1. OMG Fidelity ELECTROLESS NICKEL IMMERSION GOLD

2. Electroless Nickel Plate
Typical PCB Process
Acid Clean 
Microetch
Palladium Activate
Electroless Nickel Plate
Immersion Gold Plate

3. Metal Finishing EN Formulations
Low Phos.
Chosen for solderablity.
Heavy metal stab.
Difficult to control.
No longer in use for PCB processing.
Mid Phos.
Great general purpose plating.
Not designed for PCB processing.
Can skip plate.
Still used for PCB processing.

4. 9026M Electroless Nickel Specifically formulated for circuit boards
Consistent deposition rate over a wide range of bath loading.
No minimum work load! No Dummy panels!
Self pH regulating.
1 to 1 replenishment. Easy to control.
No bail-out, far less to waste treat.
Works well with many types of soldermasks.

5. Electroless Ni Bath is Key to this Process
Many problems seen in the industry come from the electroless nickel bath.
Two main process problems: Skip and Stray plating along with the main performance problem identified recently ; “Black Pad”
Although other processes can influence these problems, most of the control is in the electroless nickel bath formulation and operation.

6. Electroless Nickel Bath Ingredients
REDUCING AGENT
COMPLEXERS
ADDITIVES
STABILIZERS

7. EN Bath Additives Effect on PCB’s
Key to Soldermask compatibility.
Controls phosphorus content and deposit characteristics/performance.
Determines operating temperature and plating rate.
Determines work load range.
Prevents bath decomposition from normal activator drag-in.

8. Control of replenishment is essential to
Type and Control of Additives are Critical
Control of replenishment is essential to
proper electroless nickel operation as well
as the properties of the deposit.
Over stabilized >> Skip (areas without
EN)and “black Pad” (areas with EN).
Under stabilized >> Stray (EN creeps on to
laminate or soldermask)
Consumption of Additives may not be
equal to that of nickel and hypo. This will
create an “out of balance” condition.

9. Effect of Additive Balance
For many years, certain compounds
(typically two or three types) are used
as additives in electroless nickel
formulations at PPM levels. They must
be in balance to get an optimal nickel
deposit. Their balance or “ratio” has a
large effect on the deposit
characteristics.

10. “Out of Balance” Deposit effects
Low type 1 additive and/or high type 2
Rough deposits
Tank plate-out
Background plating
Black pad and possibly skip plate
Low type 2 and/or high type 1
Edge pull back
Low plating rate

11. Additive Levels
When the additives are in balance, the deposit may appear normal. Higher than normal levels can cause problems that are not easy to detect.
Assembly defects are usually detected too late.
The goal is to eliminate the root cause of unseen defects rather than try to precisely control the levels.

12. Real World Processing- What Happens In Your Tank
Continued large replenishments can aggravate these higher than normal levels.

13. Cyanide Strip Test
Indicates corrosion resistance of the nickel deposit.
Does not show the difference between nickel oxide and bath by-products. Nickel oxide is normal and will not be a problem for assembly as long as the gold is present and of sufficient thickness.
Strip time/temp and stripper bath composition have large effects on the appearance of the nickel.

14. “Black Pad”? Hard to tell by eye!
“A” “H” “M”
Photos taken after immersion gold was cyanide stripped.
This shows the boundary layer between the bulk EN and the gold. “H” has a phosphorus content of 12%. “A” and “M” both have a phosphorus content of 7%, with different stabilizers. High phos nickel (“H”) has the highest corrosion resistance to the stripping solution. Slight darkening from nickel oxide (“M”) should not be confused with unwanted bath compounds.
Only “A” has detectable amount of Additive byproducts.

15. “Hypercorrosion” = Much Confusion
Immersion Gold bath corrosion has been confused with as plated electroless nickel deposit structure.
Until now, little work has been done on the effects of the EN additives on both composition and structure.

16. Structure Vs Composition
Test sample plated at both higher than normal pH and temperature
This type of nickel structure has passed all assembly criteria. Only extremely rough deposits where nickel to nickel failure is likely will cause assembly rejects.

17. What Is “Black Pad”? Whatever the cause, everyone will agree,
assembly rejects are the major concern.
What is the cause?
How can a theory be proven?
Analysis of failed parts is a requirement of any defect investigation.
Once a mechanism is suspected, it must be tested by assembly.

18. Assembly Performance Testing
Performed at independent test lab
#1. Circuit patterns prone to “black
pad” are selected for test.
#2. Patterns are plated with two
different EN formulas at four
different stabilizer levels.
#3. Wire leads are applied.
#4. Leads are pull tested to failure.

19. Performance Testing Acceptability Criteria
Pass
Wire breaks, other than at neck
Pad (foil copper) pulls from substrate
Fail
Wire separates from pad
Neck of wire breaks

20. Assembly Performance Results- Pull Test

21. Solder Joint Shear Test Results

22. 9026M Additives The EN System Improved !
New Additives for improved circuit board performance (assembly).
Improved system eliminates break-down and co-deposition mechanism. No “black pad”.

23. 9026M Deposit Shelf Life Testing
Average Wetting 5 MTO’s
85% RH + 85°F aging

24. Summary
Typical Metal Finishing formulations are not well suited for Printed Circuits.
Although some Additives are in low concentrations (ppm), they have profound effects on the deposit composition and structure.
When “black pads” are seen, higher than normal conventional Additive concentrations are usually the culprit.
Even at much higher than normal concentrations, the 9026M Additives will not cause assembly rejects.