Fine line printed circuit design

Quite a few printed circuit shops can manufacture a 3 mil line circuit board but only a handful can get to 1.5 mils (37 microns) and below. Yet, engineers like yourself are designing and looking for manufacturers that can resolve lines and spaces as small as .0004 inches (10 microns). The 10 micron circuit is not only possible but is presently being sold by a few shops. The proper manufacturing of fine lines is an entire package, which covers thinner laminates, small vias, smaller features with shorter interconnecting paths and special laminates to carry the traces and support the chips and only a few printed circuit manufacturers get the concept.

The evolution of fine line circuits has required the re-thinking of the whole printed circuit manufacturing concept. A board shop cannot properly etch standard ½ oz. copper to line widths less than 2 mils (50 microns) which therefore requires a new approach called differential metal plating and etching. This is used in chip manufacturing to build up the fine traces without significant etching. In fact, I have had to borrow quite a few chip technologies to get the finer lines and vias my customers required. As the circuits get smaller, usually it is required to be thinner. This means using new thinner laminates which need to retain the strength of the older, thicker laminates.

New laminate needed to manufacture the fine line circuits had to be researched with a different mind set as to its required properties. To try and find such a new unique fine line laminate, a hunt of new possible substrates was initiated. Slowly, I found different ways to make fine line circuits, using new manufacturing methods to shrink the size of the packages.

What this book will try to do is inform you, the designer, or the printed circuit manufacturing engineer, of various options available to you when you’re thinking in the future today and designing your new fine line circuit. It will educate you so when you’re talking to the printed circuit manufacturer you know a 1 mil (25 microns) line and space circuit cannot be put on a typical ½ oz. fr4 material. This book is a summary of over 2 million dollars of research and development spent by various PCB shops on my effort to lower line widths.

We will look at all aspects of a fine line circuit, giving you as many variables and options as we can. I will explain in as much detail as possible, giving away all the secret technology that I know. As many of the circuit components that make up any one fine line circuit can and do interact with each other, some of the technologies are dependent on specific combinations.