At first glance, PCBs may seem similar in appearance regardless of their internal quality. It is by looking beyond the surface that we uncover the differences, which are crucial to the durability and functionality of the PCB throughout its lifespan.
Both during the manufacturing and assembly process and in actual use, it is vital that PCBs exhibit reliable performance. Besides the associated costs, defects during assembly may be carried over to the final product, leading to potential failures and claims in actual use. Therefore, from this perspective, it is not an exaggeration to say that the cost of a high-quality PCB is negligible.
In all market segments, especially those producing products for critical applications, the consequences of such failures can be catastrophic.
These aspects should be kept in mind when comparing PCB prices. Although reliable, guaranteed, and long-lasting products may have higher initial costs, they are worth the investment in the long run.
14 Most Important Characteristics of High-Reliability PCBs
- 25-micron hole wall copper thickness
Benefit: Enhances reliability, including improved resistance to z-axis expansion.
Risk of not doing so:
Blowouts or outgassing, electrical connectivity issues during assembly (inner layer separation, hole wall fracture), or potential failure under load conditions in actual use. IPC Class 2 (the standard adopted by most factories) specifies 20% less copper plating.
- No soldering repairs or jumper wire repairs
Benefit: Perfect circuitry ensures reliability and safety, with no repairs and no risks.
Risk of not doing so:
Improper repairs can cause circuit board disconnections. Even if repaired “properly,” there is a risk of failure under load conditions (vibration, etc.), potentially leading to failures in actual use.
- Cleanliness requirements beyond IPC specifications
Benefit: Improved PCB cleanliness enhances reliability.
Risk of not doing so:
Residue and solder buildup on the board pose risks to the solder mask, and ionic residue can lead to corrosion of soldering surfaces and contamination risks, potentially causing reliability issues (poor solder joints/electrical failures) and ultimately increasing the probability of actual failures.
- Strict control over the service life of each type of surface treatment
Benefit: Solderability, reliability, and reduced risk of moisture ingress.
Risk of not doing so:
Due to metallurgical changes in the surface treatment of aged circuit boards, solderability issues may occur, while moisture ingress can lead to problems such as delamination, inner layer and hole wall separation (open circuits) during assembly and/or actual use.
- Use of internationally renowned substrate materials – no “local” or unknown brands
Benefit: Improved reliability and known performance.
Risk of not doing so:
Poor mechanical properties mean the circuit board may not perform as expected under assembly conditions, e.g., higher expansion properties can lead to delamination, open circuits, and warping issues. Weakened electrical properties can result in poor impedance performance.
- Copper clad laminate tolerances meeting IPC-4101 Class B/L requirements
Benefit: Strict control over dielectric layer thickness reduces deviations in expected electrical performance.
Risk of not doing so:
Electrical performance may not meet specified requirements, leading to significant variations in output/performance among components within the same batch.
- Defined solder mask materials ensuring compliance with IPC-SM-840 Class T requirements
Benefit: NCAB Group recognizes “high-quality” inks, ensuring ink safety and compliance of solder mask inks with UL standards.
Risk of not doing so:
Inferior inks can lead to adhesion, solvent resistance, and hardness issues. All these problems can cause the solder mask to detach from the circuit board, ultimately leading to copper circuit corrosion. Poor insulating properties can cause shorts due to unintended electrical connectivity/arcs.
- Defined tolerances for outline, holes, and other mechanical characteristics
Benefit: Strict control over tolerances improves dimensional quality of the product – improved fit, outline, and functionality.
Risk of not doing so:
Issues during assembly, such as alignment/fit (press-fit pin issues may only be discovered upon assembly completion). Additionally, due to increased dimensional deviations, there may be issues with fitting into the base.
- NCAB specifies solder mask thickness, despite no relevant IPC provision
Benefit: Improved electrical insulation properties, reduced risk of peeling or loss of adhesion, and enhanced resistance to mechanical impact – wherever it occurs!
Risk of not doing so:
Thin solder masks can lead to adhesion, solvent resistance, and hardness issues. All these problems can cause the solder mask to detach from the circuit board, ultimately leading to copper circuit corrosion. Poor insulating properties due to thin solder masks can cause shorts due to unintended conductivity/arcs.
- Defined appearance and repair requirements, despite no IPC provisions
Benefit: Care and meticulousness during the manufacturing process ensure safety.
Risk of not doing so:
Multiple scratches, small damages, repairs, and patches – the circuit board may function but is not visually appealing. Besides the visible issues on the surface, what are the unseen risks, the impact on assembly, and the risks in actual use?
- Requirements for plug hole depth
Benefit: High-quality plugging will reduce the risk of failure during the assembly process.
Risk of not doing so:
Chemical residue from the immersion gold process may remain in incompletely plugged holes, causing solderability issues. Additionally, solder balls may be trapped in the holes, which could splash out during assembly or actual use, causing shorts.
- Peters SD2955 specifies the brand and model of peelable blue tape
Benefit: Specifying peelable blue tape avoids the use of “local” or inexpensive brands.
Risk of not doing so:
Inferior or cheap peelable tape may bubble, melt, crack, or harden like concrete during the assembly process, making it impossible to peel off/ineffective.
- NCAB executes specific approval and order placement procedures for each purchase order
Benefit: Executing this procedure ensures that all specifications have been confirmed.
Risk of not doing so:
If product specifications are not carefully confirmed, deviations caused by this may not be discovered until the assembly or final product stage, which is too late.
- Rejection of panel sets with scrap units
Benefit: Not adopting partial assembly helps customers improve efficiency.
Risk of not doing so:
Panel sets with defective units require special assembly procedures. If scrap units (x-outs) are not clearly marked or isolated from the panel set, there is a risk of assembling this known defective board, wasting parts and time.