Latest / Hardware Startups with Fexingo: Devices, Robotics, and Manufacturing Tech Companies / How Hardware Startups Use Laser Direct Structuring for 3D Antennas
Transcript
- Lucas: If these conversations are useful for what you're building or running, we're glad you're here. Today we're talking about a manufacturing technique that lets you embed an antenna directly into the plastic housing of a device — no separate module, no flex cable, no adhesive. Luna: Laser direct structuring. LDS. I've seen it in a few teardowns but never really understood how a startup would actually use it. Lucas: Yeah, and honestly, if today was worth a coffee to you, that's the link — buy me a coffee dot com slash fexingo. Listeners like you are why this show stays ad-free. Luna: It's a small thing that makes a big difference for us. Appreciate it. Lucas: So LDS — it starts with a special polymer, usually a polyamide or liquid crystal polymer mixed with a metal additive. You injection mold your part just like normal, then a laser draws the antenna pattern onto the surface. Luna: And the laser activates the additive so it can be plated? Lucas: Exactly. The laser ablates the surface and exposes the metal compound, creating a micro-rough track. Then the part goes into an electroless copper bath — copper deposits only on those laser-activated lines. You can build up multiple layers: copper, then nickel, then a gold flash for corrosion resistance. Luna: So you end up with a 3D circuit trace right on the inside of your enclosure. That's huge for space-constrained devices. Lucas: It is. And it's not just antennas — you can also integrate sensors, touch interfaces, even shielding. But the killer app for hardware startups is wireless connectivity: Bluetooth, Wi-Fi, LoRa, cellular IoT. I talked to a smart-lock startup last year that was struggling with antenna placement inside a metal-reinforced door handle. Luna: Right, because a typical chip antenna or a stamped-metal antenna takes up board space and has clearance requirements. If your enclosure is tight, you're stuck. Lucas: They were using a flex antenna adhered to the inside of the plastic, but the flex cable kept detaching during drop testing. And the assembly was manual — a person had to peel and stick it. With LDS, they redesigned the handle housing to have the antenna trace molded into the inner surface. No extra part, no adhesive, no cable. Luna: What kind of cost impact did they see? Lucas: The tooling for the lds grade plastic is about 20 percent more expensive than standard ABS — but the per-part cost delta is small, maybe ten to fifteen cents. When you factor in eliminating the antenna module, the flex cable, and the manual assembly labor, their total unit cost dropped by about 40 cents. On a hundred thousand unit run, that's forty thousand dollars. Plus the yield improved because there's one less manual step. Luna: Forty thousand dollars — that's meaningful for a startup. But you need volume to justify the tooling investment. Lucas: Yeah, LDS tooling typically runs ten to twenty thousand dollars more, depending on complexity. So if you're only making a thousand units, that premium is ten to twenty dollars per unit — probably not worth it. The breakeven point is usually around ten to fifteen thousand units, assuming you're replacing a three-dollar antenna assembly. Luna: So for a Kickstarter campaign that sells a few thousand, you'd stick with a chip antenna or a flex. But if you're scaling to production runs of tens of thousands, LDS starts to make sense. Lucas: Exactly. And there are other benefits beyond cost. RF performance is often better because you can optimize the antenna geometry for the exact shape of your enclosure. You can make it longer for better efficiency, or shape it to avoid interference from metal components inside the device. Luna: I've read that LDS antennas can have up to 30 percent better efficiency compared to a chip antenna of the same size. Is that your experience? Lucas: It depends on the design, but yes, I've seen similar numbers. The key is that the trace can be wider and thicker than a PCB trace — you're not limited by the copper thickness on a standard board. And you can put it on a curved surface, which gives you more length in a small footprint. Luna: What about design constraints? I imagine you can't just draw any shape. Lucas: There are guidelines. Minimum line width is usually around 100 microns, and spacing between lines should be at least 100 microns as well. The laser can do finer, but plating uniformity suffers. Also, the trace can't cross sharp corners — you need fillets, otherwise the copper can crack during thermal cycling. And you have to avoid areas that will be under high mechanical stress, like snap-fit features. Luna: So you need to design the plastic part with the antenna trace in mind from the start. You can't just take an existing enclosure and add LDS later. Lucas: Right. It's a co-design exercise. The mechanical engineer and the RF engineer have to collaborate early. That's a cultural challenge for startups that are used to iterating quickly with off-the-shelf antennas. But the payoff is a more integrated, more reliable product. Luna: Are there any gotchas with the LDS material itself? I've heard some grades absorb moisture and can affect RF performance. Lucas: That's true. The most common LDS materials are polyamide-based, and they can absorb up to 2 percent moisture by weight. That shifts the dielectric constant, which detunes the antenna. So you need to either use a low-moisture-absorption grade, like LCP — liquid crystal polymer — or design the antenna to be tolerant of a range of dielectric constants. Most experienced LDS suppliers will help you characterize that. Luna: And what about the plating process? Is it something a startup can do in-house? Lucas: Not realistically. Electroless plating requires chemical baths, waste treatment, and process control. It's a specialized operation. But there are plenty of contract manufacturers that offer LDS as a service. You send them your injection-molded parts, they laser and plate them, and send them back. Typical lead time is two to three weeks. Luna: So the startup molds the part, ships it to the LDS house, then gets it back for final assembly. That adds a logistics step. Lucas: It does, but it's manageable. And some injection molders have in-house LDS capabilities. If you're doing high volume, that's the ideal scenario — you mold, laser, plate, and ship all in one facility. Luna: What about testing? How do you verify the antenna performance before you commit to tooling? Lucas: You can prototype with laser-structured parts without production tooling. Some LDS service providers offer low-volume laser structuring on 3D-printed parts made from lds compatible resin. That lets you test the antenna pattern functionally. You can also simulate the antenna in software using the material properties of the LDS plastic. But ultimately, you'll want to do a real-world range test with a few prototype units. Luna: I've also seen LDS used for something called '3D meander antennas' — basically a zigzag trace that fits in a small space. Is that common? Lucas: Very common for Bluetooth and Wi-Fi. A quarter-wave antenna at 2.4 GHz is about 30 millimeters long. If you meander it, you can fit that into a space that's maybe 15 by 5 millimeters. LDS lets you put that meander on a curved wall of the enclosure, so it doesn't take up any flat surface area. Luna: So you could put the antenna on the inside of a cylindrical smart-home device, like a smoke detector or a light bulb? Lucas: Exactly. I saw a smart-bulb startup that put an LDS antenna on the inside of the plastic dome. The bulb had a metal heatsink that would have blocked a traditional antenna, but by placing the trace on the dome, they got excellent signal strength. And they didn't have to add any extra components. Luna: Are there any industries where LDS is becoming a standard practice, like automotive or medical? Lucas: Automotive has been using LDS for years — key fobs, tire pressure sensors, GPS antennas. The vibration and temperature cycling resistance is excellent. Medical devices use it for disposable sensors and implantable antennas where reliability is critical. For hardware startups, the trend is toward more integration, so I expect LDS to become more common as tooling costs come down. Luna: And the tooling cost is coming down? Lucas: Slowly. The laser systems themselves are getting cheaper — a desktop LDS system from a company like LPKF now costs around a hundred thousand dollars, which is affordable for a contract manufacturer. But the mold tooling premium is driven by the need for higher mold temperatures and specialized steel to handle the abrasive LDS material. That part isn't dropping much. Luna: So if I'm a startup building a connected device, what's the first step to evaluate LDS? Lucas: First, check if your volume justifies it. If you're planning more than ten thousand units, it's worth a serious look. Second, talk to an LDS material supplier — companies like RTP Company or BASF have design guides. Third, get a quick feasibility quote from an LDS service provider. They'll look at your 3D model and tell you if the geometry works. Luna: And what about the RF side? Do you need a specialist? Lucas: If you don't have RF engineering in-house, you'll want to hire a consultant for the antenna design. It's not something you can wing. But the cost is usually a few thousand dollars, which is small compared to the tooling investment. Luna: So the takeaway: LDS is a powerful technique for startups that are scaling production and want to reduce cost and improve reliability, but it requires upfront planning and a multidisciplinary team. Lucas: Exactly. It's not a shortcut — it's an engineering decision that pays off when you do it right. If your device needs wireless connectivity and you're designing a plastic enclosure anyway, you should at least consider embedding the antenna into the part itself. Luna: And if you want to learn more, we'll link to a few resources in the show notes. Thanks for listening, everyone.