How to Fix a PCB? Beginner’s Guide

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Electronic boards, also known as printed circuit boards (PCB), are present in everything that involves technology, from the complex control panel of an airplane to the apparently simple remote control of a television. In this guide we shall learn how to fix a pcb?

These electronic boards can become damaged over time due to physical shock, oxidation or moisture, requiring electronic board repair. Learn more features of electronic boards, and how to repair electronic boards.

Features and repair of electronic boards

Electronic boards basically consist of a board of plastic and fibrous materials with thin films of metallic substances. These films are called tracks or tracks, and are responsible for conducting electric current through the electronic components, making them interconnected in a single system.

Each electronic board is unique, with different components and functionality. What does not change between them is the fact that, if they are damaged, all the equipment will have problems. Therefore, it is very important that the electronic boards are repaired, so that the equipment works correctly again.

However, as we have seen, each board is unique, and companies and professionals without sufficient experience and training can repair electronic boards that, instead of fixing the problem, can damage the system even more. It is essential to choose a serious, responsible company that provides a quality service to repair electronic boards in the best possible way.

Simple Steps to Fix A PCB

Below we present you, in a few steps, the process of repairing a printed circuit board damaged by long-term oxidation of copper (sweat) due to corrosion caused by the presence of water within the damaged part of the board.

Such damage, despite appearances, is a very common phenomenon and occurs mainly on PCBs not protected with an anti-adhesive protective layer (e.g. polyurethane), as it was in this case.

Sometimes corrosion can also be observed on the protected plates as a result of long-term exposure of the device to a hostile environment with a critical level of humidity, in such cases it mainly concerns damage to connectors, connectors, or even other massive elements, the protection of which is difficult or not at all possible.

A quick visual diagnosis made it possible to determine the area and type of damage, which in turn resulted in planning and taking specific service activities aimed at removing the defect.

The appearance of a fragment of the board before starting the repair

As can be seen above, the integrated circuit responsible for serial communication was damaged, along with the accompanying elements C36-C38 and C34.

These elements have been selected for replacement, and additionally, the following must also be replaced: the C35 filtering capacitor (the beginnings of corrosion are already visible on it), the R30 resistor and the nearby 6-pin terminal block (it requires desoldering due to visible leaks under its housing) ).

The condition of the board after removing most of the elements selected for replacement and securing the adjacent parts of the board (including delicate and not resistant to high temperature IDC connectors) with a Capton type protective tape, whose task is to protect the operational elements against possible damage, mainly thermal, during e.g. hot air soldering.

In photo 3, we can additionally notice numerous pitting and damage to the corroded pads (soldering points of SMD components), the efficiency and electrical properties of which will be restored in the course of further repair activities.

PCB Board

The layout of tracks and pads prepared for soldering new parts

We can see the reconstructed pads of most of the elements that need to be replaced. The whole thing has been coated with a suitable gel flux and the pads are prepared for soldering new parts on them.

Both the desoldering of damaged and new SMD electronic components was performed using a mixed technique. For this purpose, both a low-power heater soldering iron equipped with a pin (needle) tip with a tip diameter of less than 0.2 mm was used, as well as the hot-air soldering technique with a round nozzle with a standard diameter, the station is equipped with temperature stabilization and flow.

How to desolder terminal block in a pcb?

The 6-pin terminal block was desoldered using a heater soldering iron with a "screwdriver" tip (1.2mm fin width) and a Weller automatic suction device with a 2.5mm diameter tip. In the desoldering process, a preheater (infrared heater) with a process temperature of approx. 200 degrees C was also used.

 The use of this tool was convenient due to the lack of SMD components on the board from its bottom (bottom), which significantly accelerated the process.

The process temperature of the upper layer of the plate (element layer - top), both during desoldering and soldering of the elements, did not exceed 440 ° C. and was dictated by work with a lead-free binder, which was a factory soldered repaired plate.

During reworking (replacement of damaged parts), tin with the addition of lead, "tinol" type, at the operating temperature of 325 ° C was used, which is in line with the RoHS directive, which allows the use of such tin in repairing electronics.

View of the slab after repair

The photo above shows the board after soldering the elements, pre-washing the excess flux and checking the electrical connections. As you can see, a new rail socket has also been soldered in, and the protective tape has already been removed.

After thoroughly washing and drying the board again, it will be ready for functional tests carried out under workshop conditions, before sending it to the customer for commissioning on the machine.

It should be remembered, however, that not all types of damage to such a plate are repairable and economically viable.

 The main reasons for not qualifying for the service are:

  • damage to components that prevent their identification, in which, despite the analysis of the system and based on our own experience, we are not able to determine the type of the damaged part
  • damage to the vias (vias) on multi-layer panels, where the connection between one of the invisible (internal) layers has been damaged
  • some broken path connections on one of the inner layers
  • massive, extensive damage to the board, including many layers of paths and damage to the laminate (PCB canvas), caused e.g. by fire or very high temperature acting in a spot.

Insulation in PCB Board

When you add a layer of debris to a PCB, you are essentially adding a layer of thermal insulation material to the board's substrate. Because the board draws current, the generated heat cannot properly dissipate over the surface of the substrate material.

 This will lead to heat sinks which will likely lead to catastrophic failure in key board components.

Pollution - when there is a pollution event that results in electrical connections where electrical connections should not be. Namely, a short circuit is where a contaminant, usually water, bridges the current, which damages other components in the circuit.

Beware of these threats and fix the damage they cause so you can be productive and have the right devices to keep your work running. Read on to find out how to clean your circuit boards while still being safe.

How do boards get dirty?

Printed circuit boards are found in almost all electrical devices, including computers and industrial equipment. Over time, water, dust, and dirt can infiltrate the devices and cause you to take steps to prevent permanent damage to the equipment.

Fans, which are responsible for keeping the equipment cool in order to function properly, can draw in debris found in the air and any dirt that has landed on adjacent surfaces. Accumulation of unwanted materials leads to overheating and component failure.

Liquid like water is not as bad for electronics as the additives it almost always contains. Even ordinary drinking water contains ions such as sodium chloride and a variety of other minerals that enhance its response to electronic devices.

As soon as a liquid with good conductive qualities comes into contact with an active device, electrical connections pass through currents into deactivated areas of the PCB, which can lead to a short circuit. This harms the power circuit and damages your device.

Board cleaning prevention and safety

To avoid dirty boards, you can take preventive measures. Get into the habit of having any unused electronics set to the "OFF" position, as the chance of adverse effects caused by water damage is greatly reduced if the affected areas dry out before work resumes.

Be careful when handling printed circuit boards:

  • Disconnect the device from the power source
  • Avoid standing near water
  • Wear dry clothing

Disassembling equipment can be hazardous to electronics, so make sure you understand how to properly handle the devices you are working with and how to put them back into working order.

How do you clean circuit boards?

PCB cleaning effectively depends on using the right methods and tools. The easiest ways would be to use:

  • Compressed air;
  • Baking soda;
  • Isopropyl alcohol;
  • Distilled water
  • Household detergents;

Use a soft brush and a lint-free cloth so that nothing is damaged.

Summary

In many cases, when we refer to this type of failure in a work order, maintenance personnel will want to know how this failure can be prevented and equipment fault tolerance increased.

Cleaning a circuit board may seem like a daunting task, but these boards get dirty all the time. Many different materials are hazardous to the performance and safety of these devices.

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