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EQ’s for a variety of printed circuit board design files are common to PCB Global’s Computer Aided manufacturing (CAM) Engineering department. We will invariably have a few Engineering Questions to confirm with our customers, such as the example shown below regarding Solder Mask Bridges.

Solder Mask Bridges

EQ from CAM:

These SMT pads do not have enough space between them to apply a correct solder mask dam. This area will be completely free of solder mask, or can be shaved by 2mil from each SMT pad then apply the solder mask between each section.

Explanation:

Currently this SMT area has the solder mask open as one block. This is an acceptable clearance; however, it can cause shorts between these pads after SMT reflow. By shaving 2mil from each SMT pad, we can ensure there is sufficient distance to allow for exposure of the solder mask file, to apply solder mask between each SMT pad. This ensures the solder mask dam will improve the solder reliability yield after SMT reflow.

The actual distance between SMT pads differs depending on the finished copper thickness/ Below is an example of 1/2/3 & 4oz copper finish:

Solder mask bridge for 1oz copper (4mil)

Solder mask bridge for 2oz copper (5mil)

Solder mask bridge for 3oz copper (6mil)

Solder mask bridge for 4oz copper (6mil)

 Resolution:

With authorisation from our customer, the SMT pads in question had the copper area shaved 2mil allowing a solder mask dam between these IC’s.

For further tips and information when designing and laying out your printed circuit board design file please do not hesitate to contact our PCB Global team at sales@pcbglobal.com

Engineering Questions or EQ’s are very common with new printed circuit board files and designs. PCB Global’s Computer Aided manufacturing (CAM) Engineering department will invariably have a few EQ’s depending on the quality and consistency of the files provided. One example of a typical EQ regarding Hole to Track clearance is shown below:

 

Hole to Track Clearance

EQ from CAM:

This non plated through hole (highlighted in green) is only 5mil from the track. The absolute minimum distance is 6mil.

Explanation:

Non plated through holes are drilled at the final stage during CNC routing. The close proximity of these holes shown in the file are too close as the copper tracks and copper pads may place stress on the copper area during the CNC non plated drilling process, resulting in a weak point.

Resolution:

With approval from our customer, the track to non-plated through hole violation was resolved by amending the track travel (highlighted in red) which resulted in a 12mil clearance.

For further tips and information when designing and laying out your printed circuit board design file please do not hesitate to contact our PCB Global team at sales@pcbglobal.com

Posted on 25/03/2016

With the large variety of specification required in creating your Printed circuit boards, PCB Global’s Computer Aided manufacturing (CAM) Engineering department will invariably have a few Engineering Questions (EQ’s) to confirm. One example of a typical EQ relating to Stub Track is shown below:

Stub Track

EQ from CAM:

Stub track that leads to nowhere and has no hole as a through connection.

Explanation:

Small copper stubs that end with a dead end no connection are generally not a problem to fabricate, however, we need to ensure that no via or other connection has been omitted.

Resolution:

With confirmation from our customer this stub track was deleted resulting in a clean pad finish and the net was terminated at the via.

For further tips and information when designing and laying out your printed circuit board design file please do not hesitate to contact our PCB Global team at sales@pcbglobal.com

It is common practice that PCB Global’s Computer Aided manufacturing (CAM) Engineering department will invariably have a few Engineering Questions, also know as, EQ’s to confirm. One example of a typical EQ concerning V-Cut Through Tooling Holes is shown below:

V-Cut Through Tooling Holes

EQ from CAM:

V-grooving lines cutting through the tooling holes on the tooling strips.

Explanation:

The customers panellised files were set up with the v-grooving cutting through the tooling holes. V-grooving must be designed to avoid cutting through tracks, pads, holes and all copper plane areas. As a rule, it is best to have all v-cuts on bare fibreglass only (see below).

Resolution:

With confirmation from our customer both these two tooling holes were moved 10mm to the left to avoid the v-cut.

For further tips and information when designing and laying out your printed circuit board design file please do not hesitate to contact our PCB Global team at sales@pcbglobal.com

PCB Global’s CAM Engineering department will invariably have a few EQ’s to confirm. This is dependant on the quality of the PCB design file package received. See below example of a typical EQ for plated and non-plated through holes:

Plated (PTH) and Non-Plated (NPTH) Through Holes

EQ from CAM:

Holes noted as plated through holes do not have any pads and holes with pads are noted as non-plated through holes.

Explanation:

Generally, holes that have no pads should be non-plated through holes as without a pad landing on the top and bottom layer, the hole wall integrity can be compromised. This causes weakening as chemical solutions can seep into these areas, reducing the long term reliability of the PCB.

With the non-plated through holes with pads, although this is not uncommon, it is still a EQ that is frequently asked. These holes are best fabricated with a copper pull back from the edge of the hole (about 10mill) to ensure that there are no copper burs after drilling.

Resolution:

With confirmation from our customer both these hole types were fabricated as non-plated through holes and the non-plated through holes had the copper pulled back 10mil to ensure quality of the PCB.

For further tips and information when designing and laying out your printed circuit board design file please do not hesitate to contact our PCB Global team at sales@pcbglobal.com

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