Electronics > Manufacturing & Assembly

JLCPCB x-ray report interpretation help

(1/4) > >>

davegravy:
Hi I used JLCPCB for assembly of my board with a Ublox LTE module. They sent me x-rays of the module and I'm concerned because I see circular/bubble-shaped voids or lighter areas over most of the pads. I've never reviewed an x-ray before so I hope I'm worrying needlessly.

I attached a sample x-ray and drew red arrows to examples of these voids. It's a bit hard to see because the module's subcomponents are overlaid.

The module integration manual is linked here, page 101 shows the pad layout:

https://content.u-blox.com/sites/default/files/SARA-R5_SysIntegrManual_UBX-19041356.pdf#page=101

thm_w:
Good answers were given here already: https://www.reddit.com/r/AskElectronics/comments/1gm6tna/jlcpcb_xray_shows_large_voids/

jayx:
These voidings are massive, I suspect the problem may be lack of solder. Ask JLCPCB about stencil gerber and check apertures size, also ask what stencil thickness was used (ublox datasheet recommend quite thick 150 µm stencil). Also I'm curious what x-ray brand they're using, perhaps you have non-cropped screenshot?

davegravy:

--- Quote from: jayx on November 08, 2024, 10:34:12 pm ---These voidings are massive, I suspect the problem may be lack of solder. Ask JLCPCB about stencil gerber and check apertures size, also ask what stencil thickness was used (ublox datasheet recommend quite thick 150 µm stencil). Also I'm curious what x-ray brand they're using, perhaps you have non-cropped screenshot?

--- End quote ---

Thanks for confirming my suspicion. I don't have non-cropped x-rays, seems to be a limitation of their automation or equipment.

I messaged them a couple days ago to notify of the problem and was told to expect an email reply. When I get a one I'll request the items you mentioned.

Is this an expected part of the development process or is this a major error on their part... or both? I don't see any means to specify the stencil thickness in their ordering interface except for the "other/comment" field provided.

I have fine pitch packages (e.g. UQFN) on the same PCB - I wonder if this maybe drove them to use a stencil thickness that's less than appropriate for the larger pitch Ublox module? I just learned about step stencils, is this something they'd likely use to accommodate varying component pitch?

The order stopped progressing in their online tracking, usually it would have shipped by now so they may be investigating. I'm not sure what a reasonable resolution to this looks like, or what I should push for besides information and suggested design tweaks. The modules aren't reworkable (I've tried and failed miserably on past revisions) but if they have enough contact to function I can still extract some value from validating aspects of the design. It would have been nice to do thermal cycling tests on this revision but that seems a bit fruitless now.

davegravy:
I just read the below in another thread relating to JLC PCBA


--- Quote from: mikeselectricstuff on October 30, 2024, 11:30:52 pm ---I got a message from JLC that they don't use the customer's paste gerber file, and create the stencil from the component footprints
--- End quote ---


I'd assumed they were using my gerber, now I undertand why jayx suggested requesting the gerber.

The Ublox module I'm using wasn't available in their library, so I had to request that they add it. From what I gather, this process involved them designing the stencil from the module's datasheet. Unfortunately, there was no opportunity for me to verify or review the stencil design before proceeding.

There was a mistake when they added the part, which resulted in the unit cost being incorrectly set to $0, and I couldn't submit the order until they fixed it. That speaks to their QC when adding new parts.

I'm hoping the best-case scenario is that the stencil design has some minor issues, like too small aperture, that could be corrected once they address it. I would rather it be something adjustable, like the stencil, than an issue with the paste or reflow profile, which might be more difficult to rectify.

Has anyone else run into this issue with Global Sourcing, or have tips on how to handle such stencil discrepancies (short of switching providers)?

Navigation

[0] Message Index

[#] Next page