Some Common Issues Identified During PCB Design Process

2019/1/25 14:34:24

For designers or hobbyists, no matter what kind of software do you use for the design work, there are some common issues that may occur during the design process, Today in this essay, we will talk about ten common issues.

Overlapped pads

1. The overlapped pads will obviously lead to overlapped vias, during the PCB fabrication process, vias may hurt or break if it is repeated drilled;

2. For multi-layer boards, once there is overlapped vias, and there is isolated pads and flower pads, the finished pads show in the film will be isolated ones, the boards will be rejected during fabrication process.

narrow pads

Miss-use of layers

1. Some useless traces may be connected on some layers, for example, only top layer, inner layer 1, inner layer 

2. bottom layer are required for four-layer design, but some designers may accidently put a fifth layer inside;

3. For Protel software, it would be unacceptable to draw the trace with board layer, and mark the layers with board layer, this may lead to short circuit and cause defective designs;

4. Some designers may make some strange designs, for example, the component side is accidently put in the bottom layer, and put solder side on the top one.

Silkscreen issues

1. The silkscreen may overlapped with SMD pads, and this is very inconvenient for electronic test and component soldering;

2. The text is too small on the boards, this would cause blurred or overlapped text, which makes it difficult to identify the text.

Vias diameter for single-sided pads

1. Drilling is normally not required for single-sided pads, it would better to specify if required.The via diameter should be set as zero. For if there is any data created, the via drawing appears on the design and thus causing issue;

2. Please specify the requirement if drilling is required for single-sided pads.

Fill the pads

Normally we will use DRC to check the filled pads, while consider about the fabrication process, this does work. Because the pads do not generate solder mask data, and the solder mask oil will be covered by the pads, and make it difficult to solder the component parts.

isolated pads

Flower pads and continuous trace exist on ground layer
Because the flower pads on plane and ground layers are mirrored in the design, all the related traces are isolated. And be careful of the isolated traces in case of any short circuit.

Unclear names 

1. For a single-sided boards, if the layer names are incorrect ,the finished boards may mirrored completely;

2. For a four-layer designs, the standard layer sort should be TOPmid1, mid2 bottom, while if you have intentionally designed with another sort, it would be better to specify, otherwise the finished boards will be defective ones.

Too much filled area

1. It is not a good idea to fill the pads too much or use thin trace to fill the area;

2 .We may miss data with this design, or lead to incomplete trace data;

3. The excessive filling area will make it more difficult to deal with the design data .

The pads on SMD is too short

The issue applies to electrical test, for overpopulated pads, the space for the IC is too small, and when assembly is performed, we have to install flying probe, with narrow pads, it makes more difficult to install the probe.

fill the pads

Narrow space for net trace

Once the space for trace is less than 0.3mm, during the PCB fabrication process, some broken film used for etching may be remained on the boards, and cause circuit short.

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