Wednesday December 13 , 2017

PCB Software

Free PCB         FREE

Free under GNU license, open source and easy PCB editor. It doesn’t have any internal auto router. Supports boards up to 150cm X 150cm, also works for multilayer PCB designs for up to 16 multi-layers.

Download Free PCB | Latest Update

 

ExpressPCB        FREE + Paid Services

Professional software serves both beginners and experts. It has too many features and the software is completely free, in addition you can submit your PCB layout online then make an order to get fully made PCBs at low prices.

Download ExpressPCB for XP, 2000, NT | Download ExpressPCB for Vista and windows 7

 

PCB123 V.4.0.3        FREE + Paid Services

Reliable and user friendly software, version v.4.0.3 came with new features like datasheets real-time search, more than 500,000 new parts added and enhanced PCB schematic editor.  PCB123 is widely used by large companies with a good customer support services. Create your quick turn PCBs at the most affordable prices.

Download PCB123 |PCB123 Manuals | PCB123 Tutorials

 

4PCB  PCB Artist       FREE + Paid Services

Reliable and efficient PCB software, it has too many important features such as Netlist Import tools, multi-page Schematics, automatic component rename and auto routing. Doesn’t support MAC OS, only Windows 98, XP, Vista and 7.

Download 4PCB Artist | Video Tutorial 1 2 3 4 | Specialized Services

 

DIPTRACE        FREE + Paid Services

Professional and easy to use PCB layout software, it has all the needed features for making perfect PCBs. Software also came with built in libraries and more than 100,000 parts included. The free version can support up to 300 pins limit.

Download DIPTRACE-30 days full version trial | Download DIPTRACE-Free version | MAC Version

 

Target3001 Discover        FREE + Paid Services

The free version can support only two copper layers, 250 Pins/Pad and 120cm X 120cm boards. It has also many features and tools. Auto routing and rapid prototyping tools included. Prices Overview

Download Target3001 Discover | TARGET 3001 Newsletter

 

CadSoft Eagle PCB Software        FREE + Paid Services

Powerful PCB design solution, it has many capabilities you can use as capturing schematics, auto routing, 3D-simulation, and board layout creation.

Download Eagle Windows | Linux | MAC

 

MultiLayer PCB Overview - PcbSchematics.com

Multilayer PCBs are printed circuit boards with more than one conductor layer mostly dedicated to power connections; power planes, these layers buried inside the PCB by a way that makes each conductor layer on the outside surface. These layers; Inner layers & the top layer, are connected to each other by plating through holes and vias; the inner holes connecting the inner layers. The number of layers needed for any printed circuit board depends on the desired application and vary from one application to another, these layers can be from 3 up to 50 or more in very complicated applications. Lamination for these layers is made by some composite fibers pre-impregnated with a resin system; this resin system must be accurately chosen to meet the needed requirements such as the resistance to chemicals, maintaining the dielectric constant and Bearing the expected temperature. Multilayer PCBs able to carry high speed devices, large complicated schematics and all applications required controlling the impedance.

 

The Processes of multilayer PCB manufacturing is divided into two parts: the outer layer PCB and the inner layers PCBs. The inner layers of any product usually seem to be typically standard and the manufacturing processes of these layers always contain several common steps such as:

  • Layer cleaning either mechanical or chemical cleaning
  • Photo-resist materials coating and photo-resist exposure
  • Etching the exposed copper
  • Stripping the remaining photo-resist
  • Lamination by oxide layer
  • Plus too many other steps

 

The outer layer processes in manufacturing contain too many steps such as:

  • Isolating the outer layer of the inner layers with the PrePreg; pre-impregnated fibers
  • Laminating with copper foil to create the copper surface of the outer layer
  • Drilling of the holes and vias between the outer layer and the inner layer
  • Copper plating in the holes and vias to maintain conductivity between layers
  • Coating the outer layer with a photo-resist material, and exposing
  • Stripping of the remaining photo-resist and etching useless remaining exposed copper
  • Solder masking, silk screening, gold plating, additional holes, mechanical components considerations and finalizing related steps
  • Plus too many other steps

 

What are Backplanes?

Backplanes in the printed circuit boards science are special cases of multilayer PCBs.

Contain large quantities of connectors that have been installed using press fit pins.

Used also to distribute large amounts of dc power to the circuit, this is accomplished by laminating the power planes inside backplanes and bolting bus bars onto the outside surfaces, some components need these active elements such as the surface mount ICs.

Backplanes make The Final PCB thicker than the original multilayer PCB; it makes the process of PCB manufacturing very hard as the press fit pins have to deal with the added thickness.

 

Six-layers or more PCBs usually built on the standard (18 in * 24 in) panels using the lamination technique mentioned above, also the four-layers PCBs laminated using a technique called mass lamination with a panel of (36 in * 48 in); i.e., 4*standard panel. The pricing of Multilayer PCBs are affected by several factors:

 

  • How many PCBs Can be Fitted in a standard panel using the lamination technique
  • The thickness of the inner copper layers and the outer layer
  • The accuracy of the copper layer thickness
  • The controlled impedance requirements
  • The minimum copper plating in vias
  • The diameter of traces and minimum spacing
  • The gold plating requirements
  • Testing to CAD Net-List
  • There are too many other factors that can affect the multilayer PCB pricing such as the solder mask, the silk screen and other factors depend on the client requirements

 We are now preparing a DIY; Do It Yourself tutorial for how to make a quality pcb at home with very simple tools? and how to print the complicated pcb schematics without loosing connection, dots and lines? Come back soon!

 

multilayer pcb examle, how the layers placed to form the multilayer pcb and how holes can connect through layers

   

PCB Design Considerations

1-Time & Frequency Domain Analysis – Important facts for oscilloscope readings

 

First we have to learn more about the time domain analysis versus the frequency domain analysis and how pcb design can be affected by these parameters. Digital printed circuit board designers always measure the performance of PCB delay, rise and fall times under the meanings of the time domain. On the contrary the analog designers express delays in terms of frequency domain as most analog phenomena can be described well by the frequency domain.

 

  • f (Frequency) = 1/T
  • T(Time) =1/f
  • f(frequency) =1/(T |rise +T |fall)
  • f |knee =0.5*[1/(T |rise +T |fall)] = Knee frequency

Knee Frequency: the needed amount of time the voltage of the digital circuits can rise from 10% of a logic '0' to a logic '1' or rise from 10% of a logic '1' to a logic '0'. Also the knee frequency is related to the whole system bandwidth and the 3-db bandwidth.

 

You have to choose the right oscilloscope probe that match your circuit amplitude, load, capacitance and speed, probes are usually used to make sure that your circuit is isolated completely from the oscilloscope  so that you can get that most accurate reads, these probes are divided into voltage and current probes, voltage probes measures the voltage on the circuit and current probes measures the current, in the market you will find two types of voltage probes; passive or active , the current probes are the same as we need the active elements to amplify the weak signal for more accurate analysis, the passive voltage probe is commonly used by engineers everywhere and it named by the attenuation ratios as described below.

 

Voltage Probe

Load Added To Circuit

Capacitance Added To Circuit (in average)

Information

 

1X

 

1000 Kilo Ohm

 

100 PF

-Adds more capacitance, can affect the circuit operation negatively.

-Doesn’t attenuates the signal amplitude

 

10X

 

10000 Kilo Ohm

 

12.5 PF

-Commonly Used, Stick on the 10X voltage probe, suitable for the most circuits.

-Attenuate the signal amplitude by 10X with 500 volts maximum input.

 

100X

 

100000 Kilo Ohm

 

2 PF

-Used in very sensitive circuits.

-Attenuate the signal amplitude by 100X with 500 volts maximum input

 

High Volt.

 

Higher

 

Lower

-Attenuate the signal amplitude by more than 100X with maximum voltage input starting from 1KV.

 

 

Make sure that you are using a probe bandwidth that is the same as your scope or little faster.

 

2-Custom PCB Characteristics

 

Before starting the implementation of the electronic circuit and drawing on the printed circuit board, we need to set some parameters and constants:

 

Trace Width| minimum = from 0.1 mm to 0.25 mm

Copper Layer Thickness = from 0.2 mm to 0.1 mm

Material Dielectric Constant| typical = FR-4 PCB Sheets = er = 4.5

The Dieletric Constant for FR4 equals 4.5 in its inner layer is considered to work for frequencies up to ( 2GHz). You should decrease this value to be 4.2 if you work with high frequencies (up to 10GHz).

Material Tangent Constant = for FR4 is approximately 0.015

The Tangent Constant of the FR-4 PCB sheets makes it hard to design microwave circuits on it, as short distances can make undesirable loss. Microwave seekers should use the high speed sheets instead of FR-4, but FR-4 PCB sheets still able to cover these frequencies with some troubles.

 

 

3-Very Important Parameters

 

Any electronic circuit has many features we should consider before designing the printed circuit board, input and output resistances of the circuit is a very important parameter, also the inductance and the capacitance of the circuit can be affected by the size, diameter and thickness of  PCB holes and the transmission lines, that’s means you have to consider well the diameter of the holes, the spacing between holes and the spacing between copper lines. In microwave circuits these parameter is very important as the resonance frequency affected by the increase of inductance and capacitance of the circuit, also the resistance seen by antennas can be changed due to added resistance made by the copper in the printed circuit board and also the resistances added by other elements in the circuit; capacitors, coils, transformers and so on.

 

For example, the typical narrow trace in the printed circuit board can add up to 0.8 PF capacitance for every 1 CM in the printed circuit board, also the ceramic capacitors which are usually named the decoupling capacitors add more resistivity to the circuit that’s why some times we use several parallel capacitors to decrease the series resistance occurred. Also the wires in the printed circuit board which are longer than 2.5 Cm have an inductance of 80 to 90 nH, this change in the inductance can be a disaster in microwave designs.

 

4- Be Aware of Transmission Lines

 

The length of the line is the point of interest, for the typical transition time of 2nS each line has a length more than 10 Cm can be considered as a transmission line, also for fast transition of 1nS transmission lines calculations can be applied for every 5 Cm lines. 

 

5- Inductive and Capacitive Crosstalk

 

Inductive & capacitive crosstalk can occur in parallel lines which are very close to each other; especially in data buses, so try to eliminate any obstacles in the ground plane to minimize the effect of crosstalk.

Also you should always find the shortest path from VCC to GND to avoid too many problems.