Vias on pads at JLC assembly

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mrand
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Vias on pads at JLC assembly

Post by mrand » Mon Jan 11, 2021 10:03 am

Hi folks,

I've always placed vias right on the SMD pads whenever needed. I've had many board like this assembled at JLC with no problem. Today, however, I received a message regarding my current order stating that there "seems there are some holes on the pads. when proceeding to reflow, the solder paste will probably flow through the hole to the backside of PCBs, and it will probably cause bad soldering"

Are other people placing vias right on their pads? Any experiences with this?

Thanks!
Colin
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jorg
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Re: Vias on pads at JLC assembly

Post by jorg » Mon Jan 11, 2021 11:38 am

At my employer, it would be unacceptable to place a via on a pad. JLC is correct.

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Flounderguts
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Re: Vias on pads at JLC assembly

Post by Flounderguts » Mon Jan 11, 2021 11:53 am

Yes, but it works anyway.

I would not do it normally, just because I like to see where the vias are. But there is no reason not to on a modular synth, as long as you aren't assembling with a relatively small-ball solder paste.
If you're using hard solder, it should be fine.

Having said that, if JLC is doing the assembling, I'd probably listen to them.
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pjbulls
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Re: Vias on pads at JLC assembly

Post by pjbulls » Mon Jan 11, 2021 12:00 pm

I put a lot of vias on my pads, but always solder manually. It is true that it can mess up automatic assembly for the reasons mentioned, so it is safer to put them besides the pads if possible.

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MikeDB
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Re: Vias on pads at JLC assembly

Post by MikeDB » Mon Jan 11, 2021 12:08 pm

They don't want paste going down the via as it will expand in random ways during reflow. Some PCB places offer via in pad but they use special processes.

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cackland
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Re: Vias on pads at JLC assembly

Post by cackland » Mon Jan 11, 2021 4:12 pm

Surprised JLC actually accept it for manufacturing anyway.. I’ve asked them before and told me they don’t accept via in pad manufacturing.

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ansome
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Re: Vias on pads at JLC assembly

Post by ansome » Mon Jan 11, 2021 4:31 pm

I have ordered a few PCB's from JLC with via's on the pads and never had any issues

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Re: Vias on pads at JLC assembly

Post by Flounderguts » Mon Jan 11, 2021 6:23 pm

I just spoke to my JLC rep. He told me they have 3 different manufacturing facilities, and the newest one will not do vias on the pads...something to do with a new reflow process that uses a less viscous solder formula for environmental reasons.

In other news, they agreed to fold and fix a set of pcbs for us at almost no extra cost! Say what you will about Chinese manufacturers, these guys have really bent over backwards for us!
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mrand
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Re: Vias on pads at JLC assembly

Post by mrand » Wed Jan 13, 2021 10:34 am

I can't believe I've been doing vias under pads at JLC assembly for a whole year now and never knew it was a bad idea!
Sounds like I'll need to fix a few designs :doh:
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Elahrairah
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Re: Vias on pads at JLC assembly

Post by Elahrairah » Wed Jan 13, 2021 7:56 pm

Seems it has to do with paste application for the reflow soldering step; that's only applicable if you are using their assembly service.

If you're getting bare boards back to solder by hand with solid stuff, it wouldn't be a problem.

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