Issue link: https://iconnect007.uberflip.com/i/1540184
52 DESIGN007 MAGAZINE I OCTOBER 2025 nificantly wider conductor than the signal-carrying conductors. If the circuit board designer relies solely on wider circuit traces for power and ground distribution, the different ground connection locations typical of those shown in Figure 1 may cause unequal resis- tance values and localized voltage drops that can compromise signal integrity. Before beginning the PCB design, the designer must establish the key operating conditions of the end product. For example, they need to understand the relationship between the thickness of the cop- per foil and the finished con- ductor width to comply with the expected current-car- rying requirement. During the hole electro-plating pro- cess, an additional copper thickness forms onto the base-copper foil surface. Table 1 defines the base- copper foil thickness varia- tions and the minimum post- plating process conductor thickness for IPC-Class 1, 2, and 3 circuit boards. IPC-2221 Class 3 circuit boards, for example, will be specified for the high-reli- ability commercial electronic products that must continuously provide the required performance without interruption. During the circuit board fab- rication process, this classification of product will undergo a higher-level inspection criterion to ensure that it will provide reliable and dependable service. Another dynamic that affects the current- carrying capability is location of the circuit. The cir- cuit conductors on the outer layer(s) of the circuit board and those laminated within the subsurface layers will have differing proficiencies. For example, the current carrying capacity of D ES I G N E RS N OT E B O O K F i g u re 1 : S u r fa c e - ro u te d p owe r a n d g ro u n d i nte r fa c e. ▼ Ta b l e 1 : E x te r n a l c o n d u cto r t h i c k n e s s re q u i re d fo r I P C C l a s s 1 , 2 , a n d 3 c i rc u i t b o a rd s (µ m ) ( S o u rc e : I P C -2 2 2 1 )