-
- News
- Books
Featured Books
- design007 Magazine
Latest Issues
Current IssueLevel Up Your Design Skills
This month, our contributors discuss the PCB design classes available at IPC APEX EXPO 2024. As they explain, these courses cover everything from the basics of design through avoiding over-constraining high-speed boards, and so much more!
Opportunities and Challenges
In this issue, our expert contributors discuss the many opportunities and challenges in the PCB design community, and what can be done to grow the numbers of PCB designers—and design instructors.
Embedded Design Techniques
Our expert contributors provide the knowledge this month that designers need to be aware of to make intelligent, educated decisions about embedded design. Many design and manufacturing hurdles can trip up designers who are new to this technology.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - design007 Magazine
Slash Sheets: Don’t Fall Into the Trap
June 8, 2023 | Geoffrey Hazelett, Technical SalesEstimated reading time: 2 minutes
Slash sheets can be confusing, and this is a big topic, so let’s start big and drill down from there.
Here’s the big picture regarding slash sheet references: They were designed to provide handy groupings of PCB materials (laminates, polyimides, etc.) that go into a stackup. These groupings are designed around mechanical characteristics to provide insight for PCB fabricators to identify similar laminates with similar properties.
These documents were not designed to be used by PCB designers to help select the correct material for their job. For high-speed designers in particular, these group references can be a trap. While two material families may have similar mechanical processing characteristics for fabricators, the materials can have wildly dissimilar electrical characteristics. Dielectric constant (Dk), dissipation factor (Df), copper roughness values, and glass weave styles (106/1080/3313, etc.) are all significant for signal integrity and are not appropriately distinguished within slash sheets.
For example, due to this ambiguity of electrically significant values, two electrically dissimilar performing materials could be substituted for one another. The two materials may have similar processing temperatures and roughly similar characteristics; to savvy PCB designers with an eye for signal integrity, slash sheets fall short.
For example, IPC-4101/126 has a maximum Dk value of 5.4, and a Df of 0.035. To use Isola materials as an example, this lumps 185HR, 370HR, IS550H, IS415, FR408HR, and I-Speed all together. So, if a designer needed high-frequency performance with something like I-Speed, but allowed a substitution with /126, their fabricator would likely swap the material to something else. That other material could likely be a 185HR or 370HR, which have significantly differing Dk/Df values as well as differing glass weave types.
A designer who wants to control the materials in their stackup is often pressed to communicate specific acceptable alternative supplier laminates, such as “Panasonic Megtron 6 (or Isola I-Speed),” to their fabricator.
To use shoes as an analogy: Shoes generally all have a sole, laces, breathable top, etc. A slash sheet reference would help identify “shoes,” but doesn’t help identify “running shoes” vs. "hiking boots." Nike and Adidas both make running shoes, so a designer could use “/shoes” (slash sheet reference), but they may be in trouble if they are running a marathon and want “Nike or Adidas running shoes.” A limitation of the slash sheets is that there are significant differences between the brands and the types of shoes, and unfortunately they could all be lumped together in the same slash sheet for “shoes.”
A designer should clearly communicate with the fabricator regarding the desired glass weave, resin type, etc., going into their board if they wish to ensure their signal integrity characteristics will be met. Don’t take unnecessary short cuts when a few more words can save a world of headache.
Geoffrey Hazelett has a bachelor of science degree in electrical engineering, and was vice president of sales at Polar Instruments for several years. He is currently home with his new baby daughter, Sage.
This article originally appeared in the May 2023 issue of Design007 Magazine.
Suggested Items
The Chemical Connection: Reducing Etch System Water Usage, Part 2
05/02/2024 | Don Ball -- Column: The Chemical ConnectionIn my last column, I reviewed some relatively simple ways to reduce water usage in existing etch systems: cutting down cooling coil water flow, adding chillers to replace plant water for cooling, lowering flow rate nozzles for rinses, etc. This month, I’ll continue with more ways to control water usage in your etcher. Most of these are not easily retrofittable to existing equipment but should be given serious consideration when new equipment is contemplated. With the right combination of add-ons, it is possible to bring the amount of water used in an etch system to almost zero.
Designer’s Notebook: What Designers Need to Know About Manufacturing, Part 2
04/24/2024 | Vern Solberg -- Column: Designer's NotebookThe printed circuit board (PCB) is the primary base element for providing the interconnect platform for mounting and electrically joining electronic components. When assessing PCB design complexity, first consider the component area and board area ratio. If the surface area for the component interface is restricted, it may justify adopting multilayer or multilayer sequential buildup (SBU) PCB fabrication to enable a more efficient sub-surface circuit interconnect.
Insulectro’s 'Storekeepers' Extend Their Welcome to Technology Village at IPC APEX EXPO
04/03/2024 | InsulectroInsulectro, the largest distributor of materials for use in the manufacture of PCBs and printed electronics, welcomes attendees to its TECHNOLOGY VILLAGE during this year’s IPC APEX EXPO at the Anaheim Convention Center, April 9-11, 2024.
ENNOVI Introduces a New Flexible Circuit Production Process for Low Voltage Connectivity in EV Battery Cell Contacting Systems
04/03/2024 | PRNewswireENNOVI, a mobility electrification solutions partner, introduces a more advanced and sustainable way of producing flexible circuits for low voltage signals in electric vehicle (EV) battery cell contacting systems.
Heavy Copper PCBs: Bridging the Gap Between Design and Fabrication, Part 1
04/01/2024 | Yash Sutariya, Saturn Electronics ServicesThey call me Sparky. This is due to my talent for getting shocked by a variety of voltages and because I cannot seem to keep my hands out of power control cabinets. While I do not have the time to throw the knife switch to the off position, that doesn’t stop me from sticking screwdrivers into the fuse boxes. In all honesty, I’m lucky to be alive. Fortunately, I also have a talent for building high-voltage heavy copper circuit boards. Since this is where I spend most of my time, I can guide you through some potential design for manufacturability (DFM) hazards you may encounter with heavy copper design.