Stencil Life and Replacement Criteria in SMT Printing A stencil looks permanent, but it wears every time a squeegee crosses it. Tension falls, apertures deform, the foil surface roughens and the edge where paste releases starts to hold material instead. None of this happens quickly, which is why stencil life…

Panelisation Design and Depaneling Method Choice for SMT Panelisation is the practice of building several copies of a board in one panel so that the assembly line has something large enough to handle, and the way that panel is designed decides how the boards behave when they are finally separated.…

Difficult Board Prototypes: Layout and System Test Some boards are difficult for reasons that have nothing to do with the circuit diagram. Fine pitch devices, controlled impedance, mixed analogue and digital sections and tight mechanical constraints all push the design outside what a generic layout can support. Building one successfully…

Flexible Circuit Assembly: What Changes On A Flex Board Assembling components onto a flexible circuit is not the same job as assembling them onto a rigid board, even though the equipment and the solder are the same. The substrate bends, absorbs moisture, changes size during processing and cannot support the…

Sequential Lamination HDI Stackup Design In a conventional multilayer board every via passes through the whole stack. As density rises, those through vias consume space on every layer they cross, and the space they take becomes the limiting factor in the layout. Sequential lamination solves the problem by building the…

Measuring Flatness and Coplanarity on Flexible Circuits The flatness of a flexible circuit matters at the interfaces where it has to make contact. A flex tail that plugs into a connector must be flat so that all of its contacts touch their counterparts, a flex that is bonded to a…

PCB Non Disclosure for Gerber: Protecting the Design 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 non disclosure for Gerber from the perspective of a PCBA factory…

Solder Paste Printing Defects And How To Clear Them Solder paste printing is the step that decides how much of the rest of the assembly process will go smoothly. The stencil deposits paste on every pad at once, and if the deposit is wrong on one pad, no amount of…

Embedded Resistor and Buried Component Design An embedded resistor is formed from a resistive layer inside the board rather than from a component placed on the surface. The technique removes parts from the surface, shortens the connection to the layer it terminates, and improves the behaviour of high speed nets…

FPC Design Parameters For Appliance Electronics An appliance is a difficult environment for an interconnect. The inside of a washing machine, a refrigerator or a kitchen appliance is a three dimensional space occupied by motors, heaters, sensors and a control board, and the connections have to run between them without…