What is Blow Hole

A blow hole, also known as a pin hole, is a defect that can occur during the soldering process. It is characterized by the escape of moisture trapped within the board, which turns into water vapor and gasses through either thin copper plating or voids in the plating. Blow holes are particularly common in class 2 and class 3 boards.

During the wave soldering process, the moisture inside the board undergoes a phase change, transforming into steam and building up pressure. This pressure eventually causes the steam to erupt through the wall of the plated through-hole, resulting in a blow hole. Poor plating in the holes can exacerbate the problem.

Blow holes can weaken solder joints and become a potential cause for failure in the PCB. To mitigate this issue, it is recommended to bake the boards in an oven at 120°C for 4 hours to reduce the amount of moisture in the board. If blow holes persist even after baking, it may be necessary to increase the bake time.

In addition to moisture, blow holes can also be caused by components capping the top of the plated through-hole, which traps the flux. When subjected to the wave soldering process, the flux outgasses and builds pressure until it blows the solder out of the hole. To prevent this, components must have a standoff to avoid capping the plated through-hole.

Frequently Asked Questions

What Causes Blow Hole and Porosity

Blowhole and porosity are caused by the entrapment of gas during the solidification of molten weld metal. These cavity-type discontinuities or pores can reduce the strength of a weld. In arc welds, porosity is typically caused by dissolved gases that are commonly found in molten weld metal.

What Is Blow Hole in Manufacturing Technology

A blowhole in manufacturing technology is a term used to describe a cavity that is formed within a die cast product. This occurs during the die casting process, where molten metal is injected into a mold cavity and subsequently cools and solidifies.

What Is the Reason for Blow Holes

A blowhole is a flaw that can occur in a soldered joint on a printed circuit assembly that includes plated through-hole circuitry. Blowholes are typically caused by the generation of volatiles within the through-hole during the soldering process. It is commonly believed that these volatiles originate from the flux used in the soldering process.