Post on 14-Apr-2016
description
Stress tabs Study06/11/2013
Dec-13 2
Content
1. Stress tabs study silver process with cumulative layers1. Stress sum up
1. Stress sum up characterization2. Individual stress per each bath
1. Stress sum up
2. Stress tabs study copper process with cumulative layers1. Stress sum up
1. Stress sum up characterization2. Individual stress per each bath
1. Stress sum up
3. Comparison of individual stress of each layer4. Final stress: Silver vs Copper5. Stress referential6. POP plating solution using additives7. Stress measurement
ContextHigh rate of blisters present in our actual plating process. Defectdetected mainly on silver QLF.• hypothesis is that after plating the layers had a stress that could
impact in a direct way the blistering on them.• Stress study is developed to analyse the behavior of the deposit.
Compresive stress Tensile stress
1.- Stress tabs study silver process with cumulative layers
• Individual and accumulated coatings were check with the stress tabs to see how is the behavior of each deposit in our actual silver process.
Nickel electroless bath
Compressive stress
Silver bath
Compressive stress
Nickel electroless + Ag
Compressive stress
Compressive stress
Compressive stress
Line 1 + Oven
Line 1 + Oven + Ni electro previous Line 1 + Oven + Line 2
Compressive stress
Line 1 + Oven + Line 2 + oven
Compressive stress
1.- Stress tabs study SILVER process with cumulative layers
SummaryCummulative
ProcessCommulative
Stress followingElectroless nickel (EN) Compressive
Ag Compressive
EN+Ag Compressive
EN+Ag+8hr HT200°C Compressive
EN+Ag+8hr HT200°C+Flash NiElectro Compressive
EN+Ag+8hr HT200°C+Flash NiElectro+2nd EN +NiElectro Compressive
EN+Ag+8hr HT200°C+Flash NiElectro+2nd EN +NiElectro+1hrHT200°C Compressive
Observation:Comulative stress on stress tabs has shown the same type of stess on silver process.
Then is needed to evaluate the individual stress per each type of layer/process in order to have a better understanding of each coating.
1.1.- Stress sum up.
• In order to understand the impact of the stress on Blisterseach test was characterized to see its impact from:• heat treatment• Thermal shock• Scrib test
Type of characterization
Silver Process
NIX NIX+Ag NIX+AgPre+Ag NIX+AgPre+Ag+oven Line 1+NIPre Line 1+NIPre+NIX2 Line1+Line2 Line1+Line2+oven
Compresive X X X X X X X X
Tensile
Scrib test result OK OK OK OK OK OK OK OK
Thermal shock OK OK OK OK OK OK OK OK
Characterization results
1.1.1.- Stress sum up characterization.
Dec-13 8
Nickel electroless bath
Compressive stress
Silver bath
Compressive stress
Electrolytic nickel FLASH
Compressive stress
2nd Nickel electroless bath on line 2
Compressive stress
Electrolytic nickel
Compressive stress
1.2.- Individual stress per each bath
SummaryCummulative
ProcessCommulative
Stress followingElectroless nickel (EN) Low-Compressive
Ag Very low - Compressive
Nickel electrolytic FLASH Compressive
Electroless nickel Compressive
Nickel electrolytic Very high - Compressive
According to individual stress observation has been detected that the electrolytic nickel has a very high compressive stress compared with the others
Hypothesis:This high compressive stress and good adherence could lead the coating to remove the underlayers between electroless nickel and silver due to very low compression of silver that seems to be very ductil.
1.2.1.- Stress sum up.
2.- Stress tabs study COPPER process with cumulative layers
• Individual and accumulated coatings were check with the stress tabs to see how is the behavior of each deposit in our actual copper process.
Nickel electroless
Compressive stress
Line 1 + Oven + Ni electro previous+ 2nd Electroless nickel
Null tensile stressCompressive stress
Copper
High Tensile stress
Nickel electroless + Copper
Mid Tensile stress Low tensile stress
Line 1 + Oven (copper)
Low tensile stress
Line 1 + Oven + Ni electro previousLine 1 + Oven + Ni electro previous+ 2nd Electroless nickel+ Ni Eletro
Low compressive stress
Line 1 + Oven + Ni electro previous+ 2nd Electroless nickel+ Ni Eletro+Oven
Mid compressive stress
2.- Stress tabs study copper process with cumulative layers
SummaryCummulative
ProcessCommulative
Stress followingElectroless nickel (EN) Compressive
Cu High tensile
EN+Cu Mid tensile
EN+Cu+1hr HT200°C Low tensile
EN+Ag+8hr HT200°C+Flash NiElectro Mid tensile
EN+Ag+8hr HT200°C+Flash NiElectro+2nd EN Null tensile
EN+Ag+8hr HT200°C+Flash NiElectro+2nd EN +NiElectro Null Compresive
EN+Ag+8hr HT200°C+Flash NiElectro+2nd EN +NiElectro+1hrHT200°C Mid Compressive
Commulative stress on stress tabs has shown the same type of stess on silver process.
Then is needed to evaluate the individual stress per each type of layer/process.
2.1.- Stress sum up
2.1.1.- Stress sump up characterization
Type of characterization
Copper ProcessNIX NIX+Cu NIX+Cu+Oven Line 1+NIPre Line 1+NIPre+NIX2 Line1+Line2 Line1+Line2+oven
Compresive X X X
Tensile X X X X
Scrib test result OK OK OK OK OK OK OKThermal shock OK OK OK OK OK OK OK
• In order to understand the impact of the stress on Blisterseach test was characterized to see its impact from:• heat treatment• Thermal shock• Scrib test
Characterization results
First nickel layers is compresive, but immediatly after copper bath the deposit becomes tensile, and it stays in this way until electrolytic nickelwhere changes to compresive. This means that the sum of the stress of all the line 1 until electroless nickel of line 2 is not giving compresivestress, just after electrolytic nickel it has this effect.
Scrib test and thermal shock are Ok for all the accumalated coatings.
Dec-13 14
Nickel electroless bath
Compressive stress
Electrolytic nickel FLASH
Compressive stress
2nd Nickel electroless bath on line 2
Compressive stress
Electrolytic nickel
Compressive stress
2.2.- Individual stress per each bathCopper
High Tensile stress
2.2.1.- Stress sum up
SummaryCummulative
ProcessCommulative
Stress followingElectroless nickel (EN) Low-Compressive
Cu Very high tensile
Nickel electrolytic FLASH Compressive
Electroless nickel Compressive
Nickel electrolytic Very high - Compressive
According to individual stress observation has been detected that the electrolytic copper has a very high tensile stress compared with the others, in other side electrolytic copper has the opposite phenomena with very high compresive stress.
Hypothesis:The different combination of stress of copper process could explain that plated parts with copper underlayer are less sensitive to stress and thus to blisters due to the opposite forces that copper process present vs the electrolytic nickel (Tensile vs compressive)
Type of characterization
INDIVIDUAL TESTNIX Ag Cu NIPre NIX2 NIE
Compresive X X X X X
Tensile XScrib test result OK OK OK OK OK OK
Thermal shock OK OK OK OK OK OK
3. - Comparison of individual stress of each layer
• All individual stresses are compresive, only copper is tensile, this is why thehypothesis of blisters appear in silver process.
• Scrib test and thermal shock are Ok for all the accumalated coatings.
4.- Final stress: Silver vs Copper
Line 1 + Oven + Line 2 + oven
Compressive stress
Line 1 + Oven + Ni electro previous+ 2nd Electrolessnickel+ Ni Eletro+Oven
Mid compressive stress
Regarding the different stress behavior between Silver and Copper has been observed that Silver process has an important compressive stress at the end of the plating process which include EN, Silver, NiElectroFLASH+EN+Nielectro compared with the copper process.
This phenomena can be an input to issue of lack of adhesion.
5.- Stress referential
Different type of stress on metals.
Stress on plating process can be modified by the addition of organic agents on plating solutions known as carriers and brightneers, these agents have an important contribution to stress either compressive or tensile on each plating solution.
6.- POP solutions using additives.
• Copper:• CarrierD / Carrier / additive (Brightener)
• Silver:• Brightener
• Electrolytic nickel• Carrier, Brightener and wetting agent.
There is no too much information available about stress influence from the different additives there are being usedinto the plating solutions like:
Efect of min/max carrier on Tensile / Compressive stress ¿?Efect of min/max brightener on Tensile / Compressive stress ¿?Efect of min/max wetting agent on Tensile / Compressive stress ¿?
“In order to answer above questions is needed to have quantitative stress measurement”
7.- Stress measurement
This instrument is to measure in a quantitave way the stress for the different plating solutions.
The instrument is already in Obregon and in progress to start working with it, so far is not a priority