LE Sheet is the established industry term for a PCB mechanical-drilling entry sheet built from an aluminum sheet plus a lubricating layer. Mitsubishi Gas Chemical describes the lubricant as reducing drill wear, improving through-hole quality and hole-position accuracy, enabling higher stack height and extending drill-bit life. This page explains that material system; YUESHAN's commercial lubricant aluminum grades are handled separately. Two adjacent profiles complete the picture: the lubricated backup board on the exit side, and the phenolic entry board, which trades the lubricating film for positional rigidity.
Material Profile — Not a Product Listing
This page explains the LE Sheet / lubricant-coated aluminum material system: construction, coating chemistry, water solubility, heat/friction behavior and drilling-quality factors. For YUESHAN commercial grades, samples, TDS/SDS and quotations, use the Lubricant Aluminum product page.
What Is an LE Sheet?
Mitsubishi Gas Chemical (MGC), a primary industry source for the term, defines LE SHEET as an entry sheet for mechanical drilling consisting of a lubricating layer and an aluminum sheet. The material is used above printed wiring boards during drilling.
Across search results, the same material family appears under several related phrases: LE Sheet, lubricated entry sheet, lubricant aluminum entry sheet, lubricating aluminum entry board, coated aluminum entry sheet, lube sheet and PCB drilling entry sheet. These are useful wording variants, but coating chemistry and construction must still be checked before treating two grades as equivalent.
Because the term is used loosely across suppliers, the lubricated aluminium entry board article gives a plain-language overview of the same two-layer system before the coating details below.
LE Sheet Construction: Lubricating Layer + Aluminum Base
The basic material architecture is simple:
- Aluminum base: provides a flat, dimensionally stable entry layer and conducts heat away from the initial drill contact.
- Lubricating layer: reduces friction between the drill, chips and entry interface. Depending on chemistry, it may be water-soluble / hot-melt or a heat-stable coated film.
MGC publishes aluminum-sheet thicknesses in roughly the 70–150 μm class for its LE Sheet system. Chinese industry pages commonly publish total thickness, aluminum-base thickness and lubricant-layer thickness separately — for example 0.13 mm total with a 0.10 mm aluminum base plus 0.03 mm lubricant layer. These are useful benchmark categories, not YUESHAN specifications unless confirmed by the current TDS.
How the Lubricating Layer Works During Drilling
For water-soluble hot-melt systems, drilling heat softens or melts the lubricant at the contact zone. The lubricant can coat the drill and reduce friction while helping chips move up the flute. MGC states that this lowers frictional heat generation, reduces wear and helps debris discharge smoothly.
The material mechanism connects directly to the factors engineers search for:
- drill-bit wear / drill life;
- hole-position accuracy;
- hole-wall roughness;
- resin smear;
- wicking / plating soak-in;
- micro-cracks between glass fiber and resin;
- chip evacuation;
- stack height / number of overlaid boards;
- drilling cost per good hole.
One practical note on working points: a coated entry grade is only fully specified when it carries its qualified working window — the qualified hit counts per tool, the spindle-speed range and the minimum drill diameter the coating supports. Buyers comparing spec sheets will see these as per-model rows next to the thickness data; treat any such row as grade- and machine-specific rather than universal — the qualified window depends on the coating chemistry, the machine platform and the stack build. Ask for the working-window row on the current TDS for the exact grade you qualify, and re-confirm it whenever the coating chemistry changes.
Water-Soluble vs Thermoset Coating Systems
| Coating system | Material behavior | Engineering questions |
|---|---|---|
| Water-soluble / hot-melt lubricant | Softens or melts under drilling heat and can be removed with water rinse | Solubility, rinse conditions, humidity sensitivity, coating thickness, residue |
| Thermoset / heat-stable coating | Designed to remain dimensionally stable at higher temperature while providing a low-friction interface | Thermal stability, film uniformity, adhesion, drilling residue, compatibility with downstream cleaning |
Do not assume “LE Sheet” automatically means one chemistry. MGC's well-known LE Sheet is water-soluble; other suppliers market thermoset or alternative coated entry systems. Qualification should therefore specify both base aluminum and coating chemistry.
Two qualification lines sit around the coating itself. For water-soluble grades, verify the wash-off path: residue must clear in the aqueous cleaning or de-smear step before PTH, so rinse conditions belong in the qualification sheet alongside coating thickness. On compliance, coated grades are supplied with SDS and material declarations on request — RoHS restricts lead (Pb), cadmium (Cd), mercury (Hg), hexavalent chromium (Cr6+), PBB and PBDE, and the declaration you file should match the coating chemistry you qualify.
Choosing between an uncoated and a coated top sheet is mostly a question of hole size and heat sensitivity, and standard vs lubricated aluminium entry board works through that trade-off.
Hole Quality Factors: Smear, Wicking and Wall Roughness
MGC's published technical pages are especially useful because they describe the output variables rather than only the material. Their reported benefits include less hole-wall roughness, less wicking, less resin smear, improved hole-position accuracy, increased stack height and longer drill-bit life.
These terms should also guide internal process qualification. Instead of asking only “Did the coated sheet reduce temperature?”, track:
- position error / CpK;
- wall roughness after drilling;
- smear incidence after sectioning;
- wicking or resin/glass interface damage;
- drill wear after a defined hit count;
- breakage frequency;
- maximum qualified stack height;
- cleanability before subsequent plating.
If exit burr rather than smear is the limiting defect, the anti-burr aluminium entry board note reviews how coating choice and entry support interact at the drill exit.
Engineering Variables to Specify
| Variable | Why it matters | Common search / procurement wording |
|---|---|---|
| Aluminum alloy / base | Controls base-sheet mechanical and thermal behavior | 1100 aluminum, 1060 aluminum, aluminum foil base |
| Base thickness | Affects entry rigidity and total material thickness | 70–150 μm, 0.10 mm, 0.12 mm, 0.15 mm |
| Lubricant-layer thickness | Influences friction, heat transfer and coating consumption | lubricating layer, coating thickness, resin layer |
| Total thickness | Must fit drill diameter and stack geometry | 0.13 mm, 0.16 mm, 0.18 mm, 0.20 mm |
| Coating chemistry | Determines melting / thermal behavior and cleaning route | water-soluble, hot-melt, thermoset, polymer coating |
| Flatness / thickness tolerance | Supports repeatable Z geometry and drill entry | flatness, dimensional accuracy, thickness tolerance |
| Water solubility / cleanability | Relevant before PTH or downstream wet processing | water rinse, residue, washable coating |
| Hole-quality output | Validates the material under real drilling conditions | roughness, smear, wicking, CpK, drill life, stack height |
When to Evaluate Lubricant-Coated Entry Material
A lubricant-coated entry sheet becomes especially relevant as drill diameter decreases, hole density rises, stack height increases or the laminate becomes more sensitive to heat and smear. MGC's product lineup explicitly differentiates grades by PCB thickness and drill diameter, including very small-diameter drilling.
For YUESHAN commercial selection, use the Lubricant Aluminum product page. For application diagnosis, see the signs you need a lubricated entry sheet and lubricant coating thickness calculator.
Burr control is where the anti-burr behaviour of a lubricated entry sheet shows up as a measurable difference. Because the lubricating layer lets the drill leave the entry sheet with less chatter, the burr height left on the copper top surface drops along with the hole-wall scores — shops that log burr height next to roughness usually see the pair move together after switching from plain foil. Anti-burr is therefore not a separate coating function but a consequence of the same low-friction entry face described above.
External Technical References
- Mitsubishi Gas Chemical — LE SHEET overview
- MGC — LE SHEET effects: roughness, smear, wicking, position accuracy and drill life
- MGC — LE SHEET lineup by hole diameter
- IPC design standards
LE Sheet Material FAQ
What is an LE Sheet?
An LE Sheet is an aluminum entry sheet with a lubricating layer used for PCB mechanical drilling. The lubricant reduces friction at entry and can improve hole quality and drill life.
Is every LE Sheet water-soluble?
No. MGC's classic LE Sheet uses a water-soluble lubricant system, while the wider market also includes thermoset and other coated entry technologies. Always specify the coating chemistry.
What drilling outputs should be measured during qualification?
Hole-position accuracy, wall roughness, smear, wicking, drill wear, breakage, stack height and cleanability are more meaningful than coating name alone.
Is this YUESHAN's lubricant aluminum product page?
No. This is a technical material profile. For commercial grades, sizes, samples and TDS/SDS, go to YUESHAN Lubricant Aluminum.