93
votes
Accepted
Why does a commercial PCB need this much rework?
This looks like it's due to a combination of bad engineering, bad management, and cheap labor.
Circuits don't always perform as expected when first designed. Even experienced designers make mistakes ...
- 314k
90
votes
Accepted
How do I identify SMD components? (or how do I identify any component)
Step 1) Identify the package, note how many pins, match up the pins first. Note that sometimes the package pins are underneath the part or extended away from the part. Also get the dimensions of the ...
- 87.1k
85
votes
Do dead weight 'components' exist?
Power your board from a 12V 7AH Sealed Lead Acid Battery. Then hot melt glue your board to the side of the battery.
Similar to the ideas shown by @DaveTweed I have mounted prototype parts to a piece ...
- 57.6k
73
votes
Do dead weight 'components' exist?
When prototyping, I often run into the same issue. What I usually do is find a sheet of suitable material that's larger than my board. It can be anything — wood, plexiglass, scrap PCB material, ...
- 176k
60
votes
Accepted
Why are GND pads often only connected by four traces?
This is to make soldering easier. Those 4 traces make it easier for the pad to heat up as the heat can only escape through those 4 traces. Soldering to a GND pad is difficult enough as it is, but if ...
- 12.1k
58
votes
Accepted
What did the manufacturer mean by asking if an angle should be made for the fingers?
When they say 30° degree, I think they mean to chamfer the end of the edge connector for easy insertion into the C64 cartridge slot.
When they do that, you will probably lose the last mm of copper ...
- 3,807
55
votes
Accepted
Is it OK to route a trace through a pad?
There is no problem routing traces through pads (like you have done). Be aware when routing power/GND of the current that will be travelling through these traces. This will dictate trace thickness. In ...
- 1,622
50
votes
Why don't we have very high layer count PCBs (usually a maximum of 4-6 layers)?
Let's have a look at this iPhone PCB.
Notice there are no traces, only pads with devices stuffed right next to each other everywhere on both sides.
This is HDI (High Density Interconnect).
This is ...
- 80.3k
49
votes
Accepted
Different PCB color (is it a different material?)
The green areas have been coated in solder-mask.
The yellowish area is simply the base color of the PCB material, which has not been coated.
It's the same base material throughout.
You would ...
- 14.8k
45
votes
Accepted
Have I placed too much on this PCB layout?
I assume that you are using the autorouter because you think it will save your time. But I have some bad news: it is said that PCB layout is 80% component placement, 20% routing. You can't just slap ...
- 12.6k
44
votes
Accepted
Would you approve use of these PCBs??? Delamination issue
The fact that they delaminated in only a year calls into question the quality of the workmanship, regardless of the fact that they were in storage. Like you said, if they delaminate in storage they ...
- 21.5k
42
votes
Accepted
Why is there a little nose on the PCIe connector?
According to the PCI Express Card Electromechanical Specification 1.1 it is to prevent insertion into a standard "non-express" PCI socket.
http://read.pudn.com/downloads166/ebook/758109/...
- 1,369
42
votes
Accepted
Writable area on a PCB
Assuming white silk screen, just draw a solid box on the silkscreen layer.
You can then write on it with a permanent marker.
Here is an example from a board I made a while back:
That was before I ...
- 68.7k
41
votes
Accepted
If the silicon wafers from which the processors are made are so sensitive that workers wear special suits how is delidding a processor possible?
Wafers are extremely sensitive during manufacture, because if any dust or dirt particle settles on it between any process steps, then the following process steps will fail on the contaminated spot.
...
- 80.3k
41
votes
Accepted
Why is there a difference between pad-to-trace and trace-to-trace clearance?
But it makes me wonder why the PCB manufacturer sees the 2 as
different things.
It's likely that this is due to the solder mask tolerance.
With two side-by-side tracks, the solder resist ...
- 466k
40
votes
Accepted
What's the meaning of Electrical Inches?
"Electrical inches" is shorthand for "inches of trace along which the electrons must flow". In other words, it's the length of the wires or traces, following any bends, not the straight-line distance.
- 176k
40
votes
Accepted
What is the meaning of this datasheet diameter notation?
It means that there are 5 (quantity) of these holes, each has a diameter of 1.2 mm (+0.1 mm / -0 mm).
- 18.3k
38
votes
How to secure cables to a PCB
Zip ties are a good way to provide strain relief for cables attached to a PCB. You lay out a path for the cable on the PCB, and put adequately large holes on either side of this path for the zip tie.
...
- 176k
38
votes
Accepted
Connecting 10AWG wires to PCB
My general strategy for dealing with vibrating wires is to provide strain relief. I would consider adding holes in your PCB specifically for wire retention, like in the image below. You can use ...
- 2,261
36
votes
What did the manufacturer mean by asking if an angle should be made for the fingers?
It is my understanding that they are asking if you want them to bevel the PCB where the connector is located.
Here is an illustration from Eurocircuits demonstrating the end result:
If you look at ...
- 14.5k
36
votes
Accepted
What is the purpose of those star like solder joints?
This patent from 2005 claims the idea (star shaped solder pads) and gives the motivation to be the desire to simplify the manufacturing process for boards that require both SMD and leaded components. ...
- 1,281
35
votes
Accepted
What is the purpose of two cylindrical holders in RJ45 female connector for PCB
These are strain relief fittings. They spread the horizontal force that's exerted when you insert or remove the connector from the socket. This helps prevent the electrically connected pins being ...
- 7,969
35
votes
Accepted
In PCBs, why is copper etched away instead of added?
I know that in virtually every case, PCBs start as a substrate with a layer of copper laminated on top, which is then etched away, leaving the traces.
This is not fully correct: in modern PCB ...
- 9,021
35
votes
Aluminum bus bars connection to PCB
If you want the bar to be flush against the PCB, consider broaching PCB PEM nuts.
If you want to raise the bus bar, consider pressfit threaded terminals.
https://www.digikey.com/short/2hm8p02f
If ...
- 23.9k
33
votes
Accepted
What are these round pads on the bottom of a PCB?
As mentioned in some of the comments, these are test pads designed for use with a pogo-pin test fixture, also known as a bed-of-nails test fixture. These fixtures have a specially-shaped array of pogo-...
- 21.5k
33
votes
Accepted
Pattern on a PCB
The pattern is a pair of spark gaps, a kind of low-cost voltage limiter. The closely-spaced pointy conductors favor the formation of a spark, and the soldermask is removed (the tan rectangular area) ...
- 176k
31
votes
Accepted
72-pin SIMM RAM: how do ground (Vss) and supply (Vcc) voltage pins work
The board is a multi-layer stackup, probably 4-layer.
This means that there are more layers inside the PCB on which other connections are routed.
You can tell this from the seemingly disappearing ...
- 68.7k
31
votes
Accepted
How can I cover PCB burn marks to identify burns later?
Non-reversible temperature-sensitive labels are available which will change colour irreversibly if they experience a defined temperature. These for example are 14 mm diameter which should be small ...
- 1,488
31
votes
Accepted
Fiducial marks: Do they need to be a pad or is it okay if I use the top silk layer?
You need to use a copper pad, with a corresponding clearance in the soldermask and ground planes.
The reason for not using the silk layer, is the tolerances of aligning the silk are typically ...
- 68.7k
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