Tom Hausherr's Blog

PCB Design Perfection Starts in the CAD Library – Part 19

PCB Breakaway Panels As PCB part placements get denser, it’s necessary to add breakaway panels that add additional board material (edge rails) to accommodate the assembly process. Two parallel edges are required for a PCB to be processed in the SMT line. This is to prevent skewing through the conveyor system. Also, all odd shaped [...]

PCB Design Perfection Starts in the CAD Library – Part 18

Periphery Solder Joint Goals When it comes to solder joint goals, we are familiar with the terms Toe, Heel and Side solder joint fillets, but IPC introduced the Periphery solder joint in the latest release of the IPC-7351B. Due to the indoctrination of several new component families like Dual Flat No-lead (DFN), Land Grid Array [...]

PCB Design Perfection Starts in the CAD Library – Part 17

IPC introduced a new padstack naming convention in the IPC-7351B standard publication and it is used exclusively in the Mentor Graphics LP calculator. This article explains the breakdown of the new standard and its benefits. The padstack consists of combinations of letters and numbers that represent shape, or dimensions of lands on different layers of [...]

PCB Design Perfection Starts in the CAD Library – Part 16

Drafting elements in a CAD library part are not “Standardized” for specific values or sizes but there are recommendations that are coming out in the IPC-2610 series that include schematics, PCB assembly and fabrication. Documentation includes component outline and polarity markings for silkscreen and assembly. This article focuses on silkscreen and assembly Reference Designators. Every [...]

PCB Design Perfection Starts in the CAD Library – Part 15 QFN

The Quad Flat No-lead (QFN) component family, as seen in Figure 1, is one of the newest electronic packages to be introduced into PCB design. The QFN has pins on 4 edges of the bottom surface of the package. The QFN can have either a square or rectangle body as well as symmetric or asymmetric [...]

Inch to Metric Conversion Tables for PCB design

Here are some tips about Metric Speak that all PCB designers need to know. “Metric” is not a unit of measure. Metric is a term that describes a measurement system. You use either millimeters or microns for your PCB design units. The proper terminology to describe your working units when using the metric measurement system [...]

Do you use Imperial or Metric units for PCB design?

If the French would have won the French & Indian War against the British (the 7 Year War from 1754 to 1763) Imperial Units or the English measurement system would not exist in society today. Even the British transitioned to the metric measurement system 46 years ago. America is the last stronghold for the Imperial [...]

PCB Design Perfection Starts in the CAD Library – Part 13

Mounting holes are on every PCB design, but there is very little documentation about this subject matter. A Google or Wikipedia search on “Mounting Holes” renders no solutions to the PCB designer. Another issue that interferes with standardization is Imperial Unit ASNI hardware and ISO Metric hardware. So we’re going to have to explain both [...]

PCB Design Perfection Starts in the CAD Library – Part 12

The 3-Tier PCB library concept was originally created by IEC (International Electromechanical Commission) in 1999 and introduced to IPC in 2000. The concept had to be created as a solution for high density packaging for hand held devices to ruggedized military applications and everything in-between. The IPC-7351 and the IEC 61188-5-1 SMT land pattern standards [...]

PCB Design Perfection Starts in the CAD Library – Part 11

0.5 mm Pitch BGA Routing Solution There is a reasonable solution for via fanout and a routing solution for the 0.5 mm pitch BGA but we need to think outside the box. The board thickness is an important factor because it affects the hole plating aspect ratio. If you use a 1 mm PCB thickness [...]