Understanding PCB Baking in the PCB Assembly Process
As a professional electronic manufacturing service provider specializing in PCB assembly, we at CEN PCBA place immense importance on processes that ensure the reliability and performance of printed circuit boards (PCBs). One such critical process is PCB baking. This article delves into the intricacies of PCB baking, its necessity, and its role in delivering top-quality electronic assembly solutions.
What is PCB Baking?
PCB baking is a crucial step in the PCB assembly process designed to remove moisture from the printed circuit boards. Moisture can be a significant problem in PCBs, as it can become trapped within the board’s layers. When exposed to the high temperatures of soldering processes, this moisture can turn into steam, potentially causing delamination or other damage to the PCB.
The effectiveness of PCB baking is influenced by the composite materials used in the board. For instance, polyimide flex and rigid materials tend to absorb more moisture than FR4 panels. By baking the PCBs, we can extract this moisture, enhancing the board’s overall performance and reliability.
How Does PCB Baking Work?
The PCB baking process involves placing the boards in an oven and heating them to temperatures typically ranging from 100°C to 130°C. This heat effectively evaporates the moisture trapped within the PCB. However, it is crucial to carefully monitor the temperature and duration of the baking process to avoid overheating, which can damage the boards.
We measure the board’s weight before and after baking to confirm moisture removal. This weight change indicates the amount of moisture that has been successfully extracted.
Why Bake PCBs?
Baking PCBs serves several vital purposes, including:
- Preventing Condensation Issues: Baking stops condensation from escaping through copper-coated gaps, which can cause blowholes and pinholes.
- Reducing Outgassing: This process limits outgassing, which can impact soldering quality during both manual and machine soldering processes.
- Preventing Delamination: Baking prevents delamination or “measling,” which can occur when moisture accumulates in holes or at epoxy-composite junctions.
- Improving Solder Quality: Proper baking ensures better soldering quality by removing moisture that could cause defects during the soldering process.
Is Baking Necessary for All PCBs?
Not all PCBs require baking. The necessity depends on the board’s design and the materials used. While baking is an effective moisture removal method, implementing preventative measures during the PCB design and production phases can often mitigate the need for baking. For example, controlling the lamination process in a temperature-regulated environment can effectively dry the board without the need for additional baking.
Conditions for Effective PCB Baking
To ensure optimal results from PCB baking, specific conditions must be met, particularly when using Organic Solderability Preservative (OSP) surface finishes. Here are the recommended baking durations based on storage conditions:
- Short-term storage (up to 2 months): Bake at 120°C for one hour.
- Medium-term storage (up to 12 months): Bake at 120°C for two hours.
- Extended storage (6-12 months post-production): Bake at 120°C for four hours.
- Long-term storage (exceeding 12 months): Bake at 120°C for six hours. Note that prolonged storage may compromise PCB layers, potentially leading to reduced performance.
After baking, PCBs should be stored for no more than five days before being listed online or delivered. If delays occur, rebaking before listing is essential.
Rigid PCB Process for Different Surface Finishes
All PCBs, regardless of thickness, undergo baking for a minimum of two hours at 120°C. The duration between baking and soldering varies based on storage conditions. Specifically, at a relative humidity of 50%, the recommended maximum hold time is eight hours. However, if boards are maintained in an oven at 35°C, this hold time can extend beyond the standard duration.
Purpose of the Baking Process for Components
The primary aim of the baking process is to eliminate moisture content in specific electronic devices, particularly moisture-sensitive parts. Moisture-sensitive plastic packaging surrounding a part can absorb water, which during reflow soldering, can lead to catastrophic outcomes due to high temperatures. The trapped moisture forms water bubbles that expand, potentially damaging the part’s internal components.
Moisture sensitivity can also reduce the shelf life of components. Components with higher sensitivity levels absorb water more quickly, diminishing their longevity. By baking, we can help extend the shelf life of these components and ensure their reliability in the final product.
PCB baking is a vital process in the PCB assembly industry, playing a significant role in ensuring the performance and reliability of electronic components. By effectively removing moisture, we can prevent defects such as delamination, blowholes, and poor soldering quality, thus enhancing the overall quality of our PCBs.
At CEN PCBA, we leverage our extensive experience in PCB assembly to provide unmatched precision and quality in every board we produce. Our meticulous PCB baking process is just one example of our commitment to delivering industry-leading electronic assembly solutions.
For more information on our PCB assembly services and how we can help you achieve your electronic product goals, contact us today.
