Fresh PCB Concepts: Everything Your PCB Supplier Needs Upfront for Quoting
Target Condition: Life in the Engineering Ecosystem
Abe: With Megtron 7 the loss is maybe 20-30% improved from the Megtron 6.
Starkey: Can I just ask, going away from the performance characteristics and the enabling characteristics, but speaking as a fabricator, does it present any problems in fabrication, or any particular special precautions needed?
Senese: Let’s address this by going through our targets for Megtron 7, which include the product characteristics, but also the kinds of things you're talking about. We know from experience that even products that have very good characteristics are unsuccessful if they don't fit into a certain window in terms of how the fabricators can use them.
Abe: Okay, our first target is of course the DF/DK properties. It's most important for us. Our goal was half of the loss of Megtron 6. That's our most important target. Then Megtron 6 is, electrically, very high end, but it also has a very good thermal and reliability performance, so Megtron 7 should be the same. So that is our second target.
Starkey: If I patiently fabricate and I have established a process procedure for building boards with Megtron 6, can I just use that established procedure for building boards on Megtron 7?
Abe: Yes, it’s very close.
Senese:One of the things that Megtron 6 has that is unique compared to previous materials that have been used in high-speed, beyond just better electrical performance, is the rheology of the system that allows material to be laminated in a way where the dielectrics are very consistent across any panel size. That means if somebody has to back drill for getting rid of stubs, they can do it very consistently with Megtron 6. A lot of the designs for the back planes and daughter cards that are being used now exploited that property because the thickness of the edge, the center, and from board-to-board was so consistent that they could easily set up to maintain a very tight back-drilling to get the stubs on any layer within 2–3 mils of the next interconnect, which is very tight.
That was something that, when Megtron 6 was designed, nobody planned on, but it has become a de facto standard. Luckily for Panasonic, other materials that look good on paper didn't always succeed in the market because that was something that had been exploited by the fabricators. So this is something that was added to our list of the things we have to do ,because we're designing this material to replace Megtron 6, and if they can't do this with this material, our own material will fail.
Starkey: Exactly.
Senese: So that's one thing that's similar with Megtron 7, the lamination cycle, the lamination thickness consistency, and the ability to exploit that, to make those designs is still there. One of the things that most of these high-end materials have in common, especially the thermally robust ones, is that drill wear is always a question. Some materials in the past have actually just failed because the drill wear went from a product like Megtron 6 where you could do a thousand hits on almost any size, down to sub-500 hit level. The drills for these materials, as you can imagine when you have a board that's almost half an inch thick, are very expensive. Another thing that happened is that people said, "Well, does it drill okay? Is it as good at least as Megtron 6?" Actually, in the wear studies that we've done with Megtron 7, it is a little better than Megtron 6.
Starkey: What sort of foils are you using or are recommended for use with the materials? What sort of bonding treatments for the foils, with signal integrity in the lines?
Page 2 of 3
