Archive for January, 2009

Why can’t I use FR4 with Lead Free Soldering.

Saturday, January 17th, 2009

You can build a printed circuit board and solder it through a lead free soldering temperatures. It is not advisable! I know some designers that use standard FR4 for lead free soldering applications. The designs are simple single and double sided boards. The companies that they work for have done the due diligence to prove out their design and manufacturing process. On moderate to complex designs they specify lead free soldering compliant laminates in place of FR4. The compliant laminates are much more expensive than standard FR4. They made the upfront investment system by doing the testing and evaluating to save money down the road. They know what they can get away with and have the test data to prove it. However, the results are specific to their designs and their assembly process. When in doubt, play it safe and specify lead free soldering compliant laminate. In order to justify the cost of the more expensive laminate you need to understand what happens to the material at high temperatures.

The main challenge faced by a laminate system is (more…)

RoHS vs. Lead Free Assembly

Saturday, January 17th, 2009

It is easy to mis-interpret the relationship between RoHS and Lead Free Assembly. Lead Free Assembly has been around for decades in limited applications. RoHS came about when the European Union passed a directive known as WEEE. WEEE or Waste of Electrical and Electronic Equipment (2002/96/EWG) regulates the end of life disposal and recycling of electrical waste. The legislation states that producers are responsible for waste and financing its collection. Users from private households should be allowed to recycle products free of charge. To reduce recycling costs the restricted or banned materials, manufacturers are striving to remove these substances from their product. This is where RoHS comes in.

RoHS or Restriction of Hazardous Substances (2002/95/EWG) prohibits the use of the following substances: (more…)

Example Fabrication Drawing (Part 2)

Sunday, January 11th, 2009

Automated assembly equipment typically requires that the board being assembled move along a track. The actual board sits on two chains on either side of the track. As the chain moves along the assembly line the board is moved along with it from station to station. If components are close to the board edge they may interfere with how the board sits on the chain. Hence the need for rails.

Rails are extensions of the pcb that are attached and later removed after the board is assembled. Rails are added for handling purposes and to provide clearance for components that may be close to the board edge.  It is common practice for anyone that assembles printed circuit boards with components to (more…)

Example Fabrication Drawing (Part 1)

Wednesday, January 7th, 2009

There is an old saying, “A picture speaks a thousand words.” To help understand what a fabrication drawing is, I have posted several views along with brief explanations. The first view is a full size view of a fabrication drawing (more…)

Sample fabrication drawing notes.

Monday, January 5th, 2009

In this post I shall provide a listing of sample fabrication drawing notes that may be used on any fabrication drawing for a pcb. Fabrication drawing notes typically specify materials and finished requirements in a text outline form. Critical requirements shall be specified in the note structure.

Notes: (more…)

What is a Fabrication Drawing?

Sunday, January 4th, 2009

Not clearly specifying information may result in errors along the manufacturing supply chain. For example, one of my customers had an old legacy design they needed to have built. The fabrication drawing called for FR4 as the material the board was to be built on. The original designer specified a high volume resistivity requirement in an email sent to the previous manufacturer. The requirement was never added to the the fabrication drawing. The company that used to build the pcb went out of business. The original designer retired. My company built the design. A contract manufacturer assembled the boards. The customer installed it into their rack. None of the assemblies worked.

To make a long story short, (more…)