What Truly Defines a Highly Reliable PCB?

November 11, 2025

Nowadays, there are numerous PCB manufacturers, and competition is exceptionally fierce. Some suppliers, in an effort to reduce costs, take unconventional shortcuts by using other cheaper, inferior substrate materials to replace the original ones. Although PCBs produced this way may pass various tests and function normally initially, a crisis is quietly looming – the use of inferior materials significantly shortens the product's service life. Short lifespan is a manifestation of poor PCB reliability, the opposite of which is high reliability. Today, we will delve into what constitutes true high reliability. So, what exactly is "high reliability"?

Everyone knows that electronic products always have a limited service life. Therefore, some define high reliability as: under specified conditions and within a specified time, the product is allowed a small number of acceptable failures. Another common definition is: even after exceeding the initial service life, the product can still be used for a period after repair, which is also generally considered to reflect high reliability.

The Historical Origins of "High Reliability"

The concept of "reliability" was initially proposed specifically for electron tubes and was primarily led by military research. In August 1952, the U.S. Department of Defense established the famous Advisory Group on Reliability of Electronic Equipment (AGREE). In July 1957, this group issued a report recommending reliability measurement during the trial production and manufacturing of electronic equipment. Consequently, quality management and corporate management departments in many companies set up specialized units dedicated to reliability testing for their products. Later, with the development of electronic products, corporate requirements for them became increasingly stringent, especially among major brands, followed by quality-seeking small OEMs. For high reliability, the future trend is clear: pursuing higher quality while simultaneously striving to reduce costs.

As the core component of electronic products, PCBs represent the development level of the electronics industry. All electronic products should emphasize high reliability, and it is even more imperative to demand that "PCB manufacturers" fully guarantee the high reliability of their products!

Ten Characteristics of Highly Reliable PCBs

1.20μm Hole Wall Copper Thickness

Benefit: Enhances reliability, including improved resistance to Z-axis expansion.
Note: Insufficient hole wall copper thickness (<20μm) can lead to blowholes, outgassing, electrical connectivity issues during assembly (e.g., inner layer separation, hole wall fracture), or failure under load conditions in actual use. If the hole copper thickness is consistently ≥20μm and uses chemical copper deposition process instead of conductive adhesive process, the bond is stronger and conductivity is better.

2.No Solder Repairs or Open Trace Repairs

Benefit: Perfect circuits ensure reliability and safety, no repairs, no risks.
Note: Improper repairs can cause board open circuits. Even "proper" repairs carry a risk of failure under load conditions (e.g., vibration), potentially causing issues during actual use.

3.Use Internationally Renowned Substrates, Avoid Inferior No-Name Brands

Benefit: Improves reliability, service life, and consistent performance.
Note: Using inferior substrates greatly shortens product life. Their poor mechanical properties mean the board may not perform as expected under assembly conditions, e.g., higher expansion rates can lead to delamination, open circuits, and warpage; poor electrical characteristics can result in inferior impedance performance.

4.Use High-Quality Ink

Benefit: Ensures PCB print quality, improves image reproduction fidelity, and protects circuits.
Note: Inferior ink can cause adhesion, solvent resistance, and hardness issues. These problems can lead to solder mask separation from the board and ultimately copper circuit corrosion. Poor insulation properties can cause short circuits due to unintended electrical connectivity/arcing.

5.Cleanliness Requirements Exceeding IPC Standards

Benefit: Improving PCB cleanliness enhances reliability.
Note: Residue and solder paste buildup on the board pose risks to the solder mask; ionic residue can lead to solder joint corrosion and contamination risks, potentially causing reliability issues (poor solder joints/electrical failures) and increasing the probability of actual field failures.

6.Strictly Control the Shelf Life of Each Surface Finish

Benefit: Ensures solderability, reliability, and reduces the risk of moisture ingress.
Note: Aged surface finishes undergo metallurgical changes, potentially causing solderability issues. Moisture ingress can lead to delamination, inner layer and hole wall separation (open circuit) during assembly and/or actual use. For example, in HASL, a thickness ≥1.5μm offers a longer shelf life.

7.High-Quality Via Filling

Benefit: High-quality via filling reduces the risk of failures during assembly.
Note: Insufficiently filled vias can trap chemical residues from the ENIG process, leading to solderability issues. Also, solder balls can hide in the vias, which might splash out during assembly or use, causing short circuits.

8.Laminate Tolerances Comply with IPC 4101 Class B/L Requirements

Benefit: Strict control of dielectric thickness reduces deviations in electrical performance expectations.
Note: Electrical performance might not meet specifications, leading to significant variations in output/performance among components from the same batch.

9.Strict Control Over Outline, Hole, and Other Mechanical Feature Tolerances

Benefit: Strict tolerance control improves dimensional quality – enhancing fit, form, and function.
Note: Poor tolerance control causes assembly issues, such as alignment/fit problems (e.g., press-fit pin issues only discovered after assembly). Also, increased dimensional deviations cause difficulties when mounting into housings. Per high-reliability standards, typical requirements are: hole position tolerance ≤0.075mm, PTH hole diameter tolerance ±0.075mm, outline tolerance ±0.13mm.

10.Adequately Thick Solder Mask

Benefit: Improves electrical insulation, reduces the risk of peeling or loss of adhesion, and enhances resistance to mechanical impact – wherever it occurs!
Note: Thin solder mask can lead to adhesion, solvent resistance, and hardness problems. These issues can cause the solder mask to separate from the board and ultimately lead to copper circuit corrosion. Poor insulation due to thin solder mask can cause short circuits from accidental conduction/arcing. Solder mask thickness is best maintained at ≥15μm.

The above ten high-reliability characteristics represent the most fundamental PCB execution standards. From selecting premium raw materials to strictly controlling production processes, the goal is solely to manufacture high-quality boards!

Shenzhen Electronic Technology Co., LTD strictly adheres to these ten requirements to maintain PCB high-reliability characteristics. We use internationally renowned substrates, strictly control outline tolerances, and provide customers with professional and reliable custom PCB services.