Tuesday, December 20, 2016

Zero Ohm High Current SMT Jumpers

zero ohm high current SMT jumpers:

From Keystone

















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Tuesday, December 13, 2016

Capacitor Design Data, and Decoupling Placement, How-To

Capacitor Design Data, and Decoupling Placement, How-To:

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High-speed PCB Primer for SATA, PCIe, USB 2.0 and HDMI - YouTube

High-speed PCB Primer for SATA, PCIe, USB 2.0 and HDMI - YouTube:

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Friday, September 9, 2016

When does the 0402 Footprint become a 0503 ?

Let's look at these larger than typical 0402 size parts on an 0402 footprint.












Not a pretty sight, designers beware !

When does the 0402 Footprint become a 0503 ?

The answer depends on which supplier datasheet you are looking at and the specified capacitance.

Back in the day when the 0402 was really a 0402 size part you could design a nominal 0402 footprint and use it for all of your 0402 size parts, that's no longer the case.

Suppliers have been competing for years to provide higher capacitance values and increase working voltages in small form factors such as the 0402 (1005 metric) package.

To get more capacitance in the 0402 package suppliers have expanded the 0402 package tolerances to the point that the parts are now about 0503, vice 0402 sizes.

Conversions:

1.2mm ~ 47.2mil  
0.7mm ~ 27.5mil

Let's look at some 10uF 0402 Caps:

click on images to view

Taiyo Yuden - P/N AMK105CBJ106MV-F 


Kemet - P/N C0402C106M7PAC7867






















Murata - P/N GRM155R60G106ME44D  L=1.2 W=0.7 Max









TDK - P/N C1005X5R0G106M050BB  L=1.2 W=0.7 Max




















As shown in the datasheets above these 0402 10uF caps have larger than typical 0402 LxW tolerances.

Examples of typical 0402 package tolerances.

Samsung MLCC Series  Typical 0402 Cap L=1.0mm +/-0.05, W= 0.5mm +/- 0.05.
























PCB Design Guidelines from a Top Tier Contract Manufacturer.

Suggested Nominal footprints for an 0402 L=1.4mm, W=0.51mm
















Tip: These larger than 0402 size 0402 capacitor packages are usually found when the capacitance is greater than ~ 2.2uF.

In my opinion suppliers should NOT be promoting 1.2mm x 0.7mm (47x27 mil) size parts as 0402s, they should have created a new package class called 0503.

That's It !

Friday, July 15, 2016

Tenting Via In Pad - Yes or No?

"Should the thermal vias on the bottom terminated components be tented on both sides to prevent flux trapping and solder wicking or is it sufficient to tent on the top side only, or should the vias just be plugged? The Assembly Brothers, Jim Hall and Phil Zarrow, address this question."

 Link to Board Talk


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Tuesday, July 5, 2016

Why NOT use Silkscreen

Using silkscreen can cause problems.






Source: ~ Nine Dots Connect - YouTube 42 minutes. 
Introduction to DFM (Layout Considerations Part 1) - YouTube

That's It !

Wednesday, May 4, 2016

Power Plane Resonance

Power Plane Resonance: Dr. Howard Johnson 1998

A bit dated (1998) but still relevant.

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Analyzing Power Integrity Issues from Power Plane Interactions

"When a printed circuit board (PCB) includes a power plane that is near to signal traces or other power planes, there is a significant risk of energy transfer between parts of the system. Not only does this coupling lead to power switching noise being transferred into data signals, it also means that power supply systems may demonstrate additional resonances that are not seen in the individual components. This can affect the power integrity of the PCB and may reduce its speed or reliability. This paper will explore some of the potential power integrity issues that can affect a PCB and explain how simulation can be used to help reduce these effects."

Source: Analyzing Power Integrity Issues from Power Plane Interactions - White Paper

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92ML™ StaCool Materials

92ML™ Materials: Rogers

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Wednesday, April 27, 2016

NanoClear Stencil Coating | Electronic Stencil Treatment - Aculon

NanoClear Stencil Coating | Electronic Stencil Treatment - Aculon:


NanoClear Stencil Treatment


Aculon, an award-winning & proven supplier to the stencil industry, introduces Aculon NanoClear®, the best-in-class stencil treatment technology that improves print quality, increases efficiency, lowers total costs and enhances printing with small apertures. 









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Friday, April 1, 2016

PCB Libraries Footprints - SOICs Leads

When using PCB Libraries you can easily customize your PCB Footprints.

SOIC  example:

It is not uncommon for IPC 7351 default SOICs footprints to have pads that extend under the body of the gull wing ICs as shown below,
















My contract manufacturer and SMT line expert prefers SOIC footprints with pads that do NOT extend under the body of  parts, as shown below.
















PCB Libraries allows users to customize and save preferences for generating footprints. One of the settings under User Preferences > Rules is 'Minimum Trim Standoff Height'.

Out of the box the default 'Minimum Trim Standoff Height' is 0.00.  I changed this setting to 0.30 to achieve the results shown above for SOICs.























I use PCB Libraries Expert IPC-7351 footprint generator to make my PCB footprints.

That's It !

No Clean Flux Problems

Tacky Substance Under Zero Clearance Parts

"We are having failures with large, flush sitting components. When we remove the parts we find a tacky substance. Is this residue common?"


Source: Circuit Net


How To Select a Capacitor - Octopart Blog

How To Select a Capacitor - Octopart Blog

"How To Select a Capacitor BY SANKET GUPTA · MARCH 23, 2016"

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Monday, March 28, 2016

Video Analysis of Solder Paste Release from Stencil Printing


Video Analysis of Solder Paste Release from Stencil Printing

"Solder paste release from the stencil is a critical factor in print quality, and ultimately, overall electronic product quality and reliability. To better understand release mechanics, an experiment was devised using a video microscope to capture the separation of the stencil from the PCB.

The experiment incorporates different aperture area ratios, solder pastes, stencil nanocoatings and underwipe solvents to visualize their effects on paste release. This study builds on previous research that developed the test setup and recording methods, and incorporates some modifications to the original experimental configuration to improve image quality.

The outputs of the experiments are videos that demonstrate the effects of solder paste formulation, solvent under wiping and nanocoating on paste release at different area ratios. The paper will discuss the observations from the videos, and the presentation will play the videos."
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Wednesday, March 16, 2016

DDR3 Design Requirements for KeyStone Devices

"This document provides implementation instructions for the DDR3 interface incorporated in the Texas Instruments (TI) KeyStone series of DSP devices. The DDR3 interface supports 1600 MT/s and lower memory speeds in a variety of topologies (see the specific device Data Manual for supported speeds). This document assumes the user has a familiarization with DRAM implementation concepts and constraints."

Source: DDR3 Design Requirements for KeyStone Devices (Rev. B)


Definition of: MT/sec

MT/sec
(MegaTransfers per SECond) A measurement of bus and channel speed in millions of "effective" cycles per second. Also written as "MT/s," it is a rating of the actual, delivered speed rather than the frequency of the clock. For example, if timing is derived from both the rising and falling edges of the cycle rather than one complete cycle, a 400 MHz clock yields 800 MT/sec.

Sunday, March 13, 2016

DDR3 - Cycle Time

Clock Cycle time is the reciprocal of the base clock frequency.

DDR3-1066 = 266MHz base clock, or 3.75ns per cycle.
DDR3-1333 = 333MHz base clock, or 3.00ns per cycle.
DDR3-1600 = 400MHz base clock, or 2.50ns per cycle.
DDR3-2000 = 500MHz base clock, or 2.00ns per cycle


example: 1/266E10^6


















equals 3.75nS


















Friday, March 4, 2016

DDR3 Point-to-Point Design - Micron

TN-41-13: DDR3 Point-to-Point Design Support - Micron

DDR3 is an evolutionary transition from DDR2.


TN-52-02: LPDDR2/LPDDR3 Point-to-Point System - Micron

This technical note discusses guidelines to enhanced signal integrity (SI) and reduced noise for LPDDR2 and LPDDR3 devices in unterminated point-to-point and point-to-multipoint multilayer board designs.

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