Lead Free Solder Comparisons
Proposed range Typical Comp.
Sn-3.5Ag
Sn-Ag-Cu
Sn-Ag-Cu-Sb
Sn-0.7Cu
Sn-Bi-Ag
Sn-Zn-Bi
Melting/process temperature
5
3.5
3.5
6
2
1
Fillet lifting resistance(1)
2.5
2.5
2.5
2.5
5.5
5.5
Solderability(2)
4
2
3
5
1
*10
Processability(3)
3
1.5
1.5
5
4
*10
Reliability(4)
3
1.5
1.5
4
5
6
Recyclability(5)
2.5
2.5
2.5
2.5
5
6
Cost(6)
4.5
4.5
4.5
1.5
4.5
1.5
Alloy availability(7)
1.5
3
4
1.5
5
6
TOTAL SCORE
26
21
23
28
32
46
AVERAGE SCORE
3.3
2.6
2.9
3.5
4.0
5.6
3.4 – 4.1 % Ag 2.5 Ag
plus 0.8Cu
0.45 - 0.9 % Cu 0.5Sb1 GOOD- 6 POOR- 10 BAD
NOTES:
Bi alloys most prone to fillet lift, and most problems with Pb contamination
Zn alloy oxidation, requires very strong flux
SnAgCu(Sb) and SnBiAg advantage of lower temperature, but with SnBiAg must consider fillet lifting
On average only; different/best service conditions can give different ranking
Zn and Bi increase problems/cost; some pros and cons for all other alloys
Approximate relative cost: dependent on Ag content: more effect on bar than paste
SnAgCu some patents; SnAgCuSb patented and licensed; SnBiAg and SnZnBi various patents
Alchemy ‘C’ Tin-Copper Trial Report
Date: 20th & 21st January 1999
Location: Quicksilver Services in Galashiels (Cemco HASL Service Centre)
Purpose: To determine Alchemy capability when using a 'Lead-Free' solder alloy of Sn 99.3% + Cu 0.7%. To experiment with the process parameter settings to produce the best possible product quality when running a) Air, b) Nitrogen, through the air the knives to compare results.
Solder temperature 280C (536F)
Air Heat Exchanger 300C (572F)
Air Knives 275C (527F)
The increased solder temperature (with SnPb the temperature would typically be 250C/482F) had the effect of raising the oil temp from a normal running of 230C (446F) to 255C (491F)
RUN PARAMETER DATA
Board Number
Board temp
Pre-Heat
(MPM)
Level Speed (MPM)
Bar Pressure
Top/Bot
Gap (mm)
Off Set (mm)
Board Type
1.6mm (0.062")
Gas Used
1
196
2.3
24
1/1.1
3.05
1.75
Non Drilled D/S
Air
2
228
1
24
1.1/1.2
3.05
1.75
D/S
Air
3
217
1
20
1.35/1.45
3.05
1.75
D/S
Air
3
212
1
20
1.35/1.45
3.05
1.75
6 layer Multilayer
Air
4
224
1
20
1.35/1.45
3.05
1.75
6 layer Multilayer
Air
5
227
1
20
1.2/1.3
3.05
1.75
6 layer Multilayer
Air
6
220
1.3
25
1.15/1.25
3.05
1.75
D/S
Air
7
220
1.3
24
1.15/1.3
3.2
1.75
D/S
Air
7b (3 off)
220
1.3
24
1.15/1.3
3.2
1.75
Drilled/Non Drilled D/S
Air
8
209
1.3
24
1.0/1.15
3.2
1.75
Rework Multilayer
Nitrogen
9
218
1.3
24
1.0/1.15
3.2
1.75
Rework Multilayer
Nitrogen
10
218
1.3
24
0.95/1.1
3.2
1.75
Rework D/S
Nitrogen
11
218
1.3
24
0.9/1.0
3.2
1.75
Rework D/S
Nitrogen
12
203
1.3
22
1.1/1.2
3.2
1.75
Rework Multilayer
Nitrogen
Note: Pre–heat speed based on using two Pre-heat modules. (MPM) meters per minute.
