Previous in Forum: Underwater Data Communications   Next in Forum: NE5554U Data Sheet
Close
Close
Close
22 comments
Anonymous Poster

Scratches on Printed Circuit Boards (PCBs)

10/13/2009 11:48 PM

we are facing minor scratches problem on the PCB and our customer has concern on the reliability of the PCB.

what is the effect minor scratches on the PCB with respect to reliability of the PCB.

the thickness of the solder mask is more than 15 micron on the scratches area. scratches are in area of both on the copper and epoxy area.

can some body explain me how scratches effects on the reliability of PCB in long run

Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#1

Re: Scratches on the Printed circuit boards

10/14/2009 1:26 AM

Asian circuit board companies don't seem to understand the aesthetic = quality connection that exists in the Western world. I know many a US company that has refused Asian boards just because of their looks.

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Reply
Guru
New Zealand - Member - Kiwi Popular Science - Weaponology - New Member Engineering Fields - Power Engineering - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: Auckland, New Zealand
Posts: 8778
Good Answers: 376
#3
In reply to #1

Re: Scratches on the Printed circuit boards

10/14/2009 3:07 PM

You get what you pay for anywhere in the world, some management types cannot quite seem to grasp the basics of commercial reality.

__________________
jack of all trades
Reply Off Topic (Score 5)
Guru
Hobbies - Fishing - Old Salt Hobbies - CNC - New Member United States - US - Statue of Liberty - New Member

Join Date: Mar 2007
Location: Rosedale, Maryland USA
Posts: 5198
Good Answers: 266
#2

Re: Scratches on the Printed circuit boards

10/14/2009 9:17 AM

The epoxy was to encapsulate the circuits and to protect them. If it is scratched off it no longer provides that protection. The environment in which the board is placed may degrade the copper. Scratches across the copper conductor may cause a resistance depending on the amount of current. This resistance will cause heat stressing the copper so that it may fail.

__________________
Life is not a journey to the grave with the intention of arriving in a pretty, pristine body but rather to come sliding in sideways, all used up and exclaiming, "Wow, what a ride!"
Reply
Guru

Join Date: Oct 2008
Posts: 42294
Good Answers: 1662
#4

Re: Scratches on the Printed circuit boards

10/14/2009 4:18 PM

we are facing minor scratches problem on the PCB and our customer has concern on the reliability of the PCB. Define the "scratch" with regard to the reduction of conductor cross section that is caused by it. What does the spec say?

what is the effect minor scratches on the PCB with respect to reliability of the PCB. Depends on frequency, temperature/environmental conditions. What does the spec say?

the thickness of the solder mask is more than 15 micron on the scratches area. scratches are in area of both on the copper and epoxy area. What do the scratches look like? Depth, width, length? What does the spec say?

can some body explain me how scratches effects on the reliability of PCB in long run Maybe not at all, maybe total failure. What does the spec say?

If you don't have a spec, never mind.

Reply
2
Guru

Join Date: Oct 2008
Location: Deepest Darkest Rutherford Oz
Posts: 951
Good Answers: 145
#5

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 1:52 AM

The question you should be asking is where, how and why are the scratches getting onto the boards in the first place.

Review your work procedures and practices.

Ascertain the cause of the problem.

Remedy the cause with an appropriate solution by, amending the poor procedures and or work practices as evidenced by customer dissatisfaction of your products.

Free consultation is now concluded.

__________________
There are two reasons for a man to do a thing, One that sounds good, and the real one...
Reply Good Answer (Score 2)
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 5317
Good Answers: 290
#6
In reply to #5

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 3:32 AM

GA:-

Figuring out how to prevent the scratches is going to be much easier than trying to "quantify" how bad they are.

__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#7

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 4:25 AM

The PCBs are being mishandled at some point, that should be identified and the problem fixed.

For PCBs already made and tested, mask off any contacts and sockets and spray with a quality lacquer (2 component?) on both sides. This will make sure that no moisture can get into the board and also make it look far better.....its not a way to go except as a last resort to my mind.....if labour is cheap get people with paint brushes and solder resist to touch up the resist scratches.....

Make sure that tested boards are not given a problem because of the paint job, that would be a disaster.....re-testing is probably not an option, but it could be if the re-workers do a shoddy job!!!

As already pointed out, this scratching should never happen, "1 ounce of prevention is worth a Pound of cure!"

__________________
"What others say about you reveals more about them, than it does you." Anon.
Reply
Active Contributor

Join Date: May 2009
Location: Western PA, US
Posts: 22
#8

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 6:40 AM

First I would find out what is causing the scratches and correct the manufacturing process. This is your root problem.

Next I would find a training course in IPC610 and begin development of a quality control program with standards and procedures.

As for boards already placed in the field there are two things you need to do. First, ascertain whether or not the "scratches" reduce the thickness of your traces or in any way lift, bend or break traces or pads. These scratches can be examined under a microscope to gage depth and thickness for deeper analysis. This is all assuming the boards are un-populated to this point.

If the boards are found to be functional after inspection of the traces then appearances can be corrected and the scratches covered by a conformal coating. This should be done after population if at all possible or the masking must be perfect if you are doing it with a bare board.

I cannot fathom someone manufacturing a circuit board without already having IPC standards in place that clearly dictate what is acceptable and what is not. Even appearance is covered quite well by these standards.

Rick Stanley

__________________
Very funny Scotty, now beam down my clothes!
Reply
Associate

Join Date: Dec 2005
Location: South Central Wisconsin
Posts: 35
Good Answers: 3
#9

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 8:17 AM

<can some body explain me how scratches effects on the reliability of PCB in long run>

In order to determine long term effects, you will have to perform life cycle testing on the products (preferably under operating conditions). Tests that come to mind are thermocycling, HHA (heat and humid atmosphere) and HDA (heat and dry atmosphere).

__________________
That which is watched, is optimized.........
Reply
Power-User

Join Date: Mar 2008
Location: MA 01864, USA
Posts: 453
Good Answers: 7
#10

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 8:56 AM

When we see scratch on epoxy we make area susceptable to mositure absorption which changes electrical properties and breakdown voltage.

If there is small scratch in copper then we create electrical field high enough we will have electrical failure

This is hard to explain asian manufacturers since they have no concept of the board quality and particularly poards came from China

The common failure with scractch are break down dielectric voltage decrease and hence non optimum performance and shorter life because of epoxy scratch

With copper crack localized heating around crack and circuit break down during extend use

__________________
Masyood
Reply
2
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15136
Good Answers: 937
#11

Re: Scratches on Printed Circuit Boards (PCBs)

10/15/2009 10:40 AM

Who cares what effect these scratches have on the reliability of the circuit board? You produce a product with no pride in your work. Instead of attempting to find the root cause of these visible imperfections in your craftsmanship, you still want to palm them off onto your customer. Had you demonstrated that you've already discovered the root cause of these problems, mitigated the problem and proven that new boards or better yet the remainder of this batch of circuit boards were unscratched; your integrity may have remained intact. Now if your customer stated a standard that stated an unscratched board you will be obligated by contract to fabricate replacement clean boards. But if you volunteer to replace these boards or you have to be coerced by contract stipulation to replace these boards don't expect this customer to use your services again.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply Good Answer (Score 2)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#12
In reply to #11

Re: Scratches on Printed Circuit Boards (PCBs)

10/16/2009 12:45 AM

Very true......

__________________
"What others say about you reveals more about them, than it does you." Anon.
Reply
Guru
Hobbies - Musician - Tube Amps Only Please!

Join Date: Apr 2009
Location: Los Angeles, California USA
Posts: 554
Good Answers: 1
#13

Re: Scratches on Printed Circuit Boards (PCBs)

10/20/2009 2:48 AM

A scratch on the trace would be a big concern if it causes an open (big scratch) or causes the line to have very little copper left. The question I would ask is how are these scratches occurring? I have hears of PCBs with cracked lines over time or stress cracks.

__________________
Regards, Maveric Manic - 'Knowledge is Power and Wisdom is knowing how to use it'
Reply
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#16
In reply to #13

Re: Scratches on Printed Circuit Boards (PCBs)

10/20/2009 10:34 PM

The boards from Asia are completely tested, and prove good in every way. So there's no worry, but some customers won't accept them. It basically an aesthetic thing.

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Reply
2
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#17
In reply to #16

Re: Scratches on Printed Circuit Boards (PCBs)

10/21/2009 4:45 AM

Vermin my friend, scratches are probably more than 90% aesthetic as you say, but you have to remember that it demonstrates to the customer, the quality of the work, or better said, the lack of.....in a rather clear manner.

Scratches show that the people that make them are slap-dash in their work practises. Having worked in production in the USA and Porto Rico for several months, I cannot even imagine how yours get scratched in the first place.

Our boards were placed with sheet of paper between them in plastic boxes before being shipped to the automatic component placer machines. AS I have no recollection of ever seeing a scratched PCB, I do not know what actions would have been taken if one had been seen AND WE WERE OUR OWN CUSTOMER AT THAT POINT! We sold only fully finished units that customers never saw the inside of !!!

Also, as several posters have already mentioned, there is the possibility of failure depending upon where and how deep the scratches are.....scratches can in slightly damp conditions, allow the copper to corrode if exposed, thin lands can be eaten away.

I personally, in MANY years of working in the computer industry, electronics industry and my own personal domestic electronics, have seldom ever seen a scratched PCB, in fact I have no recollection of ever seeing one, ever.

So it is no small wonder, that your customer is feeling unsafe.....I would too. The only "FIX" is to produce boards without any scratches......and no other failures either!!!

Or you stand a good chance to lose the customer completely....with all its consequences.......

I am still a Hobby Electronics person and from time to time I buy or have made PCBs, or buy and build kits. Never have I seen a scratched PCB.......

I personally believe you need to change your "take" on this point.....

This post is intended to help not to hinder, I hope you receive it in the manner intended.

Have a great day.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Reply Good Answer (Score 2)
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15136
Good Answers: 937
#18
In reply to #17

Re: Scratches on Printed Circuit Boards (PCBs)

10/21/2009 9:22 AM

A nicely expanded response Andy. Well said and another GA from me.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#19
In reply to #18

Re: Scratches on Printed Circuit Boards (PCBs)

10/21/2009 12:05 PM

Thank you kind sir....

__________________
"What others say about you reveals more about them, than it does you." Anon.
Reply Off Topic (Score 5)
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#20
In reply to #17

Re: Scratches on Printed Circuit Boards (PCBs)

10/21/2009 10:39 PM

I think you misunderstood me. I'm not saying that scratched PCBs are OK, I'm saying that some Asian PCB houses do not understand Westerner's reluctance to use/accept the boards they produce.

My guess is that they get a deal on scuffed and scratch PCB stock and try to use it to reduce their costs.

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15136
Good Answers: 937
#21
In reply to #20

Re: Scratches on Printed Circuit Boards (PCBs)

10/21/2009 11:59 PM

I understood and I suspect Andy did, too. You weren't advocating the use of these boards, you were explaining why some PCB houses still use damaged boards. The difference between an excuse and an explanation.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#22
In reply to #21

Re: Scratches on Printed Circuit Boards (PCBs)

10/22/2009 12:24 AM

And the concept that some Asian PCB houses think it's just a matter of those fussy Westerner's sense of aesthetics... They'd (the Asian manufactures) would use the boards in a heartbeat, and let the chip fall where they may.

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Reply
Guru

Join Date: Oct 2008
Location: Deepest Darkest Rutherford Oz
Posts: 951
Good Answers: 145
#14

Re: Scratches on Printed Circuit Boards (PCBs)

10/20/2009 3:43 PM

Any process damage to the circuit board is a cause of concern, whether it be scratches on tracks or the skin of the lamination.

Depending on the on the operational intent of the circuit board, it will (not might) lead to failure of the device.

The IPC standard lists 3 classes of device,

Class 1 which is essentially domestic devices where it needs to work out of the box but not forever.

Class 2 which is general industrial /commercial. This is much more stringent in quality applied to the assembly of the device with the intention that the device will function for a minimum service life.

Class 3 This is top shelf Aerospace, Medical, Mining equipment where it is absolutely imperative that the device functions to spec for an extended service life.

Then you have the new class.

Class 1C (China) It might work out of the box if your lucky but don't expect it to last longer than the warranty period if it has one. But hey what do you want for $4.99.

The biggest trouble is production standards are now decided by bean counters(accountants) who know the cost of everything but the value of nothing.

You have a process problem in your factory, your client expected at least Class 1 maybe Class 2 for their product. However you presented them with Class 1C, which is not acceptable.

You have the answer to your problem if not the question you asked.

__________________
There are two reasons for a man to do a thing, One that sounds good, and the real one...
Reply
Power-User

Join Date: Mar 2008
Location: MA 01864, USA
Posts: 453
Good Answers: 7
#15
In reply to #14

Re: Scratches on Printed Circuit Boards (PCBs)

10/20/2009 4:45 PM

I am 100 percent in agreement. It is old saying what you pay what you get. If you paid chinese quality product then you do not expect any life out of it.

China have come long way but they have to go far long than any third world country. They were good in copying and are still good in doing that and getting world attention by making things which does not cost labor expense.

__________________
Masyood
Reply
Reply to Forum Thread 22 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Copy to Clipboard

Users who posted comments:

Andy Germany (4); jack of all trades (1); lyn (1); Masyood (2); maveric_manic (1); MrM (1); ozzb (1); Randall (1); redfred (3); rstanley3105 (1); Tobugrynbak (2); vermin (4)

Previous in Forum: Underwater Data Communications   Next in Forum: NE5554U Data Sheet

Advertisement