Naked ground plane PCB (what's the proper name) - Page 1
Forum section: electronics / beginners

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 26, 2018, 05:26:03 am
content: What's the proper name (if any) for the following type of PCB with that naked copper shield. It's from a late 1980s Philips CD player:

author: eb4fbz
author_rank: Regular Contributor
timestamp: May 26, 2018, 03:51:23 pm
content: Ground plane? Maybe you are confused because of the fact that metalized vias didn't exist in those days, so ground connections were done using wire jumpers.

author: Kalvin
author_rank: Super Contributor
timestamp: May 26, 2018, 04:00:16 pm
content: Quote from: eb4fbz on May 26, 2018, 03:51:23 pmWell, the better explanation is cost optimization. Typically consumer electronic devices used similar method of using jumper wires in order to avoid having a through-plated PCBs.

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 26, 2018, 09:10:34 pm
content: Quote from: eb4fbz on May 26, 2018, 03:51:23 pmThere are SMDs on the other side of that PCB, so there are vias.The copper plane your see on the component side is (0v, common), and both digital and analog devices arecommon(grounded) to it.Schematics for this 1988 device are here if anyone is curious:https://www.hifiengine.com/manual_library/philips/cd473.shtmlBTW: The query remains unanswered: if this style of "naked ground plane" is not a ground plane, what's the proper name.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 26, 2018, 09:41:52 pm
content: Quote from: eb4fbz on May 26, 2018, 03:51:23 pmWTF???

author: Gyro
author_rank: Super Contributor
timestamp: May 26, 2018, 09:49:01 pm
content: Quote from: 13hm13 on May 26, 2018, 09:10:34 pmThe proper term is 'Ground flood'.

author: Gyro
author_rank: Super Contributor
timestamp: May 26, 2018, 09:54:14 pm
content: Quote from: Alex Eisenhut on May 26, 2018, 09:41:52 pmHe's right in that you didn't / still don't get vias in cheap SRBP board like Philips used. Double sided is pretty rare in itself.

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 27, 2018, 12:58:10 am
content: Quote from: Gyro on May 26, 2018, 09:54:14 pmWhat's your definition of "VIA"?Wiki notes:"In printed circuit board design, a via consists of two pads in corresponding positions on different layers of the board, that are electrically connected by a hole through the board. The hole is made conductive by electroplating, or is lined with a tube or a rivet."Look carefully at the PCB photos in my prev. posts (component and solder side).

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: May 27, 2018, 04:29:13 am
content: I have always known it as a "ground plane" and even in broadcast video in the mid - 80's it was always put on the component side to separate the tracks on the solder side from the components.But I agree with everybody else in that 2-sided pcbs in consumer stuff from that era was fairly rare. Single-sided boards always seemed to offset the added cost of jumpers, even if the boards were hand-loaded.

author: Gyro
author_rank: Super Contributor
timestamp: May 27, 2018, 09:14:07 am
content: Quote from: 13hm13 on May 27, 2018, 12:58:10 amYes I know, I've worked on those Philips CD player boards. Non of the holes are plated through (Vias). SMD doesn't automatically mean vias.Actually, they used a rather irritating grounding strategy. Non of the IC ground pins are directly soldered to the ground flood / plane - the only ground connections are those wire links with the solder 'blob' in the middle. The ground was then tracked on the underside to the ground nets. By doing this, they lost a lot of ground integrity compared to a proper ground plane. They also slotted it to hell.The ground and therefore supply noise is particularly bad around the SAA7220 digital filter, leading to its bad reputation and many conversions to 'non-OS' - you can see a badly implemented one in one of your photos (the overlong black wires).

author: eb4fbz
author_rank: Regular Contributor
timestamp: May 27, 2018, 09:50:05 am
content: Quote from: 13hm13 on May 26, 2018, 09:10:34 pmUsing SMD components doesn't mean there are vias. There are no plated vias in that board, and ground connections to the ground plane are done using wire jumpers with a solder blob in the middle at the ground layer. Unplated holes are just holes, not vias, and IC ground pins are not directly soldered to the ground plane to reduce costs.

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 27, 2018, 04:07:14 pm
content: Quote from: eb4fbz on May 27, 2018, 09:50:05 amI never meant to imply that -- apologies for the confusion. However ...QuoteIf a wire (or "connector") goes thru a hole in the PCB, at strategic positions, to that Cu plane on the component side, isn't that a "vertical interconnect access" ... or just a "jumper"?BTW: a riddle for those playing along at home:That whole (stuffed) Philips board may contain MANY, MANY vias of the kind everyone can agree upon. Where are they?

author: Gyro
author_rank: Super Contributor
timestamp: May 27, 2018, 04:21:26 pm
content: No, sorry. The definition in of a via in a PCB is very clear, a via is a part of the PCB itself. The creation of vias is part of the bare PCB manufacturing process.Every connection on that board is either a component leg or a wire, inserted through a non-plated hole or a surface mounted part. No vias, no riddle....Quote from: 13hm13 on May 27, 2018, 12:58:10 am

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 27, 2018, 04:22:32 pm
content: Quote from: Gyro on May 27, 2018, 09:14:07 amPersonally, even with the stock Philips player, I prefer the oversampled sound over NOS.There are several other issues with the 7220 that de-optimize its performance. One main one: it being used as a clock divider (divider by 2, for the good of the downstream TDA1541 dac). But, also: the clock signal to the upstream decoder (SAA7210) being routed thru the noisy 7220.The SAA7220 is a pretty good digital filter if implemented right. Many high-end audio companies (esp in UK: Creek, Naim, Arcam), continued to use it (with its partner TDA1541), in various CDP models, almost into the new millennium.

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 27, 2018, 04:24:09 pm
content: Quote from: Gyro on May 27, 2018, 04:21:26 pmRe-read the riddle .. .and try again

author: free_electron
author_rank: Super Contributor
timestamp: May 27, 2018, 05:02:50 pm
content: Quote from: eb4fbz on May 26, 2018, 03:51:23 pmCheck your 'facts'... they've been around since before ww-ii ...this is a simply phenolic paper board. the holes are punched , not drilled. this process is not usable for plating via's.dirt cheap board.

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 27, 2018, 08:10:37 pm
content: No takers on the riddle?Read the riddle query carefully and, possibly, refer to the Wiki article on VIAs

author: eb4fbz
author_rank: Regular Contributor
timestamp: May 28, 2018, 03:26:51 pm
content: Quote from: 13hm13 on May 27, 2018, 04:07:14 pmI call them jumpers instead of vias because it's what they are: a jumper with a solder blob in the center at the ground plane side.If they were wires or rivlets soldered at both sides of the PCB, like a homemade via, i would have called them vias.