Posts Tagged ‘etch’

Etch Factor

Sunday, February 10th, 2013

An etch factor or etch compensation is a process modification made by the Printed Circuit Board (PCB) manufacturer to compensate for the chemical etching process. The chemical etching process is a subtractive operation that removes copper gradually when forming the circuit pattern. The size of the features at the end of the process are smaller than the size of the features at the beginning of the process. When a PCB design requires a track width of 0.005″ (0.127 mm) the PCB manufacturer has to start out with a wider track. The amount the track is increased by is referred to as an etch factor or etch compensation. The etch factor is also proportional to the thickness of the copper or copper weight weight being removed. The more copper being etched through the larger the etch factor.

Etch factor added with CAM tool.

Etch factor added with CAM tool.

The fact that the PCB manufacturer has to increase the feature size to compensate for their manufacturing process is critical for a PCB designer to understand. The designer must provide enough spacing in their design for the PCB manufacturer to process the design. In other words, the minimum spacing in the design must meet the manufacturer’s minimum space that they may consistently process. In PCB manufacturing there are three types of spacing that we consider. They are… (more…)

Inner Layer Pre-Clean

Sunday, May 15th, 2011

Inner layer processing requires Dry Film Photo Resist to be laminated onto the copper surface. The dry film is resolved into a circuit pattern. Copper we want to keep is protected by the circuit pattern from the etchants used to remove the copper. The bond of the dry film to the copper surface must be strong enough so that the film does not come of when in the etchant chemistry. Copper foil such as RTF, Reverse Treated Foil, are rough enough so that the dry film forms a good bond to the copper as is. Many copper foils are not rough enough or are supplied with a contaminated surface. In these cases the foil must be (more…)