Component placement decisions made during PCB layout have a direct impact on assembly yield and reliability. Poor placement choices can cause tombstoning, solder bridges, insufficient solder joints, and difficult rework. This guide covers the key SMT placement design rules that every PCB designer should know.
Minimum component spacing is determined by the placement equipment capabilities and the need for rework access. For SMT components, maintain a minimum of 0.2mm between component bodies. For components that may require rework, increase this to 0.5mm to allow access for soldering iron or hot air.
For mixed SMT and through-hole boards, maintain at least 2mm clearance between SMT components and through-hole component leads on the same side of the board.
Orient all polarized components consistently. The IPC standard recommends that pin 1 of ICs faces up or left, and that the positive terminal of capacitors and diodes faces up or right. Consistent orientation reduces placement errors and simplifies visual inspection.
For small passives (0402, 0201), orient all components in the same direction on each section of the board. This reduces the chance of tombstoning by ensuring both pads of each component enter the reflow zone simultaneously.
Avoid placing small passives adjacent to large thermal masses (power components, large copper pours). The thermal gradient during reflow can cause one pad to melt before the other, leading to tombstoning.
For high-power components, ensure adequate thermal relief in the copper pour connections. Components connected directly to large copper pours without thermal relief can be difficult to solder reliably.
Place test points on all critical nets, accessible from the bottom side of the board. Test points should be at least 1mm diameter and placed on a 2.54mm grid for ICT fixture compatibility. Avoid placing test points under components or in areas that will be covered by conformal coating.
Design for Manufacturability (DFM) analysis is the single most effective way to reduce PCBA defect rates. This checklist covers the 12 most common DFM issues our engineering team identifies during pre-production review — and how to fix them before they reach the production floor.
Understanding the different inspection methods used in PCBA manufacturing helps you specify the right quality requirements for your project. This article explains what each method detects, its limitations, and when to require each type of inspection.
Ordering small batch PCBA for the first time? This guide covers everything you need to know: what files to prepare, how to evaluate manufacturers, what questions to ask, and how to avoid the most common mistakes that delay projects and inflate costs.
