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Counterbore raw board

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#43370

Counterbore raw board | 17 August, 2006

We are looking to possibly counterbore a coule of thru holes in one of our PCBs. We would counterbore the top side, and the only trace is coming out of the bottom side. The reason is to mount some LEDs flush with the board. They have some flash where the leads meet the body of the LED, so it won't sit flush to the board.

The holes are currently plated all the way thru.

Does anyone have any experience with this? Is there something in particular to look out for (i.e. min board thickness remaining, flaring, delamination, etc...)? Any help or advice would be appreciated.

Thanks, Mark

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#43380

Counterbore raw board | 17 August, 2006

It sounds more expensive just at face value than better LEDs, and potentially MUCH more exensive due to failures if there is any kind of stress on that weakened connection.

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Chunks

#43383

Counterbore raw board | 17 August, 2006

Well, you won't win any IPC awards for doing this. Another idea is to use a center punch to create the dimple you need. It wouls be quicker and you won't destroy the barrel like you will with a drill. Don't ask me how I know.

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#43388

Counterbore raw board | 17 August, 2006

Steve - The weakened condition was my concern, and that was why I was asking if anyone had any details on issues that may occur doing this. Do you know of any details behind the risks involved?

Qualifying a new LED will take a load of R&D resources (don't ask why, just take my word for it), so it was pretty much out of the question. However, if I could prove that a counterbore/countersink was reliable......that was the thought pattern.

Chunks - That is a nifty idea, but I don't think that will fly at the company I work for. I did have to think about it though...hmmmmmmmm...

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#43390

Counterbore raw board | 17 August, 2006

I don't have any data (haven't tried this), but it doesn't take much thought to see that determining the risks associated with simultaneously applying compressive and rotational forces to the end of the barrel, not to mention chewing up the copper, is going to require significant analysis.

I have to assume you've already had it out with the LED supplier. What is their rationale for providing you with parts with mold flash on the seating plane....is it in the spec.??

Finally, depending on the number of parts/board and your build quantities, it might be cheaper (and it certainly would be safer) to scrape/trim the LEDs than to mess with your boards.

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#43391

Counterbore raw board | 17 August, 2006

We use plastic standoffs that fit between the LED and the board. Live well, live long. For more than you wanted to know about standoffs: http://www.reedlink.com/ProductInfo~Productid~158255~ProductName~LED-Standoffs.html

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#43404

Counterbore raw board | 18 August, 2006

Thank for the feedback everyone.

The LED is designed to be soldered 2mm above the board, so that is their rational for allowing that much flash. And a spacer is not going to work because of the height limit of mating parts (I didn't design the boards...).

We were just trying to look for the easiest solution, but it doesn't sound like there is much information or data on counterboring a hole on a PCB. So.....we'll probably try to figure something else out.

Thanks all for the help.

Mark

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Chunks

#43409

Counterbore raw board | 18 August, 2006

Steve,

You almost got yout Man Card revoked for stating: "determining the risks associated with simultaneously applying compressive and rotational forces to the end of the barrel". Luckily you bounced back with "chewing up the copper". Just poking fun. Have great weekend everyone.

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Board House

#43411

Counterbore raw board | 18 August, 2006

Hi Mark,

Couterbore is possible in two way's during PCB Manufacturing.

Couterbore plated and non-plated. Meaning that the entire hole will either have to be Plated or Non-Plated.

Prefered Methode is Plated, to accomplish this your PCB house would drill all the holes and then take their panels to another drill which is cabable of controlled depth drilling and counterbore the hole on the selected sided needed. Once this is completed they run the panels through desmear and then would Shadow and then Plate.

When finshished you would have a Plated Counterbored hole which would allow you to have your LED flush.

Counterboring is an extra process but would not add a significant cost to the product.

Regards,

Board House

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#43413

Counterbore raw board | 18 August, 2006

blasted double post

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#43414

Counterbore raw board | 18 August, 2006

Not sneakin' anything past you, are we Chunks? :P

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Chunks

#43418

Counterbore raw board | 18 August, 2006

Does that make me a "Master" of post reading?

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