PCB Fabrication Assembly During Bending
Printed circuit boards are designed to offer an ideal surface for mounting components that will allow for the electrical transmission of signals throughout the board. They’re also designed to be flat, allowing them to bend easily in one or more directions without compromising the integrity of the connections between layers. However, PCBs can suffer from a number of issues that affect their ability to function properly. One such issue is warpage, which can occur when the boards are bending along one or more axes. This is a serious problem that can lead to a variety of other problems, including the failure of solder joints and power shorts. If you’re worried about your PCBs developing this problem, there are steps you can take to prevent it from occurring.
During the manufacturing process, PCBs have copper applied to precise areas on the panel. To ensure that the copper doesn’t cause damage to the board, a protective layer called dry film is placed over it. This layer is then exposed to a tin plating bath, resulting in tin covering the copper in those precise locations. After the tin is removed, a chemical stripping process removes any remaining dry film and tin. This step also protects the copper from corrosion during storage and shipping.
The tin/copper coating on the pcb fabrication assembly surface prevents oxidation and provides a protective layer for the copper traces, pads, and other features that will be covered in solder. The tin/copper coating also makes it possible to conduct current through the traces. The tin/copper coating can be damaged by mechanical stress, such as that caused during bending. In order to prevent this, the tin/copper coating must be protected by an epoxy resin, which is cured with heat.
Preventing Warpage in PCB Fabrication Assembly During Bending
When a PCB is subjected to a significant amount of force, such as being dropped or being bent, the copper on the board will expand and contract at different rates. If the traces are not evenly distributed, this can result in a warp pattern that’s amplified during the reflow/soldering stage. To prevent this, the substrate should be thicker and copper percentages should be closely monitored to avoid uneven expansion.
Another common problem is the cracking of BGA solder joints. This happens when the solder joint is unable to withstand the stresses that come with the rapid rise and fall in temperature during the reflow process. Fortunately, this is an easy fix by using a stronger adhesive to attach the component and ensuring that the component isn’t located too close to the solder joint.
Similarly, to prevent cracking, it’s crucial that the pallet on which the PCB is placed during the assembly and reflow process is sturdy enough to support the weight of the component. The pallet should also be properly spaced to allow for proper airflow between the component and the other PCBs on the plate, which will help prevent thermal stresses that can crack solder joints. You can also minimize the risk of flex cracking by making sure that your traces aren’t located too close to a stiffener or anchor.
