Connector Footprint Design Guide A connector footprint is the set of pads, holes and keep out areas that a connector needs. It is copied from a datasheet, drawn from a drawing or taken from a library, and the differences between those three sources cause more assembly problems than any other…

Mixed Alloy Reflow Profile For Backward Compatibility Not every assembly uses one solder alloy. A board may carry a lead free ball grid array and be soldered with a tin lead paste, or it may carry a leaded component on a lead free board, or it may be assembled with…

Solder Mask Thickness: Preparation, Placement and Process Control Solder mask thickness is a number that rarely appears on a drawing and that decides several things at once. The film has to insulate the copper, survive the soldering process, hold its shape between fine pads and adhere to the laminate. A…

Through Hole Solder Barrel Fill And Wicking A through hole joint is judged by two things that are visible and one that is not. The visible ones are the fillet on the solder side and the fillet on the component side; the invisible one is how much of the barrel…

Conformal Coating Process Guide A conformal coating is a thin polymer film that is applied over a populated board to keep moisture, dust and chemicals away from the circuits. The film is a few tens of microns thick, it follows the shape of every component, and it is the last…

ESD Protection Placement And Routing Rules Electrostatic discharge protection is designed as a circuit and then destroyed by its layout. A protection device that is placed a centimetre from the connector it is meant to defend will allow the transient to travel through the board, couple into neighbouring traces and…

Depanelization: Design Rules and Process Limits Depanelization is the step where the finished panel becomes individual boards. It happens after all the assembly work, which means the components, the solder joints and the board itself are all exposed to the separation force. A method that is chosen for speed can…

Desiccant and Moisture Barrier Packaging for PCB Storage Bare boards and moisture sensitive components absorb water from the air, and that water turns to steam when the part is heated. The result is delamination, blisters, cracked packages and, in the worst cases, a board that fails during reflow. Moisture barrier…

Component Courtyard And Clearance Design Rules The land pattern defines where the solder joints are; the courtyard defines the space the part needs around them. It is the outline of the body plus the room the placement nozzle, the rework tool and the inspection equipment need to reach the part…

PCB Fabrication Lead Time and Schedule Planning Fabrication lead time is a design variable that most projects discover too late. A stack up that requires a specialty laminate, a finish that only two shops can apply or an aspect ratio at the edge of capability all add weeks, and those…