CR4 - The Engineer's Place for News and Discussion ®


Previous in Forum: Toluene Gravure Formulation   Next in Forum: Nicotine and Niacin
Close
Close
Close
12 comments
Participant

Join Date: Oct 2011
Posts: 3

White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 5:32 AM

Hi, Pls suggest some alternate materials for WHITE RESIDUE FORMATION ON PRINTED CIRCUIT BOARD ASSEMBLIES

Currently we are using Eraser for cleaning the IC surface

Regards

Dinesh

__________________
ardinesh07@gmail.com
Register to 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".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 25749
Good Answers: 677
#1

Re: WHITE RESIDUE FORMATION ON PRINTED CIRCUIT BOARD ASSEMBLIES

07/15/2016 5:43 AM

The question is not clear. Are alternative white deposit materials (e.g. breadcrumbs/chalk/titanium dioxide/gloss paint) required to be coated on the circuit boards after they have ben cleaned with the eraser, or is the method of cleaning unsatisfactory in some way? If the cleaning is unsatisfactory, some idea of the nature and extent of the white deposits would accelerate the journey towards satisfactory alternatives. Please advise.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
Hobbies - CNC - New Member Hobbies - DIY Welding - New Member Engineering Fields - Electromechanical Engineering - New Member

Join Date: Aug 2007
Posts: 17397
Good Answers: 302
#2

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 9:19 AM

White residue formation on printed circuit boards?....... Ok, I'll take a stab in the dark at it.

The answer is.......

Use rosin core solder instead of acid core solder.

__________________
phoenix911
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#3

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 9:54 AM

Run them through a dish washer using HOT soapy water, then rinse in isopropyl alcohol and blow dry.

Register to Reply Score 1 for Good Answer
Guru
Australia - Member - New Member

Join Date: Feb 2008
Location: Australia
Posts: 1694
Good Answers: 198
#4

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 9:59 AM

What is your soldering method??

If wire solder, then acid as previously indicated. (One of multiple)

If wavesoldering, then possibly dross on the wave, or exess flux solids. (Two of multiple)

If Surface mount "reflow", then incomplete flux activation. (Too fast through pre-heater zone, temps too low .....)

If not immediately obvious, then oxidation of the solder in humid conditions.

Note that I am presuming that these are already soldered boards/panels. If the "white" residue is there before soldering, then another set of options, like double sided reflow panels where the organic protective layer is cooked off both sides on first pass, necessitating short delays to second side pass.

__________________
Just an Engineer from the land down under.
Register to Reply Score 1 for Good Answer
Participant

Join Date: Oct 2011
Posts: 3
#11
In reply to #4

Re: White Residue Formation On Printed Circuit Board Assemblies

07/18/2016 2:48 AM

Hi,

Thanks your reply

Right now we are doing the soldering through Reflow. Board Materials is Silicon Wafer. At the time reflow soldering there is no issue in BGA at the bottom side, In top side(Black) we are facing white formation

We already used Dishwasher, Eraser, IPA and Bio Act SC25. But there is no improvement using these chemicals

Pls advice any other alternate materials or method to avoid this white formation

__________________
ardinesh07@gmail.com
Register to Reply
2
Guru
Australia - Member - New Member

Join Date: Feb 2008
Location: Australia
Posts: 1694
Good Answers: 198
#12
In reply to #11

Re: White Residue Formation On Printed Circuit Board Assemblies

07/18/2016 6:33 AM

I suggest that you run a board/panel through with no solder paste or SMT to see whether it's present on"virgin" boards as received.

Also could you please clarify the following.

  • Is the white residue only noticed on the solder lands?
  • Is there any residue observed on solder mask?

I'm thinking that any one of the following is happening.

  • Misprint boards (solder paste) are being washed in contaminated bath.
  • First pass (BGA side) is baking off the organic protective layer on second (Back) side and then environment is oxidising that surface.(Would show only on solder lands and other "protected" surfaces.
  • Solder paste screen bottom side is contaminated and stamping the contaminant onto boards. (Bad wash of screens) If this is the case, then you would see a similar pattern (on the panels) in each batch, but different next batch.
  • Solder paste screen bottom side contaminated. (I know we had auto wipe every 5 prints.) Machine adjustment (if automatic) or operator dilligence if manual.
  • Manual handling or interleaf transferring contaminant onto board surface.
  • Panel "top" is cold in reflow and fluxes are re-condensing on that surface. (Insufficeint pre-heat, insufficient ventilation.)
  • Reflow oven is contaminated and dropping "dust" (But this would usually clean off easily.)

From what you have described and the cleaning difficulty, I'm almost betting that it's solder paste that has somehow gotten onto that surface and been cooked in place.

Getting the process ABSOLUTELY RIGHT will eliminate the need for REWORK and give you consistent product without the risk of the additional work you are doing.

Yes, I have used board and screen washing equipment, yes I have cleaned and inspected solder screens and a few other bits.

We ran JUKI machines 24/7, 365 days per year. Only a small shop with one line putting down around 5 component per second. 0603 was our smallest. Double sided boards, some through hole LEDs (50,000 per day)

__________________
Just an Engineer from the land down under.
Register to Reply Good Answer (Score 2)
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 3948
Good Answers: 217
#5

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 10:02 AM
__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39041
Good Answers: 1533
#6
In reply to #5

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 11:37 AM

If I were a betting man, I'd wager that OP wants free solutions to his quandary, not necessarily the best ones.

Register to Reply
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 3948
Good Answers: 217
#7
In reply to #6

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 11:45 AM

You're right of course.

The simple answer is to wash and dry them: the search was to allay his fears about submerging them in water.

__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Register to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 17200
Good Answers: 978
#8

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 11:48 AM

We used to run them through the dishwasher....

__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Guru
United States - Member - Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - RC Aircraft - New Member Engineering Fields - Aerospace Engineering - New Member

Join Date: May 2009
Location: On the road, USA
Posts: 2055
Good Answers: 65
#9

Re: White Residue Formation On Printed Circuit Board Assemblies

07/15/2016 6:14 PM

"Pls suggest some alternate materials for WHITE RESIDUE FORMATION ON PRINTED CIRCUIT BOARD ASSEMBLIES"

You need to ask the customer what color they prefer, red, yellow, blue, green or black? Once they decide on what color they like, then we I can provide you with an alternative material

And please disengage your CAP Lock, nobody like being shouted at. No matter how frustrated you are

__________________
Confucius once said, “ Ability will never catch up with the demand for it".
Register to 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: 17812
Good Answers: 194
#10

Re: White Residue Formation On Printed Circuit Board Assemblies

07/16/2016 7:21 AM

Good cleaning after production.

Some coating that protects the PCB and allows soldering.

After soldering, cleaning and testing, then protect the PCB correctly again.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Register to Reply 12 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".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Andy Germany (1); ardinesh07 (1); dj95401 (1); Just an Engineer (2); lyn (2); phoenix911 (1); PWSlack (1); Randall (2); SolarEagle (1)

Previous in Forum: Toluene Gravure Formulation   Next in Forum: Nicotine and Niacin

Advertisement