For plain multilayer boards with holes above 0.20 mm, standard 1100 H18 full-hard aluminum entry (0.15-0.20 mm) is sufficient and cheapest. For HDI, BGA, IC or holes below 0.20 mm, a lubricated sheet adds a 3-5 um thermoset coating at ~220 C that cools the bit, extends life and cuts smearing.
If you are evaluating whether to switch from plain aluminum entry to lubricated (LE/coated) entry board, here is the short answer upfront: for standard multilayer boards with hole sizes >0.20 mm, plain aluminum is sufficient. For HDI, microvia (<0.15 mm), IC substrate or high-layer-count boards, lubricated aluminum pays for itself through longer bit life, fewer burr defects, and lower total cost per good panel. This article explains why — and how to calculate the break-even point for your specific production line.
What is the difference?
Standard aluminum entry board is a plain sheet of 1100 H18 full-hard aluminum, typically 0.15–0.20 mm thick. Its job is to guide the drill bit on entry, reduce burr formation, and dissipate heat. It is the workhorse entry material for the majority of PCB drilling worldwide.
Lubricated aluminum entry board (also called LE sheet or coated aluminum) starts with the same 1100 H18 base but adds a thin thermoset resin coating — typically 3–5 µm — on one or both sides. At approximately 220°C (the peak temperature the entry board reaches during drilling), this coating melts and acts as a boundary lubricant between the drill bit and the aluminum. The result: lower friction, lower peak bit temperature, less aluminum adhesion to the flute, and cleaner hole walls.
Quick comparison table
| Attribute | Standard Aluminum Entry | Lubricated (LE) Aluminum |
|---|---|---|
| Construction | 1100 H18 plain aluminum | 1100 H18 + thermoset coating (3-5 µm) |
| Thickness range | 0.15–0.20 mm | 0.08–0.15 mm |
| Coating melt point | N/A | ~220°C |
| Lubrication mechanism | None (bare aluminum) | Molten film boundary lubrication |
| Unit price per sheet | $ (baseline) | $$$ (2–3× baseline) |
| Best hole size range | ≥0.20 mm | ≤0.20 mm (optimal at ≤0.15 mm) |
| Bit life vs plain Al | Baseline | +30–50% (field verified) |
| Exit burr control | Good (≥0.20 mm holes) | Excellent (≤0.05 mm achievable) |
| Resin smear prevention | Limited | Yes — lubrication reduces heat buildup |
| Max spindle speed | Up to 200 krpm | 250+ krpm |
| Ideal for | Standard multilayer, double-sided | HDI, BGA, IC substrate, high-layer |
When plain aluminum is the right choice
For many PCB fabricators, standard aluminum entry board is all they need. You do not need lubricated aluminum if:
- Your smallest hole size is ≥0.20 mm — Standard entry provides adequate burr control and bit life at this diameter. The additional cost of LE sheet does not justify the marginal improvement.
- Your layer count is ≤8 layers — Thinner stacks generate less friction heat. The thermal load on the entry board is lower, and plain aluminum dissipates heat well enough.
- Your spindle speed is ≤150 krpm — At lower RPM, the friction between bit and entry board is manageable without lubrication. Bit wear from entry-board friction is not your dominant cost driver.
- You are running FR4 or standard materials only — If the panel material itself does not generate aggressive heat or produce problematic resin smear, plain entry is sufficient.
When lubricated aluminum pays for itself
The unit price of LE sheet is 2–3× that of plain aluminum. The question is not which is cheaper per sheet — it is whether the premium pays for itself in production savings. Here is when it does:
1. Microvia and HDI drilling (<0.15 mm holes)
At hole diameters below 0.15 mm, the drill bit is extremely fragile. The friction from entering a plain aluminum sheet at 200+ krpm generates enough heat to soften the bit's carbide edge, accelerating wear. LE coating reduces entry friction by 30–50%, measured by spindle load current. The result: bits last 40–70% longer on Ø0.10 mm microvia programs when used with LE entry versus plain aluminum.
The saving: If a micro-drill costs $0.80 and you are resharpening every 1,000 hits with plain entry, switching to LE sheet can extend that to 1,500 hits. The 500 extra hits per bit — across 100,000 holes per shift — saves $53 per bit change cycle in tooling cost alone.
2. High-layer-count boards (16+ layers)
Thick stacks generate more heat because the drill bit spends more time in the stack. Heat accumulates in the entry board region, and without lubrication, this heat can cause resin smear on the inner layers of the bottom third of the stack. LE sheet's lubricating film reduces peak entry temperature by 15–25°C, directly reducing resin smear risk.
The saving: A single scrapped 16-layer panel from smear-related inner-layer damage costs $50–200 in material alone. If LE sheet prevents even one scrapped panel per shift, it covers the entire day's premium over plain aluminum.
3. IC substrate and BGA packaging
These applications demand Ø0.08–0.10 mm holes with tightest burr specs (<0.03 mm). Plain aluminum entry cannot consistently hold this tolerance. LE sheet's lubricating action reduces exit burr variation by 40–60% compared to plain aluminum, based on CpK data from production lines.
Cost-benefit analysis: a worked example
| Cost factor | Plain Aluminum Entry | Lubricated Aluminum Entry |
|---|---|---|
| Entry board cost per panel (est.) | $0.08 | $0.22 |
| Bit cost per 1,000 holes | $1.06 (1.33 bits @ $0.80) | $0.80 (1.0 bits @ $0.80) |
| Bit change downtime cost per 1,000 holes | $0.42 | $0.28 |
| Scrap rate from burr defects | 2.5% | 0.8% |
| Scrap cost per 1,000 panels | $50.00 | $16.00 |
| Total cost per 1,000 panels | $51.56 | $17.30 |
Note: These are representative estimates based on field data from HDI production lines. Your actual savings depend on your specific hole size, stack height, drilling machine, and bit type. Run a side-by-side trial to measure your own numbers.
The table makes one thing clear: the entry board unit price is a small fraction of the total cost per good panel. Bit life improvement and scrap reduction easily offset the sheet-price premium in the applications where LE sheet is specified correctly.
How to decide: a decision framework
| If your production looks like... | Your entry board should be... | Why |
|---|---|---|
| Double-sided boards, ≥0.25 mm holes, FR4 | Standard aluminum entry (0.15 mm or 0.20 mm) | Plain Al is cost-optimized for this profile |
| 4–8 layer multilayer, 0.20–0.30 mm holes | Standard aluminum entry | Adequate burr control, no premium needed |
| 8–16 layer, 0.15–0.20 mm holes | Standard or LE (trial recommended) | Test 100 panels to see if bit life improvement covers the premium |
| HDI, 6–20 layer, ≤0.15 mm microvia | Lubricated aluminum entry (lubricated vs plain entry board) | LE pays for itself in tooling + scrap reduction |
| IC substrate / BGA, ≤0.10 mm holes | Lubricated aluminum entry | Required for burr spec <0.03 mm |
| High-layer backplane, 20+ layers | Lubricated aluminum entry | Prevents resin smear in deep stacks |
FAQ
Can I use LE sheet on all my boards? You can, but it is not cost-effective for simple boards. Reserve LE for the applications where its properties save you money elsewhere.
Does LE sheet require different drilling parameters? Minor adjustments may be needed. The lower friction means you can sometimes increase feed rate by 5–10% without sacrificing quality. Your YUESHAN sample shipment includes recommended parameter starting points.
How do I run a comparison test? Split a production panel — plain Al on one half, LE on the other. Measure burr height, bit wear (hits before regrind), and scrap rate. Most customers see clear differences within 500–1,000 holes.
Is "lubricated aluminum" the same as "coated aluminum"? Yes — the terms are used interchangeably. Some suppliers call it LE (lubricated entry), coated aluminum, or thermoset aluminum entry. They all refer to the same technology: a plain aluminum base with a thin thermoset coating.