I’ve noticed that many consumer power adapters and small appliances use single-sided FR-2 boards with through-hole components. Is it just about cost and wave soldering, or are there other manufacturing advantages to using FR-4 or multilayer boards?
1 Like
Cost is generally the largest driver for low tech items and product lifecycle is generally not considered as critical. Many consumer items are built in huge quanties and any penny saved adds up over high volumes.
Multilayer layouts or higher quality board materials are considered when design requirements forces that added cost.
2 Likes
One manufacturing advantage of FR-2 boards is that they can often be die-punched instead of drilled. In high-volume production, a stamping die can create all the holes and board outline in a single operation, which is much faster than mechanically drilling thousands of holes.
FR-4 boards contain fiberglass and typically require drilling, which adds time and tooling cost. For simple single-sided power supply boards produced in very large quantities, the punchable FR-2 process can significantly reduce manufacturing time.
2 Likes
Another practical reason is electrical requirements. Many offline SMPS designs don’t need controlled impedance, high layer counts, or dense routing. The circuits are usually relatively simple and operate at lower frequencies where a single copper layer with jumpers or clever routing is sufficient.
Also, FR-2 has adequate dielectric strength and isolation for many mains-powered designs, which is important for primary-to-secondary safety spacing. As long as the board meets creepage, clearance, and thermal requirements, there’s often no technical advantage to using FR-4 or multilayer boards for these simple power supplies.
2 Likes
Another item to note. Single layer low cost thru-lead products generally do not include plated holes. This is cheap to produce however the resulting assembly is not as reliable as boards with plated holes. Many years ago I did consumer product service and the single highest failure was crack solder connections since the holes were not plated.
Normal temperture cycling was hard on solder connections over time and not having solder being able to adhere to a plated hole barrel minimized the overall amount of contact area between the board copper and the component leads.
2 Likes
That’s a great insight, I hadn’t considered the long-term reliability impact of non-plated holes. It seems like a clear trade-off between cost and durability.
1 Like
Thanks, everyone. This was really helpful. It looks like the choice of single-sided FR-2 boards is a combination of high-volume manufacturing efficiency, sufficient electrical performance for simple SMPS designs, and overall cost optimization. Appreciate all the insights!
1 Like