Building circuits and PCBs

The ultimate connection

Building electronic circuits is a fascinating pastime and if not your profession many new adventurers find the world of SPICE (Simulation Program with Integrated Circuit Emphasis), building PCBs (Printed Circuit Boards) and getting a professional finish rather scary. And expensive!

Firstly, your best friend is your computer.  Many years back Joe Inventor was the amateur radio Ham.  Our biggest and best supplier of electronic components in the Western Cape was then of course Hamrads.

Studious types would wind their way through library books to find a circuit to build, usually radio or audio. The circuit used point to point wiring and had a multitude of transformers, chokes and capacitors in the power supply.  The vacuum tubes used high voltages and were either directly or indirectly heated with a low voltage supply.  The biggest problem was always faulty wiring and dry joints. We used an AVO meter.

PCB – layer side soldering

Now we use SPICE, breadboard, low current devices,  one or two 9V batteries and a DMM. The biggest problem is always faulty wiring and dry joints.

For the newbie LTSpice is the first and last word in free electronic simulation.  I have used both TINA (Texas Instruments) , EasyEDA (online) and NL5 Circuit Simulator (up to 20 components usage for free). There’s hundred of simulation packages on the market so if you don’t like the one, try another. There is one trap however. Price.  SPICE programs can run into hundreds of thousands of Rands and is therefore out of reach for personal usage.  LTSpice does have a very large user community but can be daunting for the first time user. I know,  I’ve been there.

Component placement and circuit boards is another area which can put the user through a steep learning curve.  If we are looking at just laying a circuit down on a board for printing (bmp, jpeg, gif) I do believe TinyCAD is the best out there. Short learning curve (unless you are going to SPICE model) and near instant gratification.  If you need to SPICE model, place components on a board then Eagle is possibly one of the most popular. Certainly there are others but these two, TinyCAD and Eagle have a huge following and access to other users is a big plus.

As mentioned before, there is going to be a learning curve.  If you are going to purchase make sure you can at least have a trial run. In my own experience I can use TinyCAD to place at least 30 components, a copy of a schematic for instance, in under 30 minutes.

SPICE modelling will teach the user many aspects of how “not” to do it.  This relates to “it just doesn’t work” yet you know the circuit to be tried and trusted.  As one gets more familiar with the idiosyncrasies of the program used (and they all have idiosyncrasies, often user related) the quicker one gets around to breadboarding.

My first PCB was a long, tedious process of tracing, photo-resist, sunlight, copper etch (Ferric Chloride).  Laser printers in those days were upwards of R10 000.00.  A thirty component layout of a superhet receiver took the better part of a day.  No UV oven but plenty of sunlight.

  • Nowadays we use a laser printer and transfer paper (circuit layout).
  • Cleaning materials (shine up the board – you will need to apply some elbow grease)
  • Hot iron to transfer the ink to copper
  • Copper etch (in South Africa Ferric Chloride is a popular choice).

Assuming you have stolen your layout from the web somewhere this entire process can take only as long as the strength of the etching solution. Of course you cannot throw any form of etching solution away – it’s classed as a hazardous material.

Stop! Wait! Achtung!

When mass producing boards sometimes it’s best to use a professional service such as Deman Manufacturing or Trax.  No affiliation, there are quite a few companies in South Africa offering these services.

To RoHS or not to RoHS? ( Restriction of Hazardous Substances).  I have had the displeasure of working on computer motherboards when this cursed RoHS legality kicked in and when replacing North or South-bridge chipsets (or CPU sockets, or etc, etc) even very experienced Ball Grid Array machine users had a terrible time getting a hang of replacements without burning the board or adjacent components.  Yes, times have changed but if you need to go the RoHS way look at a professional service company. This is my opinion, not necessarily yours. In South Africa commercial manufacturing of PC boards and the populating of components you may have no choice.

High speed switching circuits may sometimes be easy to comprehend but when it comes to board layout, experience is key.

Multi-sided, multi-layered boards.  Yes, it has been done at home but the reality is that most DIYers don’t usually venture into anything above double sided boards.

Military, aeronautical and space.  For avionics and military, components and board manufacture is designed to function under extreme conditions.  The manufacturing process requires certified engineers and artisans.

Do try to get a free tour through a modern manufacturing facility like Samsung or Hisense.  The Hisense factory in Atlantis has on previous occasions allowed guided tours through their factory.

Further reading:

The tin whisker

Quoro –Disadvantages of lead free solder Vs lead solder?   Summing up the problem.

 

 

 

 

 

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