Back-drill aluminum is bought against a number rather than a feeling: the residual stub you have to live with. Two grades are published — HW600 at 0.16 mm and HW900 at 0.19 mm — and the choice between them sets the material, the tolerance you can hold and the price you pay. This page stands on the buyer’s side of that decision: how the grade is chosen, what the published sheet sizes and MOQ mean, how the quotation is built, what evidence a qualification file should contain, and how a trial order becomes a standing schedule. The process itself is covered in the back-drilling definition, and the technical selection logic in the material selection guide.
Both grades are one-piece coated aluminum entry material in the same 0.16–0.19 mm range, and they differ in what they are published to deliver:
| Grade | Total thickness | Published stub CpK target | Positioning |
|---|---|---|---|
| HW600 | 0.16 mm | ≥ 1.33 | Standard back-drill, cost-first evaluation |
| HW900 | 0.19 mm | ≥ 1.67 | Tighter-tolerance, high-speed evaluation |
The build underneath is common to both: AA1100 aluminium at 0.16 or 0.19 mm with a ±0.005 mm thickness tolerance, a 25–30 µm polymer coating for the entry and isolation layer, and a warpage limit of 0.6% of the diagonal. What differs is the thickness the process can hold against a target residual stub and a tighter tolerance tolerance band, and that is exactly what a buyer should be selecting on.
One caveat belongs in the same paragraph as the numbers. Construction alone does not guarantee a residual-stub result: the final stub control is a system outcome of stack-up, tooling, machine depth routine, panel flatness, fixturing and inspection method. The grade sets the entry condition; the process sets the result. The process reference and the measurement window are in the back-drill design rules.
Published sheet sizes are 940 × 1245 mm, 1040 × 1245 mm and 1090 × 1245 mm, with other sizes on request. Published MOQ follows the format, the same way it does for backup board:
| Sheet size | Grade | Published MOQ |
|---|---|---|
| 940 × 1245 mm | HW600 / HW900 | 100 sheets |
| 520 × 620 mm | HW600 / HW900 | 200 sheets |
What pushes a minimum up here is the same as anywhere else in the range: a format that is not in running stock has to be scheduled, and a coated grade has to be planned into the press calendar rather than pulled from stock. The practical consequence for a buyer is that the standard formats are the cheap way to start, and a special size is a schedule conversation, not a quantity conversation.
Aluminum entry material is priced on a pass-through formula — the SMM aluminum spot price plus a conversion charge — rather than on a fixed rate. A quotation therefore carries a metal reference date and a validity window, and both belong in the file. Three things a buyer should confirm on the quote itself:
The cost per hole, rather than the cost per sheet, is what decides whether a grade is worth its price, and the way to convert is set out in the procurement walkthrough. The conversion can be run on your own figures in the drilling cost calculator.
Back-drill material is the one consumable where the buyer’s own process and the material have to be qualified together, so the file is the deliverable of the trial rather than a formality at the end of it. Six items belong in it:
Those conditions are why a published test result from a supplier cannot be taken as a guarantee for your line, and the reporting standard we hold ourselves to is written out on the back-drill aluminum product page. The document set on the supplier side — TDS, COA, SDS, declaration — and the sequence in which a supplier is qualified are in the supplier qualification guide.
A trial order is not a small order with a different label, and the two should not be quoted the same way. A trial establishes the process window; a first order establishes the supply line. Three things differ:
For a material this specification-sensitive, the incoming check on the first delivery is worth widening beyond the routine one — lot COA against the current TDS revision, a dimensional spot-check across the sheet, surface and packaging condition, and a retained sample filed against the lot number. The full sequence from sample approval to standing volume supply is in the first-order ramp guide, and the production-side verification and ramp routine is in the back-drill production ramp guide.
Once the grade and the process window are settled, the remaining risk is commercial rather than technical: metal movement, a silent specification change and a single-source dependency. Three arrangements address them, and they are worth having in that order:
The commercial structure that carries these arrangements, and the landed cost sheet they have to sit on, are in the the procurement and landed cost walkthrough; the supplier-side side of a second-source qualification is in the the supplier qualification walkthrough.
HW600 is the 0.16 mm grade with a published stub CpK target of at least 1.33, positioned for standard back-drill and cost-first evaluation. HW900 is the 0.19 mm grade with a published target of at least 1.67, positioned for tighter-tolerance and high-speed evaluation. Both use AA1100 aluminium with a 25 to 30 micron polymer coating and an aluminium thickness tolerance of plus or minus 0.005 mm.
No. The sheet sets the entry condition for the controlled-depth second pass, but the achieved residual stub is a system outcome of stack-up, tooling, machine depth routine, panel flatness, fixturing and inspection method. The achievable process window has to be confirmed on the buyer's own PCB stack and drilling equipment.
Published MOQ is 100 sheets at 940 by 1245 mm and 200 sheets at 520 by 620 mm, for both HW600 and HW900. A format that is not in running stock has to be scheduled rather than pulled from stock, so a special size is a schedule question rather than a quantity question.
On a pass-through formula of the SMM aluminum spot price plus a conversion charge, not on a fixed rate. A quotation therefore carries a metal reference date and a validity window. The quote should also state the Incoterm and named port, and the grade and gauge, since 0.16 mm and 0.19 mm are different products at different conversion charges.
The grade and gauge trialed against the TDS revision in force, the finished PCB thickness and stack-up, the back-drill side and target residual stub, the drill diameter and depth routine, the measurement method with the resulting CpK and its stated test conditions, and the lot COA with the traceability statement so the qualified lot can be found again.
The standard schedule is 30% deposit with the order acknowledgement and the balance settled before shipment. The standard one-week lead time starts from the acknowledgement and the deposit rather than from the enquiry, so the payment instruction is on the critical path. Any other payment arrangement has to be agreed before the acknowledgement is issued.