Lead Cutting Standard for Electronic Components

Are you starting a new business?

"What the standard is for lead cutting for all electronics components"

Ask your customers what they want you to trim to.

"If we cut the leads till the edge of the solder joint is there any reliability issue with solder joints?"

Ask your customer. Where are you?

Replying to you: lynlynch and redfred

Hmmmm I'm not sure about this: if I was the customer: and my PCB manufacturer started asking me how make PCBs to ensure good solder joints, I think I'd start looking round for another subcontractor.

I suppose there are ways of asking diplomatically, but, I think the OP should start with a standard approach (backed up by industry standards) at the very least.

Keep the lead as short as possible such that the component is as close as possible to the surface of the PCB.

"If we cut the leads till the edge of the solder joint is there any reliability issue with solder joints?" I don't foresee any reliability issue as long as there is no damage to the contacts.

Cheers,

ethobil

Hello guest (consider registering please),

I imagine you are talking about the non-component side lead cutting, after the assembly has been soldered?

We build hundreds of assemblies per day here where I work, and quite some time ago, we did away with nearly ALL lead cutting after the assembly was built. Part of the reason was stress on the assemblers hands (carpal-tunnel syndrome is a problem), but the other reason was that it CAN stress the solder joint that is being trimmed, the closer you attempt to trim, the more likely you are to stress the joint. If we have components that have lead-lengths that are going to be a problem, we try to do the trimming BEFORE they are inserted and soldered into the assemblies. One more issue with post-assembly lead trim, it leaves the base-metal of the component lead exposed to the air, something that can cause problems over time, especially for assemblies that are exposed to harsh environments.

If you can avoid post-assembly trim operations, you will be better off all the way around.

Tom

Thank you

it CAN stress the solder joint that is being trimmed

it leaves the base-metal of the component lead exposed

If you can avoid post-assembly trim operations, you will be better off all the way around

"Solder, cut, solder" addresses these problems.

Original Poster, Are you manually cutting or using a machine?

Are you flow soldering? (I guess that solder cut solder is out of the question if you're manually soldering).

You make some good points that i have never ever considered before. Many thanks, I will follow your example in the future.

There is an IPC standard for this.

If you are a manufacturer of electronic circuit boards then you should avail yourself of these standards. Ensure that all your production and engineering staff are suitably trained and certified. Ensure that they apply those standards to their work practices.

However as a rule of thumb the leads should not be long enough to contact adjacent pads should they be bent over, either on purpose or by mishandling.

This is found in any book on PCb assembly, so you need to read up on your subject if you are looking at volume. Have a look inside your pc or hi fi unit for examples.

Leads should go through the board and soldered, leads cut off below the solder ball.

Leads should be bent to keep the component flat and close to the board, bends should be such that there is no tension on the component, it should not bow.

regards

As the variety of answers have stated and implied, there are standards but not everyone follows them all the time. The reasons for varying from these standards span the gamut from anticipated board environment to worker laziness. (I've been there and done that.)

But as another answer states, your customer's choice is paramount. (I guess I should go back and give him a GA.) The standard is whatever the customer wants.