Delamination in Flex PCB Boards

Delamination in flex pcb board occurs when the layers separate from one another. The cause of this is usually poor adhesives or moisture, and can lead to failure of the circuit board. To prevent delamination, it is important to understand the causes and take steps to avoid them. In this blog post, we will discuss effective strategies and industry best practices for preventing rigid-flex delamination.

A key factor in preventing flex circuit delamination is the thickness of the adhesive used to bond the copper layers together. Manufacturers have a number of options for fabricating a flex circuit, including photoimageable (PI) and conductive epoxy. The PI process is a good choice for tight geometries that don’t lend themselves to drilled coverlay processing. PI is also available in thin film versions that allow for thinner designs.

Another way to prevent flex PCB delamination is to ensure that the bending radius of the PCB is large enough to avoid damage to the copper layers. The minimum bend radius is a critical design factor for any flex circuit, and should be specified during the layout phase of a new circuit board.

The bending radius is also important for the design of plated through-holes and the placement of components in the circuit board. A common mistake is to place conductors closer together than needed, which increases impedance and reduces signal speed. The correct spacing allows the copper to conduct properly, while minimizing strain and stress.

How to Prevent Delamination in Flex PCB Boards

A third factor in preventing flex circuit delamination involves the baking procedure after assembly. A standard practice is to bake the flex circuits before soldering, which helps eliminate any residual moisture that could cause delamination. Unlike rigid PCBs, flex circuits require longer bake times to remove moisture and reduce the risk of delamination.

Moisture is the most common cause of flex PCB delamination. When a flex circuit is exposed to high temperatures during solder reflows, the entrapped moisture can boil and delaminate the layers of the circuit. This can be violent, literally blowing the flex circuit apart, or mild, with small blisters that may later develop into more serious delaminations.

A fourth method for preventing flex circuit delamination is to identify and inspect the circuits regularly. This helps detect delamination early, allowing for quick repair before it becomes a serious problem. Nondestructive testing methods, such as x-rays and thermography, can help identify areas of potential delamination. Detecting delamination early allows the fabricator to take steps to correct the issue before it affects the function of the circuit.

If you have concerns about delamination in your flex PCB, contact PCBWay. We can do an electrical test of your flex circuits to make sure everything went well during manufacturing. We can also add what’s called a stiffener to selected areas of your flex circuit, which is a rigid material such as FR4 that’s added to certain areas of the flex circuit to increase its overall thickness. This can help prevent stress and fractures from conductor stress points, but it does come at an extra cost.