Easy to follow guide on making PCB by using photo etching method

Still struggling with various PCB making technologies and cannot do it right, you should try Photo Etching method which is becoming more and more common among radio amateurs. All materials needed are easily accessed. Probably the hardest part is to obtain UV light source. But you can find tons of sources on the internet how to build one.

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Printed Circuit Board (PCB) Technologies

The term circuit technology usually refers to the various techniques that used in the manufacture of electrical circuits. A large number of devices that are used today make use of printed circuit boards (PCBs). These devices provide a mechanical support for the various components present within the given device and also, the electrical connections between the components. The electrical connections present on the PCB are made out of copper sheets that are laminated on a non-conducting material. Initially a large copper sheet is laminated on the board and then the sections that are not required are removed. Various techniques are used for removal of unwanted copper. Some of them are: Silk Screen Printing: In this technique, an etching resistant ink is applied on those areas that are required and the remaining part is etched off. Photoengraving: Here a photo mask of the circuit required is prepared using desired software and then, it is applied onto the blank PCB. After this the portions that are not required are etched off. PCB Milling: In this technique, a mechanical milling system that can work on 2 or 3 dimensions is used to remove the copper. The milling system is controlled by software.

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Surface Mount Soldering with inexpensive equipment

This is an excellent video about SMD soldering using cheap and straightforward equipment that most electronics hobbyist can find at home. This 9 min video tutorial prepared by CuriousInventor includes up-close shots of fine pitch soldering such SMD elements as 603 resistors, PLCC< 44 pin QFP, 208 pins fine-pitch QFP. Also, there are few SMD desoldering tips disclosed.

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Eagle CAD PCB footprints for audio processors TDA7313 and TDA7315

TDA7313 and TDA7315 are digital controlled audio processors that can be used in applications where digital control of audio is needed. TDA7313 and TDA7315 are are pretty same just TDA7313 is more complex by hawing 3 stereo input channels and two outputs (front and rare). Both chips have volume control (step=1.25dB), tone (bass and treble) balance, independent faders for each output processors. Also there are loudness functionality. TDA7313 and TDA7315 have low distortion, low noise, that makes them ideal for quality audio applications for car audio and Hi-FI systems.   Both chips can be controlled by MCU via I2C(TWI) protocol. This makes easy to interface microcontrollers with additional features like LCD, buttons. Or simply control directly from PC using RS232 or other interface. Both chips can be found in DIP or SO packages. Here are Eagle libraries of both digital audio processors that I have made. tda7315.zip(2kB) tda7313.zip(2kB) I have intent to make control board with TDA7315 with LCD and button control using Atmega8 microcontroller.  

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PCB Exposure using UV light LED box

I came across this interesting project. The guy decided to make UV PCB exposure box made of UV light LED’s. The main reason why he used LED was the power dissipation and compactness. Assuming that one UV tube would take about 6W while one UV LED would take about (20mAx3.2V=64mW). Most of that energy UV tubes dissipate as heat energy. So he took: 54 x UV LEDs of 400nm (6000 – 7000 mcd) – 100 units in Ebay costed 12€; 18 x 68ohms resistors 1/4W – 0,36 €; 1 connector – 0.50€; 1 electrolytic condenser of 2200uF – 30v; 1 Eurocard Plate 100×160 about 5 € ;  

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Place electronics parts correctly on PCB

Lets go through few examples how to place electronic parts correctly on PCB board. SMD electronic parts especially if lead pitch is above 1 mm, then placement of leads has to be symmetrical on copper planes: If IC has smaller lead pitch like 0.5 – 0.8mm positioning by hand become harder. Sometimes it is recommended to use special glue to fix SMD part before soldering. DIP electronic parts has to be soldered as close to PCB board as possible to make them stand stabile and to avoid heat resistance. Electronic parts with axial leads are placed vertically for better air ventilation. Because of this diodes and Zener diodes has to mounted with cathodes up with gap of 1-2 mm between electronic part and PCB board. If there is enough place – they can be mounted horizontally. This way between electronic part and PCB has to be a gap of about 1 – 2 mm. Single side pin electronic components like ceramic, electrolytic capacitors, crystals, semiconductor fuses have to be placed with minimal gap (about 1 mm) between PCB. H49U crystals have to be placed with minimal gap between PCB. It under resonator there is no via holes or tracks, then…

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