The solder in a wave solder machine can become contaminated with other metals dissolved during the soldering process. These impurities can affect the physical characteristics and wetting ability of the solder, and may possibly result in defects such as icycling, bridging, pin-holes, webbing and non-wetting.
Below is a list of common wave solder contaminants, their allowable limits and the steps to take to correct these:
| Contaminant* |
Limit Precondition Surface % |
LimitWave or Pot Soldering % |
Possible Cause |
Corrective Action** |
| Cu |
.75 |
.30 |
Boards or leads have exposed copper |
Cool solder pot to 370°F for 8 hrs and remove dross |
| Au |
.50 |
.20 |
Gold pads or leads exposed to copper |
Same as for copper |
| Cd |
.01 |
.005 |
Cadmium coated shields or fixtures |
Dump pot |
| Zn |
.008 |
.005 |
Plated bolts or heat sink |
Dump pot |
| Al |
.008 |
.008 |
Heat sink fixtures |
Dump pot |
| Sb |
.50 |
.50 |
Not normally found except as an additive to solder |
Dump pot |
| Fe |
.02 |
.02 |
Occurs if pot is over heated; from pot, pump or other surfaces in the wave. |
Dump pot |
| As |
.03 |
.03 |
Not normally found except as a contaminant from recycled solder |
Dump pot |
| Bi |
.25 |
.25 |
Contact w/some surface finishes |
Dump pot |
| Ag |
.75 |
.10 |
Contact w/some lead finishes |
Dump pot |
| Ni |
.025 |
.01 |
Contact w/stainless steel |
Dump pot |
| * |
Limits set from IPC J-STD 001C DOD 2000A |
| ** |
When precipitating copper from a pot make sure the pot is stagnant and is undisturbed for at least 8 hours. |
| Tin levels will typically drop over time. ±1.5% of the nominal tin content is acceptable. To raise this level, calculate the weight in your pot times the analyzed percentage. This gives the actual weight of tin. Take the weight of solder held by the pot and multiply it by .63; this is the amount of tin that should be in the pot. Subtract the analyzed weight from the theoretical weight. This is the amount of tin needed in the pot. Remove 15% more solder than this and add the calculated amount of tin. Top off the pot with bar solder. |
Solder Analysis Service
The AIM Solder Analysis Service is a program of scheduled analyses that can increase wave soldering throughput and reliability and reduce the rework of soldered assemblies. In order to maintain solder purity, a program of regularly scheduled pot analysis is recommended. The program allows customers to track solder pot impurities for conformance to IPC and/or internal requirements.
Analysis Report
AIM's Solder Pot Analysis Program provides a complete quantitative report on solder pot composition for preventive maintenance or for solving specific solder-related problems. AIM's analytical services are most often used to assure the solder pot has not become contaminated with other metals. Samples are analyzed to determine concentrations for tin and lead and a wide variety of contaminants through the use of analytical spectroscopy. Below is a copy of a typical solder analysis report:
| Element |
Result % |
Limits (1) |
| Sn |
Tin |
63.1 |
(2) |
| Pb |
Lead |
Balance |
(2) |
| Sb |
Antimony |
0.021 |
0.500 |
| Cu |
Copper |
0.136 |
0.300 (4) |
| As |
Arsenic |
0.012 |
0.030 |
| Ag |
Silver |
0.003 |
0.100 (3) |
| Bi |
Bismouth |
0.006 |
0.250 |
| Cd |
Cadmium |
< 0.001 |
0.005 (4) |
| Al |
Aluminum |
< 0.001 |
0.006 (4) |
| Fe |
Iron |
< 0.002 |
0.020 |
| Ni |
Nickel |
0.002 |
0.010 |
| Zn |
Zinc |
<0.001 |
0.005 (4) |
| Au |
Gold |
0.037 |
0.200 (4) |
| 1 |
Recommended maximums (%) for sn60-sn63 (assembly soldering: pot, wave, etc.) / according to IPC J-STD-001B |
| 2 |
+/- 1.5 % of nominal |
| 3 |
Or Sn62: 1.75% - 2.25 % |
| 4 |
Assembly soldering: total of Cu, Au, Cd, Zn, Al should not exceed 0.4% |
How to Order the Service
- Customer provides a purchase order for a certain number of solder analysis envelopes and is billed accordingly.
- The envelopes are sent to the customer via USPS unless the customer has an urgent need for them. In this case, the envelopes will be sent via FedEx or UPS at the customer's expense.
- Customer sends in a sample for analysis, using an authorized envelope. The sample should be 1" wide x 2" long or weigh 200 grams. Samples can be sent to the closest AIM facility or directly to AIM Montreal in urgent cases.
For additional details, please contact AIM at the numbers below or contact your local representative.