Electronics > Beginners
PCB trace "style" between AC (mains) and DC circuits
niconiconi:
--- Quote from: T3sl4co1l on December 16, 2019, 12:03:07 am ---I've always wondered what tools are used, because this isn't anything new, they've been doing it for decades. It's not confined to power supplies -- though you see single-layer phenolic builds there most often, for whatever reason -- you see it on VCRs and TVs, too. I assume the smoothly curved examples are hand made (mostly ending in the 70s) and the rectilinear ones (mostly starting in the 80s) are EDA.
What's the most popular Japanese EDA tools?...
Ed: here's a Sony example, two layer board from a Trinitron monitor. https://www.seventransistorlabs.com/Monitor/Images/Defl5_a.jpg
Tim
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A lot of cheap boards from China also heavily use this routing technique. Nowadays, low-cost power supplies are the few remaining applications that are still using a single/double-layer phenolic board, so you are most likely to find them on power boards. But I see a large number of the cheapest board they sell online (e.g. "soldering practice 101" NE555 boards) use this routing style as well.
I, too, wonder what CAD packages they are using to create them. It seems the software can automatically "floodfill" every trace on the board.
SeanB:
--- Quote from: temperance on December 18, 2019, 07:32:41 pm ----Those low cost power supply boards are produced with phenolic paper. The wider traces make for extra stability.
-I've seen only one cad package able to this: PAD's. PAD's supports different routing modes.
Other tools able to do this must be available because commercial products with phenolic paper based PCB's in them are all "routed" like the boards you've shown. Those Pioneer DJM CD players are mostly made with phenolic paper PCB's and ten billion wire bridges with different lengths. They even wave solder very large TQFP's onto the bottom of such boards. Those bridges seem to be a cost effective solution compared to double sides epoxy PCB's. The same goes for flat screens. The interface boards are just phenolic paper when possible with a lot of wire bridges and big fat traces to keep traces from peeling of the board. Especially around connectors. The weirdest thing I've seen is a double sided phenolic paper PCB in a commercial product with wire bridges soldered with a wave soldering process for the bottom side and the top solder joints must have been a hand soldering job. Even on some trough hole components, they hand soldered some pins onto connections on the top layer.
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Just took apart a dead Sharp calculator, made around 2005. Toshiba main chip, SRBP board and with a whole 2 SMD transistors under the board, the rest being through hole parts, and around 30 jumper wires, in a set of 3 different sizes for the board. Matching keyboard SRBP board, single sided, wide and narrow traces, with carbon printed contacts, along with the jumpers being carbon printed over the soldermask , with a further soldermask layer screen printed over for protection.
With the thinner mass produced SRBP boards they do not actually drill the holes, but instead use a punch and die set, to make them all in a single pass with a press, saving time. There you want a wide pad and trace, as your alignment might be a little off, but so long as it still is mostly in place it will solder, and work, plus the die and punch has a much longer life over a speeding drill bit, which has a limited number of holes it can drill before it blunts and needs to be redressed.
A wide trace is also much less likely to fracture all the way through if the board is cracked during processing or shipping, so lessening the chances of the device failing during the short warranty period, though the crack may eventually go all the way to open later.
iroc86:
Thanks for the additional feedback, guys. It's sounding like this trace design is more due to mechanical reasons than anything, at least on the cheap phenolic boards.
Just for kicks, I reached out to Texas Instruments directly to inquire about the traces in the last set of attachments I posted, the ones for the TIDA-00701 power supply. This is a reference design that'd presumably be manufactured with regular FR4, which is the method TI chose based on the pictures in the preceding link.
They referred me to their "E2E" (engineer-to-engineer) forum, so I posted the question there. You can read the full thread here. I don't really feel that the TI engineer answered my question to the level of detail I wanted, but I wasn't going to push it further. They just reiterated the obvious, that traces need to be sized for current capacity and clearance/creepage. No real mention of the specific geometry aside from designer preference and the bit below about filtering performance:
--- Quote ---For the layout, you need to pay attention to below items:
1. the trace should have enough current capacity.
2. the distance between the traces should meet pressure requirement.
the layout in the picture is common and different designer has his own habit.
...
Oversize copper is intend to increase current capability and reduce the impedance. The trace around the pad is narrow which can make the capacitor/inductor play a better role of filter. Also there are some habits of the designer when he did the layout.
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