Using a Hot Air Rework Station for PCB Repair

Using a Hot Air Rework Station for PCB Repair

By Matthew Burris   Shared by Erin KOU

Hot air rework stations are an incredibly useful tool when building PCBs. Rarely will a board design be perfect and often chips and components need to be removed and replaced during the troubleshooting process. Attempting to remove an IC without damage is nearly impossible without a hot air station. These tips and tricks for hot air rework will make replacing components and ICs much easier.

The Right Tools

Solder rework require a few tools above and beyond a basic soldering setup.

Basic rework can be done with only a few tools, but for larger chips, and a higher success rate (without damaging the board) a few additional tools are highly recommended. The basic tools are:

1. Hot air solder rework station (adjustable temperature and air flow controls are essential)
2. Solder wick
3. Solder paste (for resoldering)
4. Solder flux
5. Soldering iron (with adjustable temperature control)
6. Tweezers

To make solder rework much easier, the following tools are also very useful:

1. Hot air rework nozzle attachments (specific to the chips that will be removed)
2. Chip-Quik
3. Hot Plate
4. Stereomicroscope

Prepping for Resoldering

For a component to be soldered on to the same pads where a component has just been removed requires a little preparation for the soldering to work the first time. Often a sizable amount of solder is left on the PCB pads which if left on the pads keeps the IC raised and can prevent all of the pins from being correctly soldered. Also if the IC has a bottom pad in the center than the solder their can also raise the IC or even create hard to fix solder bridges if it gets pushed out when the IC is pressed down to the surface.

The pads can be cleaned up and leveled quickly by passing a solder free soldering iron over them and removing the excess solder.

Rework

There are a couple of ways to quickly remove an IC using a hot air rework station. The most basic, and one of the easiest is to use, techniques is to apply hot air to the component using a circular motion so that the solder on all of the components melts at about the same time. Once the solder is melted the component can be removed with a pair of tweezers.

Another technique, which is especially useful for larger ICs is to use Chip-Quik, a very low temperature solder that melts at a much lower temperature than standard solder. When melted with standard solder they mix and the solder stays liquid for several seconds which provides plenty of time to remove the IC.

Another technique to remove an IC begins with physically clipping any pins the component has that are sticking out of it. Clipping all of the pins allows the IC to be removed and either hot air or a soldering iron is able to remove the remains of the pins.

Dangers of Solder Rework

Using a hot air solder rework station to remove components is not entirely without risk. The most common things that go wrong are:

1. Damaging nearby components - No all components can withstand the heat required for removing an IC over the time period that it can take to melt the solder on the IC. Using heat shields like aluminum foil can help to prevent damage to near by parts.
2. Damaging the PCB board - When the hot air nozzle is held stationary for a long time to heat up a larger pin or pad the PCB may heat up too much and start to delaminate. The best way to avoid this is to heat up components a little slower so that the board around it has more time to adjust to the temperature change (or heat up a larger area of the board with a circular motion). Heating a PCB very rapidly is just like dropping an ice cube in to a warm glass of water - avoid rapid thermal stresses whenever possible.

For PCB needs, welcome to contact Erin KOU(erin.kou@pcbway.com)

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PCBWay - Low Cost PCB Manufacturer

PCBWay - Low Cost PCB Manufacturer

Edit by Erin KOU [www.pcbway.com/e]

Prototyping PCBs has become much easier over the last few decades as software and services have been developed that help make low cost and high quality PCB prototyping possible. PCB design software, or EDA software, is available that is simple to use and offers advanced capabilities and features that speed design and reduce errors. Many of the free PCB design packages are offered by PCB manufacturers that offer affordable low volume PCB prototype manufacturing which is often a great alternative to making a PCB at home.

Making PCBs at home, while it can be very affordable, imposes several limitations. Typically thin traces are very hard to make reliably, vias or plated through holes must be manually installed as miniature rivits or soldered in wires or not used at all, and multilayer boards are not possible. The limitations imposed by homemade PCB manufacturing are addressed by even the lowest cost PCB manufacturer.

Limitations

Even though PCB Prototyping services address many of the limitations of homemade PCBs, they do not include the most advanced features and tightest specifications. While the typical PCB capabilities are quite good, with trace widths as small as 6 mils, the most advanced components, such as dense BGA components, are too demanding for the PCB manufacturer options and full service PCB manufacturing solutions will be needed. Also, board layers are often limited to two layers and at most 4 layers before prices begin to go up substantially. For the most part, a four layer PCB prototype will suffice for all but the most demanding hobbiest work.

PCBWay, PCB Prototype the Easy Way

With more than A decade in the field of PCB prototype and fabrication, we are committed to meeting the needs of our customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers in China, we pride ourselves to be your best business partners as well as good friends in the every aspect of your PCB needs.

Quality:

As the circuit boards are manufactured, and also after they are complete, we subject them to strict tests and monitoring: E-testing   X-ray (layer offset check)   China based PCB manufacture and electronic assembly factory  A.O.I. testing (Automated Optical Inspection)

Delivery:

Through the years we are proud to have been keeping an on-time delivery rate of 99%. We know, apart from PCB quality, theother most important factor is the shortest possible lead-time, which is crucial for engineers' R&D works, especially in the stage of prototyping. We work in three shifts to make sure your PCBs will be on your desk as agreed up and as early as possible.

Pricing:

Our pricing structure is transparent and has no hidden cost in it. Our price is one of the most competitive in the world, and is just a fraction of what other American or European fabricators normally charge you. Even many price-sensitive customers like students and hobbyists largely rely on us for their PCB prototype and fabrication orders. We try our utmost to save your money and time.

contact Erin KOU - erin.kou@pcbway.com

How to generate Gerbers from Eagle files

Generating Gerbers

shared by Erin KOU (www.pcbway.com/e)

When you’ve finalized your design, the last step before sending it off to the fab house is to generate gerber files. Gerber files are kind of a “universal language” for PCB designs. EAGLE is far from the only PCB CAD software out there, and its design files are nothing like those of Orcad or Altium. Fab houses can’t possibly support every piece of software out there, so we send them the gerber files instead.

Gerber files – note the plurality – each describe single layers of the PCB. One gerber might describe the silkscreen, while another defines where the top copper is. In all, we’ll generate seven gerber files to send to the fab house.

CAM Processor

Before we get too much further, you’ll need to download another definition file: PCBWAY’s CAM file.

Then, load up the CAM processor by clicking the CAM icon – 

From here, go to the File menu, then go Open > Job…. In the file browser that opens, select the sfe-gerb274x.camfile that you just downloaded. Now the CAM processor window should have a series of tabs: “Top Copper”, “Bottom Copper”, “Top Silkscreen”, etc. Each of these tabs define how to create one of the gerber files. Now all you have to do is click Process Job. If you haven’t saved recently, it’ll prompt you to.

The gerber generation process should be pretty quick. Once it’s run its course, have a look in your project directory, which should have loads of new files in it. In addition to the board (BRD) and schematic (SCH) files, there should now be a .dri, .GBL, .GBO, .GBS, .GML, .gpi, .GTO, .GTP, .GTS, and a .TXT. Meet the Gerbers!

Gerber File	Extension
Bottom Copper	GBL
Bottom Silkscreen	GBO
Bottom Soldermask	GBS
Top Copper	GTL
Top Silkscreen	GTO
Top Soldermask	GTS
Drill File	TXT
Drill Station Info File	dri
Photoplotter Info File	gpi
Mill Layer	GML
Top Paste	GTP

Delivering the Gerbers

The process of sending gerber files varies by fab house. Most will ask you to send them a zipped folder of select files. Which gerber files? Check with your fab house again (e.g. Advanced Circuits and OSH Park’s guidelines), but usually you want to send them GTL, GBL, GTS, GBS, GTO, GBO and the TXT files. The GTP file isn’t necessary for the PCB fabrication, but (if your design had SMD parts) it can be used to create a stencil.

So zip those gerbers up. Play the waiting game. And get ready to assemble your very own PCB!

PCB Tutorial - Gerber Files

PCB Tutorial - Gerber Files

Shared by Erin KOU 



Link: https://www.youtube.com/watch?v=B2FVH5szE6s

PCB Design Tutorial: Final steps of PCB design and the generation of fabrication outputs (Gerber files and NC drill files) using Altium Designer/DXP/Protel.

PCB design: Basic PCB Composition

Basic PCB Composition

Sourced by EEWEB, Editor by Erin KOU （PCBWay）

Here are four basic composition of a Printed Circuit Board.

Substrate: 

Figure 1  PCB Composition

Figure 2  Substrate

The base material, or substrate, is usually fiberglass and its most common designator is “FR4”. This solid core gives the PCB its rigidity and thickness. Cheaper PCBs and perf boards will be made with other materials such as epoxies or phenolics which lack the durability of FR4 but are much less expensive.

Copper:

Figure 3  Copper

The next layer is a thin copper foil, which is laminated to the board with heat and adhesive. On common, double sided PCBs, copper is applied to both sides of the substrate. When we refer to a double sided or 2-layer board we are referring to the number of copper layers. This can be as few as 1 layer or as many as 16 layers or more.

Soldermask:

Figure 4  Solder Mask

The layer on top of the copper foil is called the soldermask layer. This layer gives thePCB its green color. It is overlaid onto the copper layer to insulate the copper traces from accidental contact with other metal, solder, or conductive bits. Soldermask is most commonly green in color but nearly any color is possible.

Silkscreen:

Figure 5  Silkscreen

The white silkscreen layer is applied on top of the soldermask layer. The silkscreen adds letters, numbers, and symbols to the PCB that allow for easier assembly and indicators for humans to better understand the board. Silkscreen is most commonly white but any ink color can be used. Black, gray, red, and even yellow silkscreen colors are widely available; it is, however, uncommon to see more than one color on a single board.

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PCBWay: Easy way making your PCBs

For PCB needs, welcome to contact Erin KOU(erin.kou@pcbway.com)

PCB Design for manufacture

Design For Manufacture

Shared by Erin KOU (www.pcbway.com/e)

Electronics products almost invariably have a Printed Circuit Board , PCB, on the inside. This is one of the most common things we do, designing the Printed Circuit Board on the inside on the product. Now designing a Printed Circuit Board so it works correctly is one thing, but if you are going to make them cost effectively in volume then you have to consider the manufacturing options at your disposal. To achieve Low Cost Electronics Manufacture requires every aspect of the design to be considered. The following video covers the basic issues very well:

https://www.youtube.com/watch?v=VXE_dh38HjU

So the things to focus on are:

• Use SMT as much as possible,
• Reduce the number of components by using more highly integrated circuits,
• Reduce the variety of components so the number of reels is reduced,
• Ask the PCB loader about their standard panel sizes.  If you can adjust the PCB size to suit them then it will reduce their costs,
• Work with component types that the PCB loader can handle
• Work with components that you can buy in suitable quantities

PCB Layout - PCBWay

PCB Layout

By Ray Keefe Shared by Erin KOU (www.pcbway.com/e)

After the Schematic Capture component of the Electronics Design  is complete, the logical connections for the electronics components have been determined. If the Electronics CAD package also supports it, you can add rules to guide the Printed Circuit Board Layout, also abbreviated to PCB Layout which we will use from here on.

The PCB provides both the mechanical support for the components and is many cases is a critical part of the circuit since the length of tracks, their thickness, their clearance from other tracks and the relative placement of components and tracks can significantly influence the final performance of the PCB. This is particularly true as power levels, clock speeds or frequency increases.

The Electronic Schematic defines the electrical connections between components, the value of components such as resistors, capacitors and inductors, the type of semiconductors used (silicon chips) and the connectors that take signals and power on and off the PCB. Each item on the schematic has to be linked to a physical shape that will go onto the PCB. This is done by assigning a footprint to the schematic item.

Schematic Symbol

I will explain  it works. The Schematic Symbol for an FT232RL USB Serial Interface device is shown below. This is arranged with the signals conveniently placed to suit logical connections and to make the overall Schematic easy to read and understand.  The signal name is shown inside the symbol boundary, and the pin number of the IC package is shown on the outside. 

FT232RL Schematic Symbol

Schematic Circuit

So this  is the symbol for a single part, an IC or Integrated Circuit. The Schematic Circuit or Electronic Schematic shows the connections to the other parts of the circuit. Below we see USB connector wired up the the FT232RL IC and the power supply bypass capacitors. The logic level UART signals are shown at the top right. This section of the Electronic Schematic provides the logical connections for a USB serial interface.

FT232RL USB Schematic

PCB Footprint

 Before we can do the PCB Layout, we have to associate the PCB Footprint each Schematic Symbol will use. The PCB Footprint for the FT232RL IC is shown below.

FT232RL PCB Footprint

This is one of the 2 possible footprints for the FT232RL. This one is a 28 pin SSOP package.

Once each Schematic Symbol has a PCB Footprint, we are ready to do the PCB Placement.

PCB Placement

 The first step is to create the outline for the PCB and its mounting points, then to place each PCB Footprint so it is in the correct place. For some components, such as connectors, there is a specific place it must go. For other components, there is more freedom to choose the position and there are groups of components that must be in a specific relationship to each other. An example of this are the power supply bypass capacitors which must go very near to the IC they are supporting.

An example of a completed PCB Placement is shown below. This is a USB to RS232 serial converter.

PCB Unrouted

PCB Routing

Now we have the components where we want them, we turn on the autorouter and the PCB is finished. Sorry but I couldn't help that. The autorouting features of most PCB Layout CAD software packages are never as good as doing it yourself. They can be useful for testing the ease of routing for a particular placement. There are a lot of manufacturing considerations that need to be taken into account and track size requirements, either for current carrying or voltage drop, can be hard to define from just the schematic. And example of this is the main system voltage such as VCC. In some parts of the circuit the required current is low so smaller track sizes are OK, whereas other areas need heavier tracks. It isn't easy to define this at the schematic level because they are all the same signal or Net.

The PCB with the routing complete is shown below. The selection of track size is related to the current the circuit needs to carry. A good reference for determining the track size is provided by the standard IPC-2222A.

PCB Routed

PCB 3D Cad Integration

 It is also important to make sure the PCB will fit into a mechanical enclosure. Most modern PCB CAD tools, such as Altium Designer which we use, can create full 3D models of the PCB. Shown below is an example of just the PCB without the components showing.

3D PCB View

 So there we have it. A PCB taken from the completed Electronic Schematic through to a PCB Layout.

 Next we will look at prototyping our new PCB.

PCB design: The different kinds of Vias used in PCB designs

The different kinds of Vias used in PCB designs

  Vias are used as electrical connections between layers on a PCB (printed circuit board). They can carry signals or power between layers.

Here are the types of Via configuration that we can encounter in a PCB design:

Stub Via

     The Stub Via is the most common via configuration found in PCBs aside from the Through hole Vias. The two variations of a stub vias are illustrated as Stub Via A and Stub Via B.

Figure 1  Stub Via A

     For the Stub Via A example, it shows the through portion starting from the top layer and ending at some inner layer. The stub portion is the remaining portion continuing from the inner layer junction to the bottom layer.

Figure 2  Stub Via B

     The Stub Via B example shows the through portion originating from one internal signal layer and terminating on another internal signal layer. In this scenario, there are two stubs. The first stub is from the first internal layer junction to the top layer; the second stub is from the second internal layer junction to the bottom layer.

Through Hole Vias

Figure 5  Through Hole Via ( Image courtesy en.wikipedia.org )

     Through vias are the oldest and simplest via configurations originally used in 2-4 layer PCB designs. Since the signals originate and terminate from the outer layers of the PCB, there are no stubs. In multi-layer PCB applications, they are an inexpensive way to eliminate the resonance effects caused by stubs where other mitigation techniques are not practical or are too expensive.

Blind Vias

Figure 3  Blind Via ( Image courtesy www.microconnex.com )

     Blind vias are just like any other via, except that they don’t cross through the entire PCB. A Blind Via connects one or more internal layers to only one external layer. Controlled-depth drilling is used to form the holes prior to plating.

Buried Vias

Figure 4  Buried Via

     A buried via, is a plated hole which is completely buried within the board. It connects one or more internal layers and does not connect to an external layer. A disadvantage of using buried via technology is that it is expensive since the inner layers being interconnected need to be fully fabricated and plated before final lamination of the entire PCB.