A solder ball valve can act as a connector between multiple chip stacks in a PCB. It can serve to regulate the flow of electrons and signals between the various layers of the pile. Solder ball valves are usually contained in a Ball Grid Array (BGA). A BGA usually provides more inter-connectivity than a dual in-line or flat package.
Here are some of the causes of solder balls.
The presence of moisture in your solder paste can cause solder balls to explode during reflow. Water seeps into the solder paste during refrigeration.
If the paste does not attain room temperature after removing it from the refrigerator, it will soak up the moisture. However, you can eliminate the water by baking.
The board itself can bring about undesired solder balls during hand soldering. Air, moisture, or alcohol used to clean the board can make the board yield unwanted solder balls.
These contaminants can creep in between layers, open vias, and through-holes of a board with cracked or incomplete plating. Moreover, when the board undergoes heating in reflow, these contaminants are forced out. Their abrupt escape shoots gases in all directions and consequentially blows liquid solder across the board. Paste flux gases may also produce this effect when they escape from the sections of the panel close to the surface.
If your board admits contaminants through open edges and vias cracks, and through-holes, there isn’t much hope. You’ll most likely need to remake the board, as you can’t bake the trapped air away. If paste gasses are jetting off from underneath the board, you can resolve this by reducing the amount of paste. You can also fix this by minimizing the amount of volatiles in the paste.
Your stencil might be depositing solder paste discriminately. You need to ensure that the under stencil cleaning process you use is efficient and thorough-going.
It could be that you’re using an inappropriate under stencil wiping roll, which is too thick. The improper thickness of the registration can cause the balls to spread across the underside of the stencil. Moreover, when you eventually use the stencil on a PCB, the extra balls get deposited on the board.
Inappropriate Solder Paste Formulation
Poorly formulated solder pastes may explode during heat reflow and blow liquid solders randomly across the board. The volatile materials are usually the most likely causes of the explosion.
In such cases, you can prevent such explosions by reducing the preheat ramp rate. That allows the volatile material to be pushed out without abrupt outgassing. However, you need to ensure that you preheat slow enough.
The Best Troubleshooting Technique For Solder Balls that Occur During Hand Soldering
The best way to find out the causes of solder balls during hand soldering is to test multiple products. The aim is to check to see if the defect occurs in certain types of PCB. Run various boards with the same solder paste and equipment to pinpoint the exact variables from which the fault originated.