Purpose - Put some theoretical background to Mill a circuit board using Modela
Based on various needs we come across, many of us wish to build intelligent systems comprising of little or more electronics. Passive components such as Resistors, capacitors, active components such as Op Amps and intelligent components such as Microcontrollers, Signal Processors etc. are often become a party to such electronic systems, based on applications.
While this tutorial does not imply to talk about circuit designs and realted processes (in order to produce elements required to prepare the final physical board), it is worth taking a look at Packages of electronic components. At the end, an object, when is being carved out, the entity (man and/or machine) making the board should be aware of the boundaries and fineness of the object, in reference with its own limitations (may be we should start saying resolution henceforth). Simply put - the size of a cutting edge should not be larger than object to be cut.
Packages
Every electronic component has certain length and width. Apart from the behavioural characteristics, a component is selected, also, based on its size. Size of an electronic component is a function of its "package". Package is a standard keyword, when it comes to electronic components. All over the world a user and a vendor of components, would understand what one would mean by 1206 or 603 or TO220. For example a resistor can be seen in following packages
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source - http://www.eeweb.com |
A designer will have to consider what packages she/he wants to use, while realising the idea. Usually, the main factors that
drive the package selection are -
1) What packages are available locally.
2) What is the targeted size of the board
3) Which packges
satisfy the electrical parameters (such as wattage).
However, there is a 4th parameter that one will eventually need to consider,
sooner or later -
4) Who is going to do the component placement?
If the component placement is going to be done manually, it is
required that the components be large enough and still small enough to reach upto the final expected product. In my perspective,
1206 is one of the packages we can choose if manual placement is to be done. 603 is also a choice, but becomes a bit cumbersome. Going below
would make it difficult to solder manually.
In the fablab inventory 1206 is a preferred package, though not a rule. Note that 1206 is a package applicable to Resistors, nonpolarised Capacitors
, LEDs. A diode or zener diode will have different nomenclature. For example a 1.1V zener diode comes with SOD123
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Some SMD Diode Packages |
With the background above let me talk about milling of PCBs in a Fablab