Layer explanation in Altium

[P_C_B]

Hello,

I have tried to look around for the following information, but haven't got a clear explanation.
The image I have attached is for a 2 layer PCB that I have designed. The footprint is for a TO-263 component. During the design process, I used the SMD pads that Altium provides (through the Component Wizard by selecting the SOP component). The SMD pad has the following layers in it (also shown in the image): 1) Top Layer, 2) Top Paste and 3) Top Solder.

My understanding of the 3 layers is as follows:
1) Top Layer: This is the copper trace that runs on the board and is generally covered by the green mask above it. Upon scratching out a trace,
I observed that it has a copper color to it, i.e. golden-yellow-rust.

2) Top Solder: This is a negative mask, i.e. the places where it has exists (on the software), is actually where the green mask is removed on the actual board. This would expose the underlying copper.

The question at this point is that, I would expect to see the golden-yellow-rust pad below the mask. However when I got the board after manufacturing, I see that it is in fact silver in color. How has this happened?

This would suggest that it has something to do with the 3rd Layer that shows up in Altium, i.e. 3) Top Paste. So is the silver color because of the top paste layer? The top paste is for automatic board manufacturing as it helps the reflow soldering process etc.. But is that why the pads on the board appear to be silver.

Also what material is that silver stuff?

Thanks in advance

Link to image: https://imgur.com/a/u4ucNr3

 

[barry]

"Silver stuff"???? Do you mean solder?

The exposed magic silver stuff is because those are the areas where the component gets soldered to the board. There doesn't look like there's anything wrong with your board.

I think maybe you need to educate yourself about about what a PCB really is.

 

[andre_luis]

However when I got the board after manufacturing...

From the left photo above of the manufactured board, there are indications that you will have serious problems, such as what seems a surrounding track too close to the big pad - apparently in the same layer, top - as well as the fact that it is always recommended to extend the copper around this pad (properly covered with solder mask) in addition to the exposed area of the pad, so that some heat is dissipated by the additional area not capped by the component.

 

[barry]

There's not going to be much heat dissipated without some vias connected to a plane.

 

[P_C_B]

"Silver stuff"???? Do you mean solder?

The exposed magic silver stuff is because those are the areas where the component gets soldered to the board. There doesn't look like there's anything wrong with your board.

I think maybe you need to educate yourself about about what a PCB really is.

Thanks for your replies guys, perhaps I had not framed my question as well. Barry, since I have already designed the board, I am obviously aware of what pads are and what a PCB is. As far as educating myself, that was the goal by asking the question on this forum. I am in no way saying that I am an expert at this stuff.

Anyway, my question was why are the pads silver in color rather than having the ~golden color of copper and is that something one has to select in the software itself. Well after checking with the manufacturer, there are many ways to "protect" the pads of your PCB as exposed copper (the golden colored stuff) may oxidize and could potentially cause problems in the future. Some of the techniques to protect the exposed copper are as follows:

1) HASL
2) Immersion Tin
3) OSP
4) ENIG
5) Gold etc..

The manufacturer I used to get my board made, actually used the HASL process, this way rather than seeing the pads in the golden color, they appeared to have a silver color. This is not selected in the software but in fact done by the board manufacturer. One could opt for other techniques as well depending on what suits their needs and budget.

As for the heating and routing problems associated with the image, you guys are correct on both fronts, the board needs better designing, probably the 2nd iteration.

From the left photo above of the manufactured board, there are indications that you will have serious problems, such as what seems a surrounding track too close to the big pad - apparently in the same layer, top - as well as the fact that it is always recommended to extend the copper around this pad (properly covered with solder mask) in addition to the exposed area of the pad, so that some heat is dissipated by the additional area not capped by the component.

andre_teprom, would you suggest creating a land pattern larger than the one specified by the component datasheet? (specially for a component which has the TO-263 package, since heat could be an issue)

Thanks

 

[KlausST]

Hi,

Anyway, my question was why are the pads silver in color rather than having the ~golden color of copper and is that something one has to select in the software itself.

Pad finish (HAL, HASL, ENIG...) usually is defined when you order the PCB.
You are free to write some information on the layer outside the PCB area with such information.
Usually the PCB manufacturers have web interfaces where you can select the finish.

It seems you are not very experienced in PCB things.. and you do the ssmebling by hand:
Then I`d prefer HAL/HASL, because it is not that critical to solder when stored for a longer time.

ENIG is good for immediate automatic SMD assembling and small pad sizes. But ENIG is very thin plating.


Klaus

 

[andre_luis]

andre_teprom, would you suggest creating a land pattern larger than the one specified by the component datasheet? (specially for a component which has the TO-263 package, since heat could be an issue)

As stated above, it is only a recommendation, it is not mandatory; in the end it depends on your analysis as to the heat to be dissipated by the pad stuffy with the component just above, so it is up to you to decide.

 

[barry]

You need to do a thermal analysis. How much heat is the device going to dissipate? What's the ambient? Are you using a heat sink?