Archive for the ‘Fabrication Process’ Category

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…)

Dry Film Lamination (history)

Sunday, September 23rd, 2012

Dry film is commonly used in the printed circuit board industry in the formation of circuitry on both inner layers and outer layers of a printed circuit board. Dry Film acts as a resist to either plating or etching chemistry. In order to understand and appreciate the current process (and how it came about) I’ll begin by explaining some of the history behind the process commonly used today. Many of the operations used by the printed circuit board industry originated (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…)

Material Allocation

Wednesday, April 27th, 2011

What does it take to build a circuit board? For starters you can’t build a printed circuit board without materials. What types of materials to be used are defined by the customer supplied documentation and or by the methods/release engineer. If requirements are not specified by the customer the methods/release engineer shall default to IPC standards. The various manufacturing operations used are a series of added and subtractive processes. All of which are determined by the methods/release engineer. It takes many different types of chemicals and materials to fabricate the printed circuit board. The most important material is what we start with and that’s the base copper clad laminate.

Base laminate is typically copper clad FR4. FR4 is a composite material consisting of (more…)

Data Preparation: Front End Engineering

Sunday, November 21st, 2010

Printed Circuit Board fabricators all have a Front End Engineering group. How the group is organized and what they are called differs from manufacturer to manufacturer. The task remains the same. They are tasked with taking in customer designs and converting them into tooling for use by the manufacturing plant to build the customer’s design. Front End Engineering of a printed circuit board manufacturer consists of at least three core disciplines… (more…)

Data Preparation: Data Formats

Sunday, December 13th, 2009

The first step in the manufacturing process of a printed circuit board is commonly referred to as data preparation. This is an operation in which information provided by the customer or designer is converted for use by the manufacturer to build the pcb. There are standard data formats required by the bare board manufacturer. The commonly accepted formats are as follows… (more…)

Generic PCB Fabrication Process

Sunday, October 4th, 2009

The steps required to build a standard printed circuit board are numerous. I shall start by itemizing the steps. I shall then document each one in greater detail as we go. The generic fabrication steps are as follows… (more…)

The Fabrication Process

Saturday, October 3rd, 2009

A misconception by many people is that printed circuit boards are a commodity. A commodity is defined as a good for which there is a demand, but which is supplied without qualitative differentiation across a market. The product is the same no matter who produces it. Paper is paper and copper is copper. One would think that if a printed circuit board is manufactured to the standards of the IPC then it would be considered as a commodity. If the board meets the specification requirements then it would be consistent enough from supplier to supplier to be considered a commodity. The reality is far different than the wish.

It is true that a printed circuit board is built to an industry standard. The industry standard specifies the minimum acceptable requirements for quality and performance. However, a board made by one manufacturer is not (more…)