Through-hole pin length and PCB thickness

[fitzgerald]

In general, how bad is it to have a through-hole component with a pin length (as measured from the PCB surface) smaller than the PCB thickness?

I would like to mount a PCB flush to a substrate, so I cannot use pins sticking out. Unfortunately the component is only available as through hole. I did a check and I am able to hand solder the component with ease. Are there long-term issues to worry about?

[T3sl4co1l]

Such solder joints are suspect for production purposes.  They are hard to inspect (there's no fillet on the bottom, or it's hidden inside the barrel), and may have inferior strength (because there's no blob of solder holding them on the bottom, just a thin ring of copper).

I've done this before: for THT pin tails, and SMT components, on the bottom side, place the board against a squishy thermal pad.  This gives the heatsinking benefit of flush mounting, while maximizing usable board area for component placement, without compromising manufacturability.

But it's all a lot of noise on the wind if you have no process and no standard to work to.  One-offs?  Lab boards?  Do whatever you feel like.  If it works, it works...

Tim

[tszaboo]

Well, It conforms IPC-A-610D section 7.5.3 Which states, that the minimum length of the lead is: "End is discernible in the solder." On Figure 7-97 the end of the lead is flush with the pad.

[adih]

Is there a way, like adding a phase (countersink) to the hole from the bottom side (or counterbore) to make it fully comply with IPC 610?

[ar__systems]

Is there a way, like adding a phase (countersink) to the hole from the bottom side (or counterbore) to make it fully comply with IPC 610?

You can come with millions way to comply at the obscene cost.
Maybe just use thinner PCB...

[HHaase]

For the OP,   If you know the component is fully seated, and you have 100% hole fill,  I wouldn't worry in the least.

One thing to remember from the manufacturing world,  customer requirements overrule IPC standards.
IPC-610 is extremely useful to define build quality requirements between a manufacturer and a customer
It is not a legal requirement,  it's a trade organization standard.

Building for yourself, IPC is a good guideline to judge your work.   But it's up to you what standards apply for acceptability.

[ciccio]

Why not solder on the component side? I've done this with prototypes whose PCB was made, due to a mistake,  specular (they were single-side boards).
It was not a problem soldering on the component side (all pins were accessible).
You can trim the pins flush to under surface.
No problem with durability and reliability.

Best regards