The capability extract shows in thirty seconds what runs as standard and what carries a surcharge.
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To the data check →Chip-on-board puts a bare die straight onto the PCB and connects it with wire thinner than a hair. Everything then depends on the bond pad: its finish, its roughness, its cleanliness, and how much room the bonder head has around it.
Two bonding processes dominate and they want different surfaces. Gold ball bonding uses heat and ultrasound to weld a gold wire to a gold pad — it needs ENEPIG, where a thin gold layer below 0.1 µm sits on palladium, or electrolytic gold of 0.3 to 0.5 µm. Aluminium wedge bonding welds aluminium wire cold, works on aluminium or gold, and is preferred for power devices because thicker wire carries more current.
ENEPIG — electroless nickel, electroless palladium, immersion gold — is the finish that does both. The palladium layer stops the nickel diffusing into the gold, so the surface stays bondable after storage and after a reflow cycle. That is why a board carrying both a bonded die and reflowed components almost always ends up on ENEPIG.
ENEPIG supports gold ball bonding, aluminium wedge bonding and normal reflow soldering. A hybrid assembly needs only one finish.
Removing the package removes its thermal resistance, its parasitic inductance and its footprint. For power and RF that is often the whole point.
Bond pads down to 100 µm pitch, far below anything solderable — the wire is thinner than a solder ball by an order of magnitude.
| Parameter | Standard | Advanced | Note |
|---|---|---|---|
| Finish | ENEPIG | hard gold | Both bondable; ENEPIG also solderable |
| Gold thickness | < 0.1 µm | 0.3 – 0.5 µm | ENEPIG bonds on thin gold over palladium; electrolytic gold needs the thicker layer |
| Palladium layer | 0.05 – 0.15 µm | 0.2 µm | Diffusion barrier — the key ENEPIG layer |
| Nickel layer | 3 – 6 µm | 5 – 7 µm | Under the palladium |
| Bond pad pitch | ≥ 125 µm | ≥ 100 µm | Centre to centre |
| Bond pad size | ≥ 100 µm | ≥ 80 µm | Square or rectangular |
| Surface roughness | Ra ≤ 0.4 µm | Ra ≤ 0.3 µm | Rough pads give inconsistent bonds |
| Mask clearance | ≥ 200 µm | ≥ 150 µm | Resist must be well clear of the pad |
Guide values for pre-selection. Binding values are confirmed per project against your data.
The points below are what most often comes back as a query after data review. Settling them before layout freeze saves a loop.
The bonder head needs physical room and the pad needs to be entirely free of resist. Allow at least 150 – 200 µm clearance, considerably more than a normal solder pad.
Bond quality depends on a smooth, consistent pad. Roughness above about Ra 0.4 µm gives scattered pull-test results even when the finish thickness is correct.
Bondability degrades with contamination and handling far faster than solderability. Vacuum pack, and plan the bonding step close to delivery.
A bond wire arcs above the board. Components placed too close to the bond pad row interfere with the loop and with the bonder head — the constraint is mechanical, not electrical.
ENEPIG for almost everything — it bonds and solders, and it is cheaper than plating hard gold over a large area. Hard gold is for cases where the pad must also take mechanical wear.
Gold for fine pitch and small signal currents; aluminium for power, because the wire can be much thicker. Aluminium wedge bonding also runs cold, which suits temperature-sensitive assemblies.
Not reliably. The nickel diffuses into the thin immersion gold over time and the bond fails. ENEPIG exists precisely to solve that with the palladium barrier.
Sealed and handled correctly, several months. But bondability is much more sensitive than solderability, so plan the process to bond as soon as practical after delivery.
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