-
- News
- Books
Featured Books
- smt007 Magazine
Latest Issues
Current IssueDo You Have X-ray Vision?
Has X-ray’s time finally come in electronics manufacturing? Join us in this issue of SMT007 Magazine, where we answer this question and others to bring more efficiency to your bottom line.
IPC APEX EXPO 2025: A Preview
It’s that time again. If you’re going to Anaheim for IPC APEX EXPO 2025, we’ll see you there. In the meantime, consider this issue of SMT007 Magazine to be your golden ticket to planning the show.
Technical Resources
Key industry organizations–all with knowledge sharing as a part of their mission–share their technical repositories in this issue of SMT007 Magazine. Where can you find information critical to your work? Odds are, right here.
- Articles
- Columns
Search Console
- Links
- Media kit
||| MENU - smt007 Magazine
Stop Over-specifying Your Materials
May 25, 2023 | I-Connect007 Editorial TeamEstimated reading time: 3 minutes

Columnist Kelly Dack has had a pretty wide range of experiences. As a PCB designer, he has sat behind the desk at an NPI company, an OEM, a fabricator, and now an EMS provider. We asked him to share a few thoughts on the materials selection process and how it could be improved.
Kelly also explains how overly zealous PCB designers make things too complicated by over-specifying their materials, which leads to confusion once the board goes to volume production overseas. Are you over-constraining your material choices?
Andy Shaughnessy: Kelly, what is your process for material selection? Walk us through it.
Kelly Dack: Sure. I actually wrote a guideline for our customers that explains the material selection process. As mentioned, over-specification in the EMS realm is rampant and problematic from the standpoint of scaling products to volume overseas. This guide has a section on laminated materials that includes a simple, tried-and-true material specification. It says, “Materials: laminated glass epoxy resin type FR-4 series or equivalent per IPC-4101 with a Tg of greater than or equal to xxx.” This is a number that we can modify. We say, for instance, 170°C, and a Td (time to delamination) temperature of greater than 3XX°C. Those are all movable numbers that designers can edit.
That’s how we specify our laminate materials for printed circuit boards, unless the performance criteria dictates that it needs to go further and get more specific—for example, high-performance signal integrity constraints, impedance control, or exotic materials. But otherwise, FR-4 laminates cover 85–95% of our customers’ design requirements.
Shaughnessy: Where do designers typically go to find this information? What documents or guidelines should they use?
Dack: Many designers use their company’s documentation template or go to their elders and learn through knowledge that has been passed down. I just went through a bunch of our customers’ designs and fabrication drawings, and I found plenty of examples of customer material specification. Many of them call out a specific IPC-4101 slash number, and it’s usually the same slash number each time. It’s either 4101/26 or /21.
Shaughnessy: IPC has said that slash sheets were not ever meant for designers to use; they’re mainly a way for PCB supplier purchasing and marketing departments to communicate with buyers.
Dack: I’m glad to hear that confirmation as it was my understanding as well. This all came from the MIL-S-13949 spec back in the mil-spec days, most of which has been replaced by IPC standards. But we are seeing some of our customers’ designs specifying laminates by using slash numbers and I get the feeling it’s just because of tribal knowledge. If you look at most of the designs, they appear to be basic, not really requiring a specific material. The board would work fine with a generic glass-epoxy laminate because it has no impedance control or performance criteria. We just print and etch some copper onto it, create a circuit, and it moves electrons.
It’s usually only when we get into the super high-speed design in the gigahertz range where we have to start thinking about loss tangents and permittivities. Here’s the challenge: How much do you constrain? If you’re building your PCB design down at the local prototype shop, which will build a board any way you want, everybody seems fat and happy. But when you want to build 1 million boards, you must introduce a low-cost constraint because you can’t pay $1,000 a board and make a profit. You scale to volume to get cost savings. To realize maximum cost savings, this has always been done offshore. But designers must realize that offshore suppliers don’t have access to all the materials and capabilities that U.S. prototype companies have. Over-specification of laminate materials by composition, performance characteristics, or a trademarked source creates a terrible, but avoidable ordering situation, putting quotes on hold every single day. The simple fact is that it causes our offshore PCB suppliers to request and obtain approval for material substitutions before they can proceed.
To read this entire conversation, which appeared in the May 2023 issue of Design007 Magazine, click here.
Suggested Items
Real Time with... IPC APEX EXPO 2025: Tariffs and Supply Chains in U.S. Electronics Manufacturing
04/01/2025 | Real Time with...IPC APEX EXPOChris Mitchell, VP of Global Government Relations for IPC, discusses IPC's concerns about tariffs on copper and their impact on U.S. electronics manufacturing. He emphasizes the complexity of supply chains and the need for policymakers to understand their effects.
The Chemical Connection: Surface Finishes for PCBs
03/31/2025 | Don Ball -- Column: The Chemical ConnectionWriting about surface finishes brings a feeling of nostalgia. You see, one of my first jobs in the industry was providing technical support for surface cleaning processes and finishes to enhance dry film adhesion to copper surfaces. I’d like to take this opportunity to revisit the basics, indulge in my nostalgia, and perhaps provide some insight into why we do things the way we do them in the here and now.
NUS Physicists Discover a Copper-free High-temperature Superconducting Oxide
03/28/2025 | PRNewswireProfessor Ariando and Dr Stephen Lin Er Chow from the National University of Singapore (NUS) Department of Physics have designed and synthesised a groundbreaking new material—a copper-free superconducting oxide—capable of superconducting at approximately 40 Kelvin (K), or about minus 233 degrees Celsius (deg C), under ambient pressure.
AT&S Sets New Standards in the Recycling of Copper and Chemicals
03/25/2025 | AT&SAT&S has been working for years to reduce the ecological footprint of its production sites worldwide with a comprehensive sustainability strategy and considerable investments.
Empowering the Future of Advanced Computing and Connectivity: DuPont Unveils Innovative Advanced Circuit Materials in Shanghai
03/24/2025 | DuPontDuPont will showcase how we are shaping the next generation of electronics at the International Electronic Circuits (Shanghai) Exhibition 2025.