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Overlooked features of stencil printers: why operators skip important features–and what to do about it

Automated vision inspection is among the top features of most advanced stencil printers. Other top features and process-related techniques include underside cleaning with vacuum, automatic placement of support pins and auto paste dispensing. In some PCB assembly camps, vision inspection and other major stencil printer features, as well as setup process techniques, are not used. […]

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‘Checking up’ on medical electronics: a healthy relationship involves understanding FDA documentation

Medical electronics assembly demands a different set of criteria than do commercial PCBs. In particular, the US Food and Drug Administration (FDA) requires specific documentation, especially for verification of certain processes. Complying with FDA-approved documentation is considerably easier when an EMS provider is ISO 13485 certified. The reason: the considerable traceability embedded in the standard. […]

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Auditing a fabricator: guidelines for prototypes and production boards overlap, but for offshore production the rule is caveat emptor

PWB procurement can be categorized as either procuring prototype or production boards or both. But the common denominator is both require assurances the fabricator has the capability and capacity to deliver the required quantities on time and with high quality. A PWB order ranging from a few units to a few thousand can be placed […]

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Eliminating board defects: the assembly drawing should specify process-related issues

The processes involved in eliminating board defects cut a wide swath through design, fabrication, and even assembly. Along the way, experience and know-how play pivotal roles because solutions to many defect-prone PCB areas are not covered in textbooks. PCB defects run the gamut, for example, from deteriorated RF signals resulting from inappropriate shielding to incorrectly […]

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Creating Ideal Solder Joints: effects of stencils and thermal profile are reviewed

Stencil quality and the major elements comprising it play a pivotal role in ensuring solder paste is properly deposited on a PCB’s surface mount pads. Experience in defining and cutting perfect stencils is critical because there are virtually no textbook solutions on how best to make stencils. When properly combined, stencil quality and other associated […]

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Taking Stock of Component Procurement: proper purchasing procedures prevent post-assembly pitfalls

Component procurement runs the gamut of potential issues and pitfalls, especially with procurement processes and policies mingled with rapidly emerging component technologies and end-of-component-life requirements. Several major areas must be carefully considered to maintain efficient purchasing. They include tracking date codes; evaluating inventory levels at in-house and reseller levels; maintaining checks and balances; watching for […]

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Placement machine tolerances and limitations: DfA is the best solution for grappling with varying machine tolerances

When it comes to effective component placement, machine tolerances, height restrictions and fixture limitations require close attention because they pose assembly issues and hinder process flow. Equipment involved here includes pick-and-place machines, flying probe and ICT testers, wave solder machines, reflow ovens, AOI and other associated gear. Each piece of equipment is designed with different […]

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A Primer on AOI and AOT: capabilities vary, but programming time is the general differentiator

Inspection is not the same as electrical testing. Rather, it is performed via optical means during PCB assembly and directed at ferreting out defects. Integrated with assembly equipment, automatic optical inspection (AOI) and automatic optical test (AOT) are at the epicenter of these test and inspection methods. A competent T & I technical team with […]

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Pb-free rework differences and practices: no lead means using four heating zones and one cooling zone for reflow

Good assembly practice calls for retrained staff and new profiles. Maintaining high quality rework is more challenging because the PCB and components adjacent to the targeted rework component are subjected to multiple cycles of higher temperatures. To maintain the integrity of the PCB laminate, the maximum preheat temperature is set approximately 10[degrees]C below the Tg […]

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