During CAM preparation of a 6-layer HDI order classified as 2+N+2, our team identified three items that required customer confirmation before tool generation. The board measures 68 mm by 116 mm, uses Kingboard KB-6165F FR-4 with TG150, is specified at 1.0 mm finished thickness with 1 oz copper on outer and inner layers, carries blue solder mask and white silkscreen, and requires resin plugging of vias. Blind and buried vias are indicated, the minimum hole size is listed as 0.15 mm, separation combines V-cut and routing, and the delivery format is customer self-panelization in a 1×2 array with no process edge. Mechanical forming is specified and no impedance control is required. These parameters establish a compact 2+N+2 structure HDI construction in which scoring locations, drill-to-outline consistency, and the sequential lamination used for the blind vias must be verified.
The main engineering questions centered on a location we judged to require V-cut, a set of holes whose diameters did not match the outline circles shown in the data, and an optimized lamination drawing in which the board is built according to the prior-board stackup while the blind vias are reduced to 0.1 mm. Each item was submitted with supporting figures for confirmation.
V-Cut Position Verification for a 1×2 HDI Panel
An arrow in the supplied data marked a position that our review interpreted as requiring V-cut. We asked the customer to confirm whether that judgment was correct. The order ( #HDI-20251022-0007 ) already lists separation as V-cut plus routing and shows a 1×2 customer self-panel with no process edge. In such a format the V-cut lines define the break-away paths between the two circuits; an incorrectly placed score can either leave the boards joined or cut into functional copper or holes.
Because the panelization is customer-supplied, the factory does not generate the array but must still program the V-cut and routing tools to match the intended separation. The arrowed location was therefore flagged so that the scoring path could be locked before the mechanical-forming programs are released. Confirmation ensures that the V-cut coincides with the customer's intended break line and does not intersect the 0.15 mm holes or the resin-plugged vias. On a 1.0 mm board the V-cut depth must also be controlled to leave a residual web that separates cleanly without damaging the 2+N+2 HDI structure.
Figure 1: The position as shown by the arrow will be V-cut.
HDI Drill Size Verification and Hole-to-Outline Mismatch
A second figure showed a group of holes whose diameters did not correspond to the circles drawn on the outline layer. We requested confirmation of the intended size. In HDI data it is not uncommon for the outline or drill drawing to contain nominal or reference circles that differ from the actual drill file; when the discrepancy is left unresolved, the finished hole may be larger or smaller than the capture pad or the annular ring expects.
Figure 2: This kind of hole size as shown by the arrow is not in accordance with the outline circle.
The order lists a 0.15 mm hole size and indicates blind/buried vias with resin plugging. For a 2+N+2 construction the smallest features are typically the laser-drilled blind vias, while mechanical drills handle the larger through holes. A mismatch between the plotted circle and the drill diameter can therefore affect either the laser program or the mechanical drill chart. Confirmation establishes which value governs so that the drill files, the resin-plug process, and the subsequent plating to the stated 18 µm hole-wall copper can be generated consistently. On a board only 1.0 mm thick, even a small diameter error changes the aspect ratio and the reliability of the plated barrel.
6-Layer HDI Stackup Optimization with 0.1 mm Blind Vias
We proposed to fabricate the board according to the lamination sequence used on the prior board and to reduce the blind vias to 0.1 mm. An optimized stackup drawing was attached for confirmation. The order form marks HDI order as 2 and blind/buried vias as present, yet lists no customer stackup requirement. In a 6-layer HDI board the blind vias are formed by laser drilling after the first lamination; their diameter must lie within the laser process window and must register to the capture pads on the adjacent layers.
Reducing the blind vias from the 0.15 mm order-form value to 0.1 mm brings them inside a commonly supported laser range while preserving connectivity. The optimized drawing follows the dielectric and copper arrangement of the previous successful build, thereby reusing proven prepreg and core thicknesses for the Kingboard KB-6165F material at 1.0 mm finished thickness. Because resin plugging is specified, the smaller blind vias must still accept the plug material without voids. Confirmation of the drawing locks both the sequential lamination order and the laser-drill diameter before the sub-composite drills are programmed. The same confirmation also ensures that the 1 oz copper weights and the blue solder mask remain compatible with the revised via geometry.
Figure 3: The blind vias will be shrinked to 0.1mm for fabricating.
Figure 4: The attached picture is our optimizing stack up structure.
Key CAM Confirmations for 6-Layer HDI Manufacturing
The three items address distinct but concurrent aspects of releasing this 6-layer 2+N+2 HDI board. The V-cut judgment fixes the mechanical separation path on the customer-supplied 1×2 panel. The hole-to-outline mismatch clarifies which diameter governs the drill files that will later be resin-plugged and plated. The optimized lamination and 0.1 mm blind-via size establish the sequential build and laser program that create the HDI interconnects. All three must be resolved before the drill, score, and lamination tools can be finalized.
None of the points can be closed by the factory alone. The original data either left the V-cut location ambiguous, showed inconsistent hole graphics, or omitted a stackup for the 2+N+2 structure. Once the V-cut path, the governing hole size, and the optimized lamination drawing are confirmed, the mechanical-forming programs, the laser and mechanical drill files, and the sequential press cycle can be released. The board can then proceed through inner-layer imaging, first lamination, laser drilling of the 0.1 mm blind vias, resin plugging, outer-layer processing, and final mechanical forming with the confirmed V-cut. The case illustrates how CAM review of a compact 2+N+2 HDI commonly produces a short set of targeted confirmations—scoring location, drill consistency, and blind-via stackup—that together place the design inside process capability without altering the layer count, material, or surface finish.
