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Supported holes, Solder, Vertical Fills, Hidden under connector body

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#81217

Supported holes, Solder, Vertical Fills, Hidden under connector body | 12 October, 2018

We have some fairly standard 0.1" pitch, two row, shrouded, through hole headers soldered onto a thick backplane. There are tiny inspection holes along the bottom edge of the plastic body that allow an inspector to observe the top of the through hole and the pin in it. However, they are so small and at a low angle that all that can be seen is whether or not the solder came to 100% fill or greater. It cannot be seen if it reached the 50%, 75% fill level or wetting to the destination side of the pin.

What are the requirements for Class 3 inspection in situations where fill cannot be seen because it's hidden by the component body?

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#81220

Supported holes, Solder, Vertical Fills, Hidden under connector body | 12 October, 2018

Feature||Class 1||Class 2||Class 3

Circular wetting of solder of the lead and plated hole barrel on the component side.||Not Specified||180 deg||270 deg

Plated hole fill.||Not Specified||75%||75%

Circular fillet and wetting of solder of the lead and plated hole barrel on the solder side.||270 deg||270 deg||330 deg

Percent of the land area covered with solder on component side.||0||0||0

Percent of the land area covered with solder on the solder.||75%||75%||75%

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#81221

Supported holes, Solder, Vertical Fills, Hidden under connector body | 12 October, 2018

Thank you. I have those requirements in our copy of IPC-A-610. My question is what are the requirements if we can't see into the hole to verify if the vertical fill is >75%?

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#81223

Supported holes, Solder, Vertical Fills, Hidden under connector body | 13 October, 2018

So, why do you think that the requirements for accepting a solder connections would change depending on whether the connection is or is NOT visible?

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#81233

Supported holes, Solder, Vertical Fills, Hidden under connector body | 15 October, 2018

Because if you can't see it, you can't verify it is acceptable or not.

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#81236

Supported holes, Solder, Vertical Fills, Hidden under connector body | 15 October, 2018

The methods of verifying PTH hole-fill.

1 Visual inspection

2 x-ray inspection works very well for inspecting such a connector for voiding and hole fill. View the connector off-vertical, at between 30 and 45 degrees. As always, the solder connection will be "domed." So, take your measure from where the solder joins the barrel of the hole, not the dome.

3 Qualification by implication, where the soldering parameters of an automated solder process are qualified and then validated with a set of microsections using a number of samples.

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#81250

Supported holes, Solder, Vertical Fills, Hidden under connector body | 17 October, 2018

We had a selective solder installation tech raise the connector body off of the PCB slightly with a spacer to allow for a visual inspection to verify the process/profile.

A few years back we invested in a large enclosure X-ray with a manipulator arm to tilt and lean the assembly in all directions to verify barrel fill. It was 50K, but has paid for itself already in house and with customers questioning barrel fill. One of our better, quality related investments.

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#81252

Supported holes, Solder, Vertical Fills, Hidden under connector body | 17 October, 2018

Thanks for all the input!

I should clarify a couple things. We are a contract manufacturer; we simply build to our customer's design prints. This particular board, we outsourced because of some requirements for processes we don't do in-house. So, we are stuck to inspecting to the drawing requirement of IPC-A-610 class 3. We aren't going to section because that requirement wasn't priced into the job or required by the contract.

The holes I mentioned for inspection are actually for cleaning after processing. Even if we made these boards ourselves, one limiting factor is the presence of internal copper planes inside the board that suck up heat and limit the flow of solder. Sure, proper pre-soak would take care of that, that's why the exception below in the IPC requires verified process control.

The real question then, is, is there an exception to IPC requirements for vertical fill (sect 7.3.5.1.) when you can't see the interior of the hole?

Someone sent me this by email: IPC-A-610G 5.2.14 states that partially visible or hidden connections shall be inspected on the visible portion and the non-visible shall be in accordance with clause 1.6. The J-STD has the same exception but includes three conditions for acceptability, design doesn't restrict flow, visible portion is acceptable, and process controls are maintained to ensure acceptable and repeatable results.

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#81257

Supported holes, Solder, Vertical Fills, Hidden under connector body | 18 October, 2018

David, you can beat around the bush interpreting criteria, but without X-ray you will not see anything. This is the way to go to inspect this solder joints properly. Criteria is 75% fillet and than you have circumference, air gaps in there....

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#81258

Supported holes, Solder, Vertical Fills, Hidden under connector body | 18 October, 2018

I understand and agree. However, we are not on contract to provide x-ray inspection and I could certainly not get a purchase of one approved for this one project.

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#81266

Supported holes, Solder, Vertical Fills, Hidden under connector body | 18 October, 2018

Yes, send them out or take a few samples and go to a place where you can use the machine or be with the product -based on the product security required. That way you can remove or confirm your suspicions.

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