Posts Tagged ‘pcb’

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…)

Simple Yield Improvement. (Part 2)

Sunday, January 6th, 2013

In the previous post we discussed what happens to the printed circuit board structure when it is heated. We discussed how different materials expand at different rates and the effect the expansion rates have on the warp and twist of a Printed Circuit Board (PCB). We also discussed how moisture absorption can increase the degree of warp and twist and the adverse effect it has on assembly yields and potential field failures. We also discussed how dry baking removes moisture from the PCB and how it minimizes if not eliminates potential problems.

In this post we shall discuss the stabilizing effect that (more…)

Simple Yield Improvement. (Part 1)

Monday, December 31st, 2012

Over the past 15 years we have seen some very amazing advancements in technology. Our electronic devices have become smaller, faster and more powerful. The capabilities of these new devices have brought science fiction to life for many of us. What the common consumer does not realize is that these advancements have occurred in a more destructive Lead-Free assembly process. Lead Free assembly methods consisting of higher assembly temperatures (around 260ºC) for longer dwell times at temperature along with a smaller processing window for success. The assembly methods today are challenged to not only maintain yields but to improve them. All the while cutting costs where ever possible. The desire to cut cost is where we see the result of unintended consequences.

I have been asked repeatedly by customers for my opinion on methods to improve yields. I evaluate designs and work with designers and assemblers on solutions to help them improve yields. This includes in process and post process yields. In other words build it right the first time and make sure it lasts in the field. A common question I am asked by customers is…

What is the one thing that we can do that can  improve our yields?

The answer is very simple… (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…)

ITAR and Printed Circuit Boards (Part 2).

Tuesday, July 24th, 2012

In part one of this series we discussed the purpose of ITAR (International Traffic in Arms Regulations) and the government agency responsible for it’s oversight and enforcement. We also talked about what items are covered by ITAR through category 21 of the USML (United States Munitions List) and what the potential penalties are for violations. In this posting we shall talk about who ITAR applies to and the registration process.

Why do we have to register for ITAR?

Registration provides the United States Department of State necessary information used monitor and regulate defense items that are manufactured, imported and exported. It is important to point out at this point that (more…)

ITAR and Printed Circuit Boards (Part 1).

Saturday, July 21st, 2012

ITAR is an acronym for the International Traffic in Arms Regulations. The purpose of ITAR is to safeguard and control the export and import of defense related information and technology related to and that appear on the United States Munitions List (USML). ITAR is a set of regulations that came into being in order to implement provisions of the Arms Export Control Act of 1976 (AECA). The United States Department of State Directorate of Defense Trade Controls (DDTC) interprets and enforces ITAR. The mission statement of the DDTC is as follows…

The U.S. Government views the sale, export, and re-transfer of defense articles and defense services as an integral part of safeguarding U.S. national security and furthering U.S. foreign policy objectives. The Directorate of Defense Trade Controls (DDTC), in accordance with 22 U.S.C. 2778-2780 of the Arms Export Control Act (AECA) and the International Traffic in Arms Regulations (ITAR) (22 CFR Parts 120-130), is charged with controlling the export and temporary import of defense articles and defense services covered by the United States Munitions List (USML).

The USML in its entirety may be found here. The list is segregated into 21 categories. Most categories cover specific technologies, equipment or applications. The important classification that you need to be aware of is (more…)

Self-Intersecting Polygons, or is it?

Sunday, July 1st, 2012

Have you recently purchased boards from a printed circuit board factory only to find that some complex solderable features on the board that you were going to assemble to didn’t come out correctly? The data you provided to the factory was in the Extended Gerber format (RS-274-X). You notify the manufacturer so that they can determine the root cause of the error. After a few days you are told that your data was loaded into several different CAM programs by the manufacturer and the data resulted in the same shape. Some manufacturers may have even come back to you and stated that different CAM stations running different programs came up with different results, one correct and the other incorrect. Ultimately you are told that your data has illegal self-intersecting polygons that are the culprit.

In my new position at The Bare Board Group (BBG) I have the opportunity to work on a wide range of technology ranging from simple single and double sided boards to advanced rigid-flex designs with HDI blind and buried vias. Its safe to say that we see it all since we are capable of providing boards to meet most design criteria. That being said we also came across the infamous self-intersecting polygon non-conformance on a board we provided. I have decades of experience working with the Gerber format and programming in general. I also like to understand how a problem occurs so that I can prevent it from happening again in the future. I started evaluating the non-conformance and was very surprised by what I discovered at the end of my investigation. To understand the non-conformance and the root cause of the problem you shall first need (more…)

The Bare Board Group Incorporated.

Sunday, June 24th, 2012

I joined the Bare Board Group (BBG) in March of 2012 as the Engineering Director of the organization. BBG began operations in 2002 in response to a growing need among smaller OEM and EMS companies for lower volumes of printed circuit boards at lower offshore prices. BBG became a US supplier of printed circuit boards built in the Far East. BBG set out to eliminate the fears and difficulties of offshore manufacturing by becoming an extension of its customers’ purchasing departments, handling all interactions with pre-qualified overseas vendors.

During my time at the company I have come to appreciate the differences that set BBG apart from their counter-parts sourcing boards from other parts of the Globe. The key differences are as follows… (more…)

Shelf Life Identification of a PCB.

Saturday, November 5th, 2011

How does one identify the shelf life of a printed circuit board?

By convention the printed circuit board fabricator shall mark the printed circuit board with a four digit date code. The date code consists of a two digit week number ranging from 01 (the 1st week in January) to 52 (the last week in December). The year code would be 99 for the year 1999 or 01 for the year 2001. Commercial fabricators use a week/year format. Date code 0199 would be the first week of January of 1999. Military fabricators use a year/week format. Date code 0152 would be the last week of December of 2001. The printed circuit board fabricator shall place the date code on what is traditionally referred to as the circuit side of the printed circuit board.

What is the circuit side of a pcb?

To understand the term circuit side, you need to learn a little history of the printed circuit board industry. In the beginning (more…)

Shelf Life = Solderability = Supply Chain Management

Saturday, June 25th, 2011

I had an interesting conversation with a colleague the other day. They wanted to return some printed circuit boards to an off-shore manufacturer because not all of the surface mount pads would solder. I help friends and customers troubleshoot problems all the time. Its just good business.

“Was it the entire lot of boards or only a few?”, I asked.

“Well, when we soldered the first batch the pads wet with solder with no problem. The second batch from the same lot has solderability issues. The pads don’t wet properly. I can’t explain it but nothing has changed here. The boards have ENIG on them so it must be the boards.”

“Well, if the first batch soldered and the second batch from the same lot didn’t then there’s a problem. How much time has passed between batches?”

“Hmmmm. About three years”

“ouch”

We then proceeded to have a conversation about shelf life. This is a topic that I find many people don’t know about or understand properly. Put simply, (more…)