Elementary, Mr. Watson: Rules of Thumb—Guidelines vs. Principles for PCB Design
Beyond Design: High-speed Rules of Thumb
Global PCB Connections: A Technical Overview of Long-flex Printed Circuit Boards
The Bare (Board) Truth: The Top 10 Ways Designers Can Increase Profits
April 21, 2016 | Mark Thompson, Prototron CircuitsEstimated reading time: 2 minutes
Some of you are probably wondering about the title of this article. “What could Mark possibly mean? How can a lowly PCB designer like me increase our company’s profits?”
So, can you truly increase profitability through PCB design practices? Yes, you can. And it starts with a philosophy that embraces DFM techniques. Then you must be ready for the initial release to a fabricator by ensuring that you are communicating all of your specifications and needs clearly to the fabrication house so that you get an accurate quote.
Let’s dive in, starting with Number 10 and working our way to the most important way a designer can increase company profits.
10. Accurate Fab Notes
I cannot over-stress this one. Lets talk about some common fab notes that can cause confusion, sometimes delaying your quote.
For instance, do copper weights refer to starting or finished weight? A standard note may read, “All copper weights listed on the stack-up detail are finished weights.” But a glance at the provided stack-up shows both 1 oz. inners and outers.
Remember, the first fab note specified FINISHED weights. This is not a problem for an internal layer, as they are “print and etch” for the most part. Their desired copper features are protected by the photosensitive resist and are simply printed, developed (to remove the resist not hardened by the light source), etched (to remove the unwanted metal) and resist stripped to remove the resist covering your desired copper features. So a 1 oz. callout for an inner layer is not at all uncommon.
The 1 oz. finish for the outer layers, however, is a bit unusual, given the fact that IPC recommends a minimum of 8/10 of a mil of plated copper on the surface and in the barrel of the hole for continuity. So starting on .5 oz. or even .25 oz. copper foils would mean we would have to plate less than what IPC recommends to finish at 1 oz.
The reality is that most fabricators err towards a full ounce or 1.4 mils of plating in the barrel and on the surface to meet that IPC minimum. That means starting on .25 oz. copper foil on the outers and plating up a full ounce results in 1.25 oz finish, which does not meet the drawing callout of 1 oz finished.
Worse yet, there may be impedance calculations that the customer has based on the 1 oz. finish for outer layers. Increasing the finished copper weight may mean a REDUCTION in your impedance lines. If you have already taken them down to .003” for instance, this may be a problem for the manufacturer.
This clarification about what is needed for desired copper can take additional time at the quote process. I am happy to say we are seeing more and more customers, both old and new, embracing this and creating non-conflicting manufacturing notes that allow for a 1 oz. additional plate.
To read this entire article, which appeared in the March issue of The PCB Design Magazine, click here.
Share on:
Suggested Items
Unlocking Advanced Circuitry Through Liquid Metal Ink
10/31/2024 | I-Connect007 Editorial TeamPCB UHDI technologist John Johnson of American Standard Circuits discusses the evolving landscape of electronics manufacturing and the critical role of innovation, specifically liquid metal ink technology, as an alternate process to traditional metallization in PCB fabrication to achieve ever finer features and tighter tolerances. The discussion highlights the benefits of reliability, efficiency, and yields as a tradeoff to any increased cost to run the process. As this technology becomes better understood and accepted, even sought out by customers and designers, John says there is a move toward mainstream incorporation.
Fresh PCB Concepts: The Critical Nature of Copper Thickness on PCBs
10/31/2024 | Team NCAB -- Column: Fresh PCB ConceptsPCBs are the backbone of modern electronics and the copper layers within these boards serve as the primary pathways for electrical signals. When designing and manufacturing PCBs, copper thickness is one of the most critical factors and significantly affects the board’s performance and durability. The IPC-6012F specification, the industry standard for the performance and qualification of rigid PCBs, sets clear guidelines on copper thickness to ensure reliability in different environments and applications.
Book Excerpt: The Printed Circuit Designer’s Guide to... DFM Essentials, Ch. 1
10/25/2024 | I-Connect007The guidelines offered in this book are based on both ASC recommendations and IPC standards with the understanding that some may require adjustment based on the material set, fabricator processes, and other design constraints. This chapter details high-frequency materials, copper foil types, metal core PCBs, and the benefits of embedded capacitance and resistor materials in multilayer PCBs.
The Cost-Benefit Analysis of Direct Metallization
10/21/2024 | Carmichael Gugliotti, MacDermid AlphaCarmichael Gugliotti of MacDermid Alpha discusses the innovative realm of direct metallization technology, its numerous applications, and significant advantages over traditional processes. Carmichael offers an in-depth look at how direct metallization, through developments such as Blackhole and Shadow, is revolutionizing PCB manufacturing by enhancing efficiency, sustainability, and cost-effectiveness. From its origins in the 1980s to its application in cutting-edge, high-density interconnects and its pivotal role in sustainability, this discussion sheds light on how direct metallization shapes the future of PCB manufacturing across various industries, including automotive, consumer electronics, and beyond.
Connect the Dots: Designing for Reality—Pattern Plating
10/16/2024 | Matt Stevenson -- Column: Connect the DotsIn the previous episode of I-Connect007’s On the Line with… podcast, we painted the picture of the outer layer imaging process. Now we are ready for pattern plating, where fabrication can get tricky. The board is now ready to receive the copper traces, pads, and other elements specified in the original CAD design. This article will lay out the pattern plating process and discuss constraints in the chemistries that must be properly managed to meet the customer's exacting manufacturing tolerances.