At the conclusion of our webinar, PCB Manufacturing Facilities: Certifications, Compliance, and Security - we had several questions submitted to our presenter, Ed McMahon, CEO at Epec. We have compiled these questions into a readable format on our blog.
Q&A From Our Live PCB Webinar
- Should I list the specific material that I want my PCB to be made on or use the IPC slash number?
- How do I inspect the cross section when I have the PCB factory sent it to me?
- What is a coupon?
- Why is the IPC-4101 slash sheet not included in the Certificate of Conformity? For example, IPC-4101/126.
- Our PCB fab drawing calls for IPC-4101/126 and a maximum Dk of 4.1. Does Epec use a material that meets IPC-4101/126 and meets a Dk of 4.1? I ask this because IPC-4101/126 allows for a Dk greater than 4.1.
Watch the Recording Below:
Question: Should I list the specific material that I want my PCB to be made on or use the IPC slash number?
Answer: That’s a very good question. And there's pros and cons to both. If you say, listen, I want my material to be 370 HR, that's great because now you know specifically that you're going to get that 370 HR every single time. You don't have to worry about any changes in performance. So, that's great. The downside to that is, is that if 370 HR have trouble getting it, I can't substitute. So, that's one of the challenges if you specify a specific laminate, is that at that point, I cannot go to a different product based upon, you know, what somebody else may have that is very similar because we have to do that.
Question: How do I inspect the cross section when I have the PCB factory sent it to me?
Answer: Well, traditionally, the way that we do it, and all those pictures that you saw are with a microscope with a camera. However, there are companies out there that will take a print circuit board from any factory and will do cross sections for you, and you can pay them to do it. And they're third-party labs, and they'll do a section, they'll even do thermal cycling on a printed circuit board. And you can identify, and you can show them exactly where you want these tests to be done, right? And again, we talk about a thermal shot, right? A lot of you take bare boards, order extras many times and go ahead and, you know, put them under extreme heat and you'll find things like voids.
You'll find things like delamination; you'll find things like the pads coming off. If you submit those parts to extreme heat, you'll find that you're going to find out if there's problems. And the higher the layer count, the more complex the board, the more you want to do that type of analysis, right? Because if you look at that printed circuit board that's in the middle of this slide right here, this one's a 16 layer, I want to say, there's something like 13,000 holes in that part. And there's a lot of opportunities. It's got blind and buried vias. It's got, it's got plated shut holes. There's lots of opportunities to have challenges. So, if you submit that board to thermal stress, you're going to find out if, in fact, it's going to pass what you need to pass. Just like we do and in many instances, we used to do more of what we were doing at a hotter level.
Question: What is a coupon?
Answer: A coupon or test coupon on a printed circuit board (PCB) production panel is used to test the quality of the fabrication process. Test coupons are fabricated on the same panel as the PCBs, typically at the edges and are then inspected to ensure proper layer alignment, electrical connectivity, and cross sectioned to inspect internal structures. Coupons can be designed custom for a PCB or selected from a library (i.e. – MIL spec has a specific coupon that must be used) and they are used to verify the consistency of plating, etching, and lamination across the whole panel.
Question: Why is the IPC-4101 slash sheet not included in the Certificate of Conformity? For example, IPC-4101/126.
Answer: Per our ISO procedures, the certificate of conformance that we provide indicates that we are in conformance with all of the specifications on your drawing. However, if you wanted that sheet included it is certainly possible however, and based upon your next question, it is probably more useful if the data sheet of the actual material used was added instead.
Question: Our PCB fab drawing calls for IPC-4101/126 and a maximum Dk of 4.1. Does Epec use a material that meets IPC-4101/126 and meets a Dk of 4.1? I ask this because IPC-4101/126 allows for a Dk greater than 4.1.
Answer: In this case where you list both, we will take both requirements into consideration when choosing a laminate for your material. The thing to keep in mind when specifying Dk is to include the frequency at which you want the maximum value as most data sheets have it listed from 10Ghz to 100Mhz.