Short answer
Clean the pad, degrease it with an absorbent pen at 10 to 12V DC, then plate tin at 6 to 8V with the part on the negative lead and the pen on the positive. Tin plates directly onto copper and most other metals (not aluminum or chromium), so no underlayer is needed.
Why pads stop taking solder
Tin surfaces oxidize with age and storage. Once the oxide builds up, solder beads up instead of wetting the pad. Re-plating a fresh tin layer on just the affected pads or leads brings back normal soldering behavior.
Step by step
- 01
Remove oxide and discoloration
If the surface is discolored or oxidized, polish it with a fine metal polish until the oxide is gone, then wipe it clean with a lint-free cloth.
- 02
Degrease at 10 to 12V
Set the supply to 10 to 12V and use the Absorbent / Degreaser pen (PL-1002). Connect the part to the negative (−) lead of the power supply and the pen to the positive (+) lead. Hold the pen so the whole tip touches the surface, and move it lightly back and forth in a slow stroke. Small bubbles form as oil and grease come off. Rinse with water when done. Stainless steel takes the Stainless Steel Degreaser pen (PL-1014) instead.
- 03
Plate tin at 6 to 8V
Set the supply to 6 to 8V and use the Tin pen (PL-1012). Connect the part to the negative (−) lead of the power supply and the pen to the positive (+) lead. Hold the pen so the whole tip touches the surface, and move it lightly back and forth in a slow stroke. Expect about 0.3 µm in 2 minutes and 0.5 µm in 3 minutes on a 1 in² area.
- 04
Rinse and wipe
Rinse with water and wipe with a soft cloth. The pad is ready to solder.
Substrate check
Tin plates over any metallic surface except aluminum and chromium. Copper pads, brass terminals and steel leads all take tin directly.
Parts list
- Micro-Metallizer Power Supply (PL-1000), $220
- Connector Cables (PL-1001), $20
- Absorbent / Degreaser pen (PL-1002), $65
- Tin plating pen (PL-1012), $70
Total $375. If you also restore gold contacts, the Contact Repair Kit ($400) includes the supply, cables, absorbent, nickel and gold pens; add the Tin pen for $70.
Frequently asked questions
How do you fix PCB pads that will not take solder?
Remove the oxide, degrease at 10 to 12V DC with an absorbent pen, then re-plate tin at 6 to 8V with a tin plating pen. This restores solderability on the pad without reworking the board.
Do I need a nickel or copper layer before tin?
No. Tin plates directly over copper and most other metals. The exceptions are aluminum and chromium.
How thick is brush-plated tin?
About 0.3 µm in 2 minutes and 0.5 µm in 3 minutes on a 1 in² area with a standard tin pen.
Not sure which pens your part needs?
Tell us the substrate and the finish you need. The people who build the system will tell you the sequence.