How to Make PCB More Reliable?

Whether the printed circuit board is housed in a water analyzer, spacecraft, or aircraft, the cost of failure can be easily measured—in terms of lives or dollars lost. For these cases, Singo recommends that designers pay special attention to the design choices they make. This is due to high-reliability engineering combined with good design practices, especially when PCBs must operate in harsh environments.

The PCB is likely manufactured by a certified facility, and the manufacturer has assigned an employee to be responsible for ensuring that the board meets or exceeds expectations in all aspects of the design. This may include flatness, surface finish, plating thickness, etc. Since these are measurable quantities, it is easy to check that the board meets the requirements.

Once the customer accepts the board after delivery, the manufacturer's responsibility for the quality of the board usually ends. On delivery, customers expect all boards to perform as they designed them.

However, reliability covers the entire life cycle of a product and is a more difficult metric to quantify. This is because several factors can affect reliability, including material variability, manufacturing process control, and PCB design. Also, board failure dates vary and are often unknown.

Even if the designer follows all best practices and the manufacturer executes all processes flawlessly, the manufactured PCBs will often vary slightly due to material differences. To this variability, when coupled with poor process control and/or poor design choices, a PCB can contain latent defects.

Unlike quality, which is easy to define—whether the board meets specifications—defining reliability is not easy, because it is difficult to predict whether a PCB will fail within a year, within five years, or after a lifetime of up to 10 years. Singo provides some design tips that will help improve PCB reliability to a great extent.

For an electronic device to function properly, all electronic components must remain connected to each other. For example, in an IC, a silicon chip must remain connected to a metal lead frame by bonding wires. The leadframe must remain connected to the copper pads on the PCB through solder, and the copper pads must remain connected to each other through vias, copper pours, and traces. In a high-reliability board, all of these connections must remain intact throughout the life of the device.

When the temperature of a component or the board itself increases, they expand at different rates based on its coefficient of thermal expansion (CTE). For PCBs, the CTE is anisotropic, which means that the expansion along the length (X and Y axes) is different than the expansion along the width of the PCB (Z axis). This uneven expansion can crack the via barrel in the PCB, rendering it inoperable. Therefore, Singo recommends that designers use materials with matching CTEs, where the expansion of the copper will match that of the PCB material.

Open holes near pads can cause two types of failures. Open vias trap contaminants such as flux that can slowly corrode the copper over time, causing disconnects. Another problem with open vias is that they can cause the solder to dislodge. Molten solder from nearby pads flows into the via, leaving little solder to make a proper bond between the pad and the component. Singo recommends filling the vias with a conductive or non-conductive material to prevent such failures.

Boards with SMDs go through a soldering process called reflow, while boards with through-hole components go through wave soldering. For both soldering methods, there is a need to find the optimum heat distribution for the board to follow as it passes through the soldering machine.

For soldiers with lead and tin components, the melting point is low enough to allow enough time for the board to heat up and allow the solder to flow. However, with the implementation of the RoHS directive, the electronics industry must use solders that do not contain lead.

This requirement to remove lead from solder has resulted in solder compositions with higher melting temperatures. Designers must now use PCB materials that can withstand these higher temperatures without damage. In addition, the thermal profile of lead-free solder must now allow the board to reach the required higher temperature, but for a shorter period of time.

To comply with the RoHS directive, Singo recommends that assemblers use suitable lead-free solders and pastes when assembling circuit boards, and adjust the time and temperature settings in the soldering machine to set the proper heat distribution. An optimal thermal profile should be able to reliably solder both the heaviest and smallest components on the board.

In order to make reliable RoHS-compliant PCBs for our customers, Singo follows best practices like a design for assembly so that the assembly process goes as smoothly as possible. We use the latest machines for assembly and automated testing to provide our customers with the highest-reliability PCBs. If you want to customize the PCB board or want to assemble PCB, welcome to contact us.

Singo is a professional custom PCB board manufacturer. Our company specializes in electronic PCB assembly. Since 2006, mainly engaged in PCB assembly and OEM/ODM electronic manufacturing services. These products include home appliances, digital products, industrial controls and medical equipment. After years of hard work, we have established long-term cooperative relationships with some internationally renowned companies.