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.

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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

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 much larger should a plated-through hole be than lead diameter to get good solder wetting?

I’m designing a new PCB where I have a whack of connectors that have to line up with the metalwork. There are some problematic connectors. All 4 pins are round. I want to have the holes as small as possible while allowing for good solder adhesion over the full length of the pin. I’m looking for guidance on how much clearance around the component lead I should have in order to get good solder wetting and adhesion.

Oliver Smith December 4, 2023

How can I mount a pulse oximeter on the surface of PCB without putting too much stress?

The PCB has a pulse oximeter mounted on the surface, and it’s tolerance is 0.6mm. The problem is the pulse oximeter needs to touch the bottom case at all times. How to best mount the PCB in the case without putting too much stress on the pulse oximeter? Will screws with flexible washers be all right? Sadly separating pulse oximeter from main PCB is not an option.

Oliver Smith December 5, 2023

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

Oliver Smith

Oliver Smith

What Others Are Asking

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?

How much larger should a plated-through hole be than lead diameter to get good solder wetting?

How can I mount a pulse oximeter on the surface of PCB without putting too much stress?

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