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What do you prefer for a final solderable finish on your printed circuit boards?

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Shelf Life Identification of a PCB.

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 Read the rest of this entry »

Blog Updates.

September 1st, 2011

I thought I would take a few minutes to clarify and highlight a few recent changes that I’ve made to the site.

  1. I’ve added a site plugin named WPtouch that makes pcbdesignschool.com mobile device friendly. I’ve tried to use my Droid smart phone to show friends my content. I’ll be the first to admit that its a slow painful process waiting for the content to load. WPtouch reformats the blog so that mobile device users may enjoy the content quickly on the go. When you visit the site from a standard personal computer you can view the site normally. When you use a mobile device you automatically view the site in the mobile device friendly format.
  2. We now have a polling plugin named WP-Polls that we use to ask a question of our visitors. The polls are pcb industry related. These are non-scientific polls and the results are available to anyone that wants to see them. We don’t capture, store or share anyone’s personal information. Its an opportunity to see what other people in the industry are thinking. Read the rest of this entry »

What damage does the assembly process do to a pcb? (part 6)

August 31st, 2011

In this final planned post of the “What damage does the assembly process do to a pcb?” series we shall discuss copper diffusion.

What is copper diffusion?

When soldering, copper diffusion is a process in which copper atoms are removed from the copper surface and redistributed into the solder over a wide area.

Back in 2005 I was running some thermal and solderability tests on multilayer boards using various types of cured laminates, different surface finishes and various solder alloys. I was doing my RoHS and Lead-Free due diligence. I had a whole range of tests that I was running. One test consisted of solder dipping a test board in 288°C solder for 20 – 5 second intervals. I was trying to make a multilayer board built on phenolic laminate delaminate. When I reached the tenth dip I had to stop my test. I didn’t make the board delaminate but I did dissolve away much of the copper circuitry into the solder pot. Read the rest of this entry »


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