About etching with Ferric Chloride (FeCl3)

[kam]

Regarding the comment from user Skiwee in page PCB Etching Bath with Heater and Agitation

At 2 January 2012, 18:17:46 user Skiwee wrote:
    I like the setup, you seem to use it quite often.
    In the second video you agitate your etching solution. There\'s no need for that it\'s just copper sediment and waste from previous uses (it\'s best to hand this to your local hazardous waste management/company).
    The solution should have a dark orange/brown \"oily\" appearance.
    example image; http://upload.wikimedia.org/wikipedia/en/thumb/8/8c/Iron%28III%29_chloride.JPG/551px-Iron%28III%29_chloride.JPG
    for more information on chemicals a quick MSDS search on google goes a long way.

Well, as i was saying, this is the setup that i use for all my PCBs and never failed me, so i decided to make a bigger one. It will be a plexiglass parallelogram tank, about 35cm by 4 cm. The height will be more than 45cm, but i will not fill it to the top to avoid the mess of the FeCl3. Only the first 30-35 cm will have chemical. The total volume will be more than 4 and less than 5 liters, and i will be using one (or two) 500 watts heaters.

Skiwee's comment aroused two questions: First, Skiwee said that the FeCl needs no agitation. I will not totally disagree with this, he meant "air bubbles agitation". I use it about 2 years now, and from my experience i've noticed that if i move the PCB in and out from the chemical, the etching time is radically decreased. This could mean that the air bubbles are not that efficient, and that moving (with my and or with another mechanism) the PCB up and down is many times more effective than the bubbles. Am i right? Has anyone notice something similar???

Second question, Skiwee says that the solution should have an orange-brownish color. Indeed, this is the color of the solution BEFORE i agitate it. Because at the bottom, after having etched some PCBs, a yellow precipitate deposits. When the agitation starts, the solution becomes yellow, dark yellow. I've asked in the past some chemists to tell me what this precipitate is, but no one had worked with FeCl3 and therefore no one could answer. Strangely, i never tried to remove the yellow mud from the bottom to  test the solution, because every time that i wanted to use it, i was in a hurry to finish a PCB and never had time for tests whatsoever. Anyone knows what is this yellow thing? Is it good to remove it?

[Skiwee]

Wow, ~30x30cm PCB thats big. Do you really need that size?

sorry about the confusion, but what I should have said is you shouldn't stir the Ferric Chloride Solution.
The precipitate as you nicely put, is just waste from previous PCB's. Getting rid of it is like starting with a fresh batch and overall should speed up the process.
So it's always better to keep the solution "clean".
Borrowing an MSDS from http://www.inchem.com.ph/productpages/fecl3_msds.pdf
always under "Section 9"
Solubility in Water= Complete (this tells a chemist that it's completely absorbed by water/liquid and a solid is waste. {other sheets could say "Solubility = 100%})
I'm a bit flabergasted that chemists couldn't tell you.

As to agitating the solution while your etching.
Technically it's not needed indeed, but the practical benefits speed up the process by a lot. Even in a dish just rocking the solution back and forth is enough.
Little help from google the rocking method seems to take most people 15~20mins. Letting it sit, <lets just say long enough not to google it>.
So the air bubbles do the job much quicker then rocking and as a bonus you can let it sit (best of both worlds).

[kam]

hello Skiwee and thanks for following up.

So, now it makes scene. Yet again, from my experience i can tell that if the board is placed vertically in the solution (like in my etching tank), the process is many times faster if you continuously move the board up and down, taking out from the solution and dipping it in again. I do not know why, i can only suspect this: Stiring in general helps to remove the etched copper away from the board and let space for the fecl3 to etch some more underneath. I have noticed that the etching process is accomplished in layers, meaning that the copper is removed layer by layer (one thin layer each time). The bubbles agitate the board and the etched copper is removed, but the bubbles do not really cover the whole area of the board. Instead, of you remove the board, a whole layer of etched copper is removed every time. Again, i am not sure since i am not a chemist and know little about chemistry, but this is what i have observe during my etching jobs.

Regarding the precipitate, your answer helped a lot! Now i have to find a nice way to remove them from the solution. In my old tank that is easy, since after every use i remove the solution from the tank and store it in a glass bottle. But in my new tank, the solution will always remain in the tank. The tank will be the storage as well. -Probably the chemists that i asked were not aware that the fecl has solubility 100%. -
(((Sadly, i cannot open the attached document. It seems that my ISP IP is banned since i get 403 forbidden messages. Can you upload this document for me please?)))

Finally, regarding the new tank size: No i certainly do not need that big tank for big PCBs. But i want it for 2 reasons: First, i want the tank to have a lot of fecl solution so that the solution will last longer for more etching jobs, and second, i want the tank to be big so that i can etch multiple PCBs at once.

[Skiwee]

etch multiple PCBs at once.

Of course. *facepalm*

As to what happens chemically.
Doing some old homework again (yea.. only cause I got curious) and this is theoretical knowledge, as I've never actually tested samples myself. Always took it for granted.
But when the Ferric Chloride solution(FeCl3) comes in contact with the copper(Cu). There's a redox reaction (oxidizer) that creates FeCl2 + CuCl
That means that the precipitate is Copper Chloride.
It also means that the Ferric Chloride looses it's effectiveness in etching PCB's until the point where it will be unable to work.
Technically you could reactivate it but it's probably more expensive and time consuming to do, then just buying a new batch.

here's the/a MSDS (Material Safety Data Sheet) for basic compound of Ferric Chloride solutions on the market. (Always check your own product for the correct MSDS as there can be other chemicals added {usually too speed up the etching or allow for more copper absorption})
Think of this as the same as a data sheet for an electronic component.
Safety note for readers; I DON'T recommend making attempts of your own solution from dry FeCl3 with exception to professional chemists (in which case you already know this).
hehe no excuses for not knowing now

FERRIC CHLORIDE SOLUTION


1. === Product Identification ===
Synonyms: Iron (III) Chloride Solution
CAS No.: 7705-08-0
Molecular Weight: Not applicable to mixtures.
Chemical Formula: FeCl3 in H2O

2. === Composition/Information on Ingredients ===

     Ingredient
     CAS No 
     Percent 
     Hazardous 
   
     Ferric Chloride 
     7705-08-0
     35 - 45%
     Yes
   
     Water
     7732-18-5
     55 - 65% 
     No
   
3. === Hazards Identification ===
Emergency Overview
  --------------------------
  DANGER! CORROSIVE. CAUSES BURNS TO ANY AREA OF CONTACT. HARMFUL IF SWALLOWED OR INHALED. AFFECTS THE LIVER.

-----------------------------------------------------------------------------------------------------------
Health Rating: 2 - Moderate
Flammability Rating: 0 - None
Reactivity Rating: 2 - Moderate
Contact Rating: 3 - Severe (Corrosive)
Lab Protective Equip: GOGGLES &amp; SHIELD; LAB COAT &amp; APRON; VENT HOOD; PROPER GLOVES
Storage Color Code: White (Corrosive)
-----------------------------------------------------------------------------------------------------------

Potential Health Effects
----------------------------------

Inhalation:
Extremely destructive to tissues of the mucous membranes and upper respiratory tract. Symptoms may include burning sensation, coughing, wheezing, laryngitis, shortness of breath, headache, nausea and vomiting.
Ingestion:
Corrosive. Swallowing can cause severe burns of the mouth, throat, and stomach. Can cause sore throat, vomiting, diarrhea. Low systemic toxicity in small quantities but larger doses may cause systemic effects. Pink urine discoloration is a strong indicator of iron poisoning. Liver damage, coma and death may follow, sometimes delayed as long as three days.
Skin Contact:
Corrosive. Symptoms of redness, pain, and severe burn can occur.
Eye Contact:
Corrosive. Contact can cause blurred vision, redness, pain and severe tissue burns.
Chronic Exposure:
Repeated ingestion may cause liver damage. Prolonged exposure of the eyes may cause discoloration.
Aggravation of Pre-existing Conditions:
No information found.

4. ===First Aid Measures ===

Inhalation:
  Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention immediately.
Ingestion:
If swallowed, DO NOT INDUCE VOMITING. Give large quantities of water. Never give anything by mouth to an unconscious person. Get medical attention immediately.
Skin Contact:
Immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Get medical attention immediately. Wash clothing before reuse. Thoroughly clean shoes before reuse.
Eye Contact:
Immediately flush eyes with plenty of water for at least 15 minutes, lifting lower and upper eyelids occasionally. Get medical attention immediately.

5. === Fire Fighting Measures ===
Fire:
  Not considered to be a fire hazard. Irritating hydrogen chloride fumes may form in fire.
Explosion:
Not considered to be an explosion hazard.
Fire Extinguishing Media:
Water, dry chemical, foam or carbon dioxide. Do not allow water runoff to enter sewers or waterways.
Special Information:
In the event of a fire, wear full protective clothing and NIOSH-approved self-contained breathing apparatus with full facepiece operated in the pressure demand or other positive pressure mode.

6. === Accidental Release Measures ===
Ventilate area of leak or spill. Wear appropriate personal protective equipment as specified in Section 8. Isolate hazard area. Keep unnecessary and unprotected personnel from entering. Contain and recover liquid when possible. Collect liquid in an appropriate container or absorb with an inert material (e. g., vermiculite, dry sand, earth), and place in a chemical waste container. Do not use combustible materials, such as saw dust. Do not flush to sewer! US Regulations (CERCLA) require reporting spills and releases to soil, water and air in excess of reportable quantities. The toll free number for the US Coast Guard National Response Center is (800) 424-8802.


7. === Handling and Storage ===
Keep in a tightly closed container, stored in a cool, dry, ventilated area. Protect against physical damage. Isolate from incompatible substances. Containers of this material are hazardous when empty since they retain product residues; observe all warnings for the product.

8. === Exposure Controls /Personal Protection ===
Airborne Exposure Limits:
  -ACGIH Threshold Limit Value (TLV):
  1 mg/m3 (TWA) soluble iron salt as Fe
Ventilation System:
A system of local and/or general exhaust is recommended to keep employee exposures below the Airborne Exposure Limits. Local exhaust ventilation is generally preferred because it can control the emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent edition, for details.
Personal Respirators (NIOSH Approved):
If the exposure limit is exceeded and engineering controls are not feasible, a full facepiece particulate respirator (NIOSH type N100 filters) may be worn for up to 50 times the exposure limit or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. If oil particles (e.g. lubricants, cutting fluids. glycerine, etc.) are present, use a NIOSH type R or P filter. For emergencies or instances where the exposure levels are not known, use a full-facepiece positive-pressure, air-supplied respirator. WARNING: Air-purifying respirators do not protect workers in oxygen-deficient atmospheres.
Skin Protection:
Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as appropriate, to prevent skin contact.
Eye Protection:
Use chemical safety goggles and/or a full face shield where splashing is possible. Maintain eye wash fountain and quick-drench facilities in work area.

9. === Physical/Chemical Properties ===
Appearance:
  Orange to brown liquid.
  Odor:
  Acid odor.
  Solubility:
  Complete (100%)
  Specific Gravity:
  1.40
  pH:
  <1 (apparent)
  1.82 (1% solution)
  % Volatiles by volume @ 21C (70F):
55-65
Boiling Point:
230C (446F)
Melting Point:
No information found.
Vapor Density (Air=1):
No information found.
Vapor Pressure (mm Hg):
No information found.
Evaporation Rate (BuAc=1):
  No information found.
  Flash Point:
  Not applicable

10. === Stability and Reactivity Data ===
Stability:
  Stable under ordinary conditions of use and storage.
  Hazardous Decomposition Products:
  May produce hydrogen chloride.
  Hazardous Polymerization:
  This substance does not polymerize.
  Incompatibilities:
  Metals, allyl chloride, sodium, potassium.
  Conditions to Avoid:
Incompatibles.

11. === Toxicological Information ===

Oral rat LD50: 450 mg/kg (anhydrous); investigated as a mutagen, reproductive effector.

Code: [Select]

  --------\Cancer Lists\------------------------------------------------------
                                         ---NTP Carcinogen---
  Ingredient                             Known    Anticipated    IARC Category
  ------------------------------------   -----    -----------    -------------
  Ferric Chloride (7705-08-0)             No          No            None
  Water (7732-18-5)                       No          No            None
&nbsp;

12. === Ecological Information ===
Environmental Fate:
  No information found.
  Environmental Toxicity:
No information found.

13. === Disposal Considerations ===
Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste facility. Although not a listed RCRA hazardous waste, this material may exhibit one or more characteristics of a hazardous waste and require appropriate analysis to determine specific disposal requirements. Processing, use or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and local requirements.


14. === MSDS Transport Information ===
Ferric Chloride, Solution, 8, UN 2583, PG III
  Label Required: Corrosive

15. === Regulatory Information ===

Code: [Select]

--------\Chemical Inventory Status - Part 1\---------------------------------
  Ingredient                                       TSCA  EC   Japan  Australia
  -----------------------------------------------  ----  ---  -----  ---------
  Ferric Chloride (7705-08-0)                       Yes  Yes   Yes      Yes                                     
  Water (7732-18-5)                                 Yes  Yes   Yes      Yes                                     
 
  --------\Chemical Inventory Status - Part 2\---------------------------------
                                                          --Canada--
  Ingredient                                       Korea  DSL   NDSL  Phil.
  -----------------------------------------------  -----  ---   ----  -----
  Ferric Chloride (7705-08-0)                       Yes   Yes   No     Yes       
  Water (7732-18-5)                                 Yes   Yes   No     Yes
 
  --------\Federal, State & International Regulations - Part 1\----------------
                                             -SARA 302-    ------SARA 313------
  Ingredient                                 RQ    TPQ     List  Chemical Catg.
  -----------------------------------------  ---   -----   ----  --------------
  Ferric Chloride (7705-08-0)                No    No      No         No
  Water (7732-18-5)                          No    No      No         No
 
  --------\Federal, State & International Regulations - Part 2\----------------
                                                        -RCRA-    -TSCA-
  Ingredient                                 CERCLA     261.33     8(d)
  -----------------------------------------  ------     ------    ------
  Ferric Chloride (7705-08-0)                1000       No         No     
  Water (7732-18-5)                          No         No         No                                                               
 
Chemical Weapons Convention:  No     TSCA 12(b):  No     CDTA:  No
SARA 311/312:  Acute: Yes      Chronic: Yes  Fire: No  Pressure: No
Reactivity: No          (Mixture / Liquid)


    Australian Hazchem Code: None allocated.
    Poison Schedule: None allocated.
    WHMIS:
    This MSDS has been prepared according to the hazard criteria of the Controlled Products Regulations (CPR) and the MSDS contains all of the information required by the CPR.

&nbsp;

16. === Other Information ===
NFPA Ratings: Health: 3 Flammability: 0 Reactivity: 0
  Label Hazard Warning:
  DANGER! CORROSIVE. CAUSES BURNS TO ANY AREA OF CONTACT. HARMFUL IF SWALLOWED OR INHALED. AFFECTS THE LIVER.
Label Precautions:
Do not get in eyes, on skin, or on clothing.
Do not breathe mist.
Keep container closed.
Use only with adequate ventilation.
Wash thoroughly after handling.
Label First Aid:
In case of contact, immediately flush eyes or skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. If swallowed, DO NOT INDUCE VOMITING. Give large quantities of water. Never give anything by mouth to an unconscious person. In all cases get medical attention immediately.
Product Use:
Laboratory Reagent.


High Valley Products, Inc. provides the information contained herein in good faith but makes no representation as to its comprehensiveness or accuracy. This document is intended only as a guide to the appropriate precautionary handling of the material by a properly trained person using this product. Individuals receiving the information must exercise their independent judgment in determining its appropriateness for a particular purpose.


HIGH VALLEY PRODUCTS, INC. MAKES NO REPRESENTATIONS OR WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO THE INFORMATION SET FORTH HEREIN OR THE PRODUCT TO WHICH THE INFORMATION REFERS. ACCORDINGLY, HIGH VALLEY PRODUCTS, INC. WILL NOT BE
  RESPONSIBLE FOR DAMAGES RESULTING FROM USE OF OR RELIANCE UPON THIS INFORMATION.
Revision Date
9-21-2006

*quick edit* On a side note thinking about it, for even faster etching with FeCl3 spraying would work as well. I even found a european company that manufactures them they say it etches within 90 seconds. Be extremely careful if you ever decide to DIY. but would defiantly be cool.

[kam]

Thank you for taking time posting the MSDS. As a matter of fact, this is the first time that i see such a document! It seems that you have some good knowledge in chemistry. I will make one more question. In paragraph 10 of the MSDS (Stability and Reactivity Data) it states:

Incompatibilities:
Metals[.....]

Does this includes also stainless steel alloy? I was searching on ebay and found some nice stainless steel 500W heaters. I plan to use glass heaters, but if stainless steel is not affected by the chemical, then i will prefer to use them instead. Generally, are there documents (like the MSDS which i was completely unaware of) that have more detailed info for incompatibilities? Do you happen to know?

[Skiwee]

Sorry, if any metal comes in contact with ferric chloride it's going to corrode and contaminate it. The vapor is also quite corrosive.
The only exception is titanium (I always used titanium rods when anodizing aluminum). Titanium creates a protective oxidized layer that lasts, stainless steel has a similar reaction but only in water & air.

As to other MSDS documents, every chemical manufacturer is required to have this data available with every hazardous product they sell/produce. There are law's in place that standardize it. It's mainly information meant for the people that need to know how to handle it and usually there are a handful of them online.

[kam]

ok i see. thank you for your time.