Questions tagged [via]

In a PCB, a via is a plated hole that allows electric connection between layers. This is the more common use of the term on this site. In integrated circuit, a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers.

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10
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2answers
2k views

IC power pin connection for noise immunity and decoupling

There's been much talk on other Q&A threads on how to connect decoupling capacitors to an IC, resulting in two completely opposite approaches to the problem: (a) Place decoupling capacitors as ...
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2answers
5k views

Should you place traces at right angles through a via?

I understand that right angle pcb traces should be avoided because it can cause problems during manufacturing. But what about right angle through a via? Will this have any negative effects? I ...
25
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7answers
13k views

Optimize heat sink design - connect cooling pad on PCB backside by vias

In one of my current projects I'm using an MC7805 in a D2PAK package to generate my logic supply of 5 V from an available 24 VDC supply. The current required by the circuit is 250 mA. ...
27
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7answers
27k views

vias directly on SMD pads?

I was looking at an example board schematic provided by TI and I noticed something rather curious: vias were placed directly on SMD pads. Is this a normal/acceptable practice to follow? Or is it ...
20
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2answers
15k views

Castellated/Edge-plated PCBs: Comments on Mechanical/Electrical contact reliability

(This is a follow-up to this related question). I'm interested in some feedback from people's design results/experiences with Castellated PCBs as a method of attaching one PCB to another. By ...
6
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4answers
22k views

maximum via current carrying capacity pcb

As I know, there exist limits on maximum current, a pcb via can tolerate before it melts before the via's temperature rises unacceptably high above ambient (say 10-100 C above ambient depending on ...
6
votes
1answer
819 views

How to minimize characteristic impedance mismatches caused by vias?

This question springs from an answer here. When using stripline configurations for rf signalling, the conductors are routed on an inner layer of the pcb, sandwiched between two ground planes. I ...
20
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2answers
3k views

Can you place vias inside a QFN footprint?

I am designing a very dense PCB containing a 0.4mm pitch QFN chip. In parts it is proving very difficult to fan out. It is made all the more difficult by the huge thermal pad that all QFNs have for ...
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3answers
824 views

What is the best way to plate VIAs?

My local hackerspace has a CNC machine. I can give them my Gerbers and they can print out the PCB. The machine does not plate VIAs. I need to do this after the CNC machine is finished. What is the ...
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2answers
3k views

How to add vias and more traces?

I am getting a Drill Size error and overlapping errors because I added a new via and a wire to my PCB. I'm not really sure why I am getting these errors. Is there a way to add a new wire and get it to ...
13
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1answer
3k views

Why does reflection off a PCB via look like this?

My question is related to http://mobius-semiconductor.com/whitepapers/ISSCC_2003_SerialBackplaneTXVRs.pdf. On the page 18 there are a few figures of "TDR off Diferent Types off Vias". I am confused ...
16
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2answers
5k views

USB signal routing - Swap data lines using vias?

I'm making my second USB design, but the D+/D- pins on the MCU (atemga16u2) aren't in the right order for the micro B connector. What's the best practice for routing these to go the right way? My ...
6
votes
1answer
821 views

Additional signal plane vs lots of vias

I have a circuit that I am currently designing using a 4 layer PCB (signal, ground, power, signal). The PCB has rather a lot of vias to route the signals around the board (there are size constraints, ...
9
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1answer
10k views

How to connect ground planes together

What is the best way to connect ground planes together ? I know that ground planes are connected together at multiple locations in order to keep a low impedance GND across the whole board and provide ...
8
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1answer
324 views

Compensating for unbalanced via count in DDR3 routing

I'm working on a DDR3 layout at 533Mhz clock speed in a balanced T configuration. I am currently unable to route the address/ctrl lines with an equal amount of vias (+1 on a limited number of lines). ...
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3answers
10k views

Altium Thermal Pad shortcircuit

All my QFN footprints are made with the Altium internal "Tools -> IPC Compliant Footprint Wizard". I get nice footprints with vias in the thermal pad. When I try to place one of those footprints to ...
5
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2answers
3k views

Designing castellations/half holes using EAGLE

I wish to use some castellated pads or 'half holes' for board to board connections but I'm having a hard time finding a reference detailing how to specify these in my CAD package of choice (EAGLE). My ...
4
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2answers
830 views

What are the rules to make different drill pairs for VIAs in PCB layers?

Considering a 6-Layer PCB with the layer sequence as below: 1-Signal 2-GND_Plane 3-Signal 4-Signal 5-VCC_Plane 6-Signal -What are the considerations that I should take care of when making drill ...
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2answers
2k views

Vias without annular ring on internal layers, non-functional pads in a via

My PCB layout package (Altium) has an option to define the full stack of a via so one may have different sized annular rings on different layers. I was wondering if it is considered "manufacturable" ...
4
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3answers
5k views

Altium PCB Layout: The Difference of Through Via, Micro Via, and Burried Via

This is my very first time doing 4 layers PCB layout. What is actually the difference between Micro Via and Buried Via? Say I have Layer 1, Layer 2, Layer 3, Layer 4. What I know I use the Through ...
4
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1answer
3k views

Eagle via diameter discrepancy

I made a part in eagle with vias using a set diameter (smaller then auto), but when I use the part on a board, the vias go back to having a diameter of auto. any ideas? The left window shows the ...
3
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3answers
1k views

How do I know where to put stitching vias?

I'm working on a PCB that allows me to attach a TSSOP IO expander to a breadboard more easily for experimenting. I asked a question regarding the configuration of decoupling capacitors for an IC with ...
3
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1answer
2k views

Vias under thermal pads

I'm working on a design with MOSFETs and with the LT4415 device. The MOSFETs should dissipate an average heat of 0.45 W (with peak at 2 W but just a couple of seconds with several minutes to recover)...
3
votes
1answer
7k views

Thermal vias in Eagle (CAD)

I'm making a part in Eagle (4.15) for a SOIC-8 package. There is a thermal pad in the center and I'm trying to add vias stitching the top and bottom pads together. In the Eagle package editor there ...
13
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1answer
2k views

Using a via to strengthen surface mount connector on or near pad

I am trying to design a board that has a surface mount connector. I was shown a picture of an example board that has vias on the pads of the connector. I don't believe the via is for connecting to a ...
5
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1answer
411 views

Acute angle on a pad or a via

It is better to avoid acute angle to join two routes (depending on current direction and waveform). I often see on board acute angle with a pad or a via. Is it bad? Should it be avoided as well?
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1answer
88 views

Traces over ground plane [duplicate]

Sometimes it cannot be avoided to run traces over a ground plane (bottom layer) in a two layer PCB. I have two questions regarding this: In the (simplified) example below, what is preferred? To use ...
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2answers
937 views

Many small via vs few bigger via

While I was designing a board I thought, if we want to make a better path for the current what is the best choise? Small vias and big in numbers or fewer but with bigger hole?
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1answer
1k views

Calculating Signal Loss (dB) Through Vias

Does anyone have any useful calculations or links to material covering good ways to calculate signal loss through vias? What would be perfect is a graph with typical loss in dB over the range 1GHz ...
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3answers
241 views

Double side PCB with solder via?

Normally vias are made with through hole plating. In the past they used to make vias by soldering a piece of wire to connect the top and bottom layers (like a short piece of 24 gauge copper wire). ...