Electronics > PCB/EDA/CAD
PCBWay issue with QFN solder bridge, what to do?
VEGETA:
your suggestion seemed ok with me. I mean using smaller holes and plugging them then use good amount of solder to fully seal and solder the IC... all this durring manufacturing the production units.
if this batch of just 2 assembled boards worked, which it will unless something majorly wrong is there.... i will make another small batch of say 5-10 assembled boards using the 0.2mm hole vias (exactly the same as datasheet) and plugged holes.
if that also worked, then i will use it for all production in the future.
i just wanted to do one iteration of prototypes instead of 2, but as you said, can't get it right the first go.
westfw:
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I don't know how much good those "thermal vias" are going to do without a substantially more "solid" ground plane on the other side of the PCB. A lot of those SMPS chips seem to assume a 4-layer board with the bottom layer being almost solid ground plane.
For maximum heat sinking, you WANT the vias to get filled with solder - a solder-filled via should be significantly more thermally conductive than a via with just plating or non-metallic fill. I don't know how to balance that with the "wicking" problem that others are concerned about :-(
VEGETA:
--- Quote from: westfw on October 27, 2022, 01:31:30 am ---
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I don't know how much good those "thermal vias" are going to do without a substantially more "solid" ground plane on the other side of the PCB. A lot of those SMPS chips seem to assume a 4-layer board with the bottom layer being almost solid ground plane.
For maximum heat sinking, you WANT the vias to get filled with solder - a solder-filled via should be significantly more thermally conductive than a via with just plating or non-metallic fill. I don't know how to balance that with the "wicking" problem that others are concerned about :-(
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the bottom layer is all ground plain, which is what you mentioned here.
the boards are on route to me, without resin filling. and from picture it looks like there is no wicking or spillage.
balance is what we do here xD :-DD so kindly mention you balancing theory :-+
VEGETA:
Hello
the boards arrived in Amman Jordan but will need time to get to me, will examine then but from pictures sent by manufacturer there does not seem to be any leakage.
However, I asked for a quotation of just PCB manufacturing using 3 options and here are the results:
1- via on pad without filling (our current options):
5 pieces = 44.14 USD.
20 pieces = 53.65 USD.
100 pieces = 93.81 USD.
2- via on pad with copper filling (what is considered to be the best):
5 pieces = 431.09 USD.
20 pieces = 431.09 USD.
100 pieces = 486.61 USD.
3- via on pad with resin filling:
5 pieces = 268.79 USD.
20 pieces = 268.79 USD.
100 pieces = 349.94 USD.
huge price increase as seen! components + assembly for 20 boards is about 500$ while it is about 1400$ for 100 boards. selling this for 50$ seems ok if I choose no filling and 100 quantity as it seems, especially that there is customs which is a giant monster here!
for 100 quantity: without filling = ~1500$ -> = 15$ per one unit + 5$ per unit as approx. customs = 20$ per unit total. sold for 50$ is kinda ok. however going for filling will make it harder. resin will make it about 23$ per unit and copper will make it more than 25$.
for 20 quantity: without filling = ~550$ -> ~35$ per unit including customs...
is 20 quantity as above good for first batch?
what will you do if you are in this situation?
if i got them as non filled, then checked the boards manually to remove the leaked solder will it be ok? or maybe reflow it from the bottom using soldering iron.
for your kind suggestions.
ataradov:
For small quantities like this, I'd go with the cheapest option. If something fails on a couple units, you can always manually rework them. The real issue starts when you need to make 1000+ of them.
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