Author Topic: Is it possible to route this in 4 layer 5cm x 5cm?  (Read 1714 times)

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Offline TomS_

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #25 on: December 03, 2019, 01:33:25 pm »
I don't know if it is possible to do a oven-reflow of a PCB populated on both sides? If I only put lightweight caps on the bottom layer I could probably reflow them first and then do the top side while the components on the bottom side are taped with kapton?

I have seen some people suggest using a solder with a higher melting temperature for the first side/load, such that when flipped over and reflowed for the other side using a solder with a lower melting point, the first side ideally doesnt melt and everything stays in place.

Otherwise, you can probably help your layout a bit if, for example, you disregard the order of the address and data lines of the SRAM chip. Assign them according to what is easiest to route, since it doesnt particularly matter what order the bits are stored, and jumbled up address lines just results in data being written all over the chip.

The flash chip will need more attention to in-order data and address signals, unless you write some tools to slice up your resulting binary image and jumble it around to suit - it has been done before! check out mikeselectricstuff on YouTube where he talks about a printer buffer he designed and used that very technique.
 

Offline EEVblog

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #26 on: December 04, 2019, 04:58:13 am »
I don't know if it is possible to do a oven-reflow of a PCB populated on both sides? If I only put lightweight caps on the bottom layer I could probably reflow them first and then do the top side while the components on the bottom side are taped with kapton?

Absolutely no need for double sided load here, you already have plenty of space on the top side.
You can gain even more space by using smaller passives, 0402's will work wonders.
 

Offline ebclr

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #27 on: December 07, 2019, 12:43:19 pm »
Did you check the price on pcbway ? Is 28 USD for 100mm X 100mm 4 layers
 

Online Yansi

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #28 on: December 08, 2019, 10:36:46 am »
PCBWay shill?  ;D   JLCpcb will costs half that and even less with the free eevblog coupon code.



 

Offline ebclr

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #29 on: December 08, 2019, 11:51:43 am »
It's not true, that JLCPCB is always a cheap supplier,  boards on size between 50x 50 and 100x 100 are very often beaten by PCBway on a large margin

A 53X 63 mm 2 layer board costs more than double on Jlcpcb than on pcbway, On very small boards with less than 50 X50 mm JlcPcb is a winner, but on the middle range size, isn't. Just check for yourself before post comments that do not match reality


Where is this " free eevblog coupon code."
« Last Edit: December 08, 2019, 12:09:08 pm by ebclr »
 

Online Yansi

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #30 on: December 08, 2019, 11:54:05 am »
You wrote 100x100x4L.  So I countered with what appears to be more than 0.3 orders of magnitude better to fit that requirement. Don't twist the topic to shill PCBway and do not try to insult others, because you even can't follow yourself.

//EDIT: If you don't see the code, you shall visit your ophthalmologist. It is hanging there for more than month on the top of the forum.
« Last Edit: December 08, 2019, 11:56:25 am by Yansi »
 

Offline ebclr

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #31 on: December 08, 2019, 12:12:04 pm »
"do not try to insult others, because you even can't follow yourself"

What did you smoke today?
 

Online mikeselectricstuff

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #32 on: December 08, 2019, 12:25:43 pm »
My approach would be routing it like this and if it doesn't work out somehow re-arrange the components and then try again.
Placement is everything.
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Online mikeselectricstuff

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #33 on: December 08, 2019, 12:27:01 pm »

I don't know if it is possible to do a oven-reflow of a PCB populated on both sides? If I only put lightweight caps on the bottom layer I could probably reflow them first and then do the top side while the components on the bottom side are taped with kapton?

You don't need to do anything to stop bottom-side parts falling off on the second reflow - surface tension will hold them.

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Online Yansi

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #34 on: December 08, 2019, 12:45:43 pm »
"do not try to insult others, because you even can't follow yourself"

What did you smoke today?

Your arguments are only supporting mine. Go outside and chill, please. I'll gladly follow, but please read the below first:

PCBWay is reporting me $51 for 100x100x4, JLCPCB is reporting $28 for 100x100x4 and even with DHL Express shipping included, I am still below the price of PCBway. Not sure where did you smoked out those 28$ for PCBway.

If PCBWay would be cheap, I'd have probably used it in the past - didn't happen, because it never actually was cheaper for any boards I did in the couple years back.

Maybe you see different prices, but I work with what I got. (Mainly through PCBshopper. And if some manufacturer happens to report incorrectly, sorry to them, but not my issue. I have also tried switching different countries, including EU and US. JLC still way cheaper, than your PCBway, for your original 100x100x4L suggestion.)

In any case, with any of these prices, I still do not see why an inexperienced designer shall push 0.8 pitch BGA on a small PCB, as hs first 4L design. That is not likely to happen. Any of these prices are more than likely couple times below what would a local pcb fab quote for a single prototype PCB.
« Last Edit: December 08, 2019, 12:47:51 pm by Yansi »
 

Offline OwO

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #35 on: December 08, 2019, 01:18:59 pm »
You are probably going to want to use the prototype assembly service though. I definitely don't miss manually soldering passives or even stencil + hand pick and place of 200 parts. That way I don't think about skimping on decoupling caps or stitching caps. and can do really dense boards. 5x5 cm is not necessarily a good deal though as you can get 4 times the prototype area for twice the price. I usually can fill a 10x10 cm panel easily and have done up to 10 different designs on a 10x10 panel (they don't charge extra if you don't add milling slots).
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Online ebastler

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #36 on: December 08, 2019, 01:50:00 pm »
A 53X 63 mm 2 layer board costs more than double on Jlcpcb than on pcbway, On very small boards with less than 50 X50 mm JlcPcb is a winner, but on the middle range size, isn't. Just check for yourself before post comments that do not match reality

Hmm, let's see. For the default parameters, i.e HASL with lead, green solder mask etc., I get:

$2 on JLCPCB vs. $5 on PCBWay, quantity 5.
Or $5 for either supplier at quantity 10.
At higher quantities, JLCPCB wins hands-down again, e.g. $24 vs $61 at quantity 100.

Did you check prices for yourself before posting?
 

Online Simon

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #37 on: December 08, 2019, 04:12:17 pm »
Quote
you can use any connector or even test points and pogo pins for JTAG, just make a cable to fit
I thought it would be nice to have a fitting receptacle, but you are probably right.

Putting caps on the bottom is definitely a thing I am going to consider.

I have not used them yet but Wurth do a series of connectors called SKEDD that just plug into pads on a board.
 

Online Yansi

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Re: Is it possible to route this in 4 layer 5cm x 5cm?
« Reply #38 on: December 08, 2019, 04:39:33 pm »
Beware that these SKEDD connectors I think have pretty low mating endurance, so probably not great for production programming. But for home-gaming and prototyping, they are great.
Also I think they need more board area per number of pins, than  equivalent standard .1" header.

There also double density .05" pin headers, that may be (and often are) used as JTAG/debug interfaces on various boards. These can be fitted on the respective gray ribbon cables with .025" pitch (0.635mm).
 


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