembly?

Are there any guidance on recommended package size and type for a surface mount linear regulator IC on my board that will be hand-soldered?

Read Detailed Advice From Blog Articles