Issue link: https://iconnect007.uberflip.com/i/1537475
44 DESIGN007 MAGAZINE I JULY 2025 end product. For example, understand the rela- tionship between the thickness of the copper foil and the finished conductor width that will be nec- essary to comply with the expected current-car- rying requirement. The operating temperature of the product can also affect the effi- ciency of the copper conductor's current-carrying capability. The dielectric base material is supplied with copper foil pre-lam- inated onto one or both sides, but copper foil materials can be spec- ified in sheet form for sequential lamination with a variety of optional surface topographies. The general- use foil has a rather rough surface on one side, ensuring a reliable bond between the copper and resin layer of the laminate material. External layer copper foils, for example, will begin with a thick- ness equal to the foil thickness on internal layers. During the electro- plating process, an additional cop- per thickness is formed onto the base-copper foil surface. Base cop- per foil thickness variations and the minimum post-plating process con- ductor thickness for IPC Class 1, 2, and 3 circuit boards are defined in Table 3. Another factor that affects the current-carrying capability is location of the circuit. The circuit conductors on the outer layer(s) of the circuit board and those laminated within the subsurface layers will have dif- fering proficiencies. For example, the current-carrying capacity of the external layer conductor may require 2X the thickness of that defined for the internal layer conductor. Note: For greater detail in deter- mining the current-carrying capac- ity for printed circuit conduc- tors, refer to IPC-2152. This docu- ment sets the industry standard for defining the appropriate sizes for both internal and external conductors as a function of the cur- rent-carrying capacity required as well as calcu- lating the finished copper conductor's tempera- ture rise potential. D ES I G N E RS N OT E B O O K Ta b l e 3 : Est i m at i n g c u r re nt - c a r r y i n g c a p a c i t y of c o p p e r fo i l s Ta b l e 2 : Ty p i c a l P C B p r i c e c o nt r i b u to r s Source: RUSH PCB Inc. 1 Source: RUSH PCB Inc.