Teardrops and Trace Entry Design What a Teardrop Is A teardrop is a small taper of copper that blends the trace into the pad, so that the junction is a smooth transition rather than a right angle. The taper adds copper at the point where the trace meets the pad,…

Annular Ring and Pad Design Rules What the Annular Ring Is The annular ring is the width of copper that surrounds a drilled hole on the pad. It is what remains after the hole has been drilled through the pad, and it has to absorb the drilling’s position tolerance, the…

SMT Reflow Solder Joint Tear Test: Pulling the Joint Apart Buyers and engineers often focus on the finished product and forget the production line behind it. In practice, most field failures can be traced back to process decisions made during assembly. Understanding SMT reflow solder joint tear test gives you…

Thermal Relief Design for Soldering Why a Plane Makes Soldering Harder A copper plane conducts heat better than the laminate, so a pad that is connected directly to a plane draws heat away from the joint during soldering. The result is a joint that reaches a lower peak temperature, that…

Board Level Shielding and RF Cans When a Shield Is Needed A board level shield, often called a can, is a metal cover over a section of the circuit that confines the field of an emitter or protects a sensitive receiver. It is used when the layout, the filtering and…

PCB Laminate Coefficient of Thermal Expansion: How Much the Board Grows Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at PCB laminate coefficient of thermal expansion from the perspective…

Microvia Reliability in HDI Boards What a Microvia Is A microvia is a small laser drilled via, usually with a diameter below about a tenth of a millimetre, that connects an outer layer to the layer immediately beneath it. It is the element that makes a high density interconnect possible,…

Blind and Buried Vias in Multilayer Boards What the Two Terms Mean A blind via starts at an outer layer and ends at an inner layer, so it is visible from one side only. A buried via connects two inner layers and is not visible from either surface. Both exist…

PCB Solder Mask Inkjet Printing: Drawing the Mask Directly Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This article…

Backdrilling and Stub Removal The Stub Problem A plated through hole connects every layer it passes through, so a via that is used to connect an inner layer still has a length of barrel below the connection. That unused length is a stub, and at high frequency it behaves as…