A double-sided board carries copper on both faces and joins the two layers with plated through-holes. It is still the workhorse of the assembly industry: the layer count keeps the price down, the second copper layer frees the routing, and the design rules are the same ones a 38-layer board is held to, because both come off the same line.
What the second layer buys
- Routing room — a two-layer board can cross conductors instead of routing around them, so a dense control section fits without adding layers.
- Ground and power planes — the second face carries a solid plane, which shortens the return path and removes the loop area that a single-sided layout leaves open.
- Component density — parts can be placed on both sides, which halves the outline where the enclosure is the constraint.
- Cost — two layers avoid the lamination cycles of a multilayer build while keeping impedance controlled to ±10 % where the stack-up needs it.
Materials and panel sizes
FR-4 is the standard core, with high-Tg FR-4 for higher soldering temperatures, CEM1 and FR-1 for cost-driven consumer work and halogen-free laminate where the customer's own approvals ask for it. Panels run up to 580 × 1900 mm and 0.1–6.0 mm thick, with copper from 0.5 oz to 20 oz on the outer layers — a 20 oz two-layer board is a common way to carry a heavy current without going to a heavy-copper stack-up.
Process and inspection
Boards are drilled mechanically from 0.15 mm or by laser to 0.1 mm, plated, imaged at 0.075 mm line and space, then finished in HASL, lead-free HASL, ENIG, immersion silver or tin, flash gold, golden finger, OSP or carbon ink. Outline is held to ±0.10 mm and bow and twist to 0.7 %; every panel is electrically tested before shipment, and boards are fabricated to IPC-6012B and IPC-A-600H with UL recognition under file E354070.
Where two-layer boards are used
Industrial control and relay logic, power supplies, LED lighting and drivers, consumer electronics, instrumentation and telecommunications equipment. Double-sided reflow allows both faces to be populated, which keeps the outline small in wearable and handheld products; where the design needs microvias rather than through-holes, the same panel can be built as an HDI board.
Getting a quotation
Send the Gerber set with the layer count, copper weight, surface finish, panel size and quantity. Prototypes come back in 1–3 days and medium volume in 4–10 days, with stencils cut within four hours; the capability page holds the process limits used for the quotation and the certifications page the issued certificates.
When the double-sided boards move into assembly, the China PCB assembly page covers SMT, through-hole, component sourcing and box build from one plant.
