When a board is too small, not rectangular, or has parts overhanging its edge, it needs to be panelized, with rails for the conveyor to grip, fiducials and tooling holes. Boards in a panel are usually joined in one of two ways: V-cut for straight lines on boards thick enough, with a cut from the top and bottom leaving about one-third of the thickness; or breakaway tabs with mouse bites for curved outlines or thin boards. The trouble usually comes from parts too close to the break line: one manufacturer recommends parts at least 3 mm from the V-cut groove, and at least 5 mm for stress-sensitive parts such as ceramic capacitors, BGAs, crystals and connectors; other sources also give 5 mm but measure it differently (from the board edge, a fixing point or the cutting zone); and capacitors are better oriented parallel to the board edge. For depaneling, one consultant says hand breaking is probably a bad method; every mechanical method stresses the board edge, parts and joints, and laser has no mechanical stress, each with its trade-offs; ceramic capacitors cracked during depaneling are often missed by AOI and functional test, so settle the panel before releasing the design. This article covers how boards in a panel are joined, rails and part clearance, and how to choose a depaneling method after assembly; panel utilization calculations at the board fab and depaneling machine comparisons are outside its scope. It is divided into 5 stages:
- Stage ① Why panelize, and what goes on the rails: small boards, outlines, overhanging parts; rails, fiducials, tooling holes.
- Stage ② V-cut or tabs with mouse bites: look at the outline, the thickness and what sits beside the break line.
- Stage ③ How far parts sit from the break line, and how to place them: general and stress-sensitive parts, orientation, slots beside the break line.
- Stage ④ Choosing a depaneling method: hand break, V-cut wheel, router, punch, saw, laser.
- Stage ⑤ Settle before release, and verify: cracks may not show in test; measure strain, then section; revisit the panel for volume production.
Each stage below covers how to do it, with how JIAHON can help where it applies; sources and exceptions are at the end. This describes the general case; individual cases still need their own assessment.
Figure 1. The five stages of PCB panelization (illustration): ① why panelize (small or non-rectangular boards; rails for the conveyor; fiducials and tooling holes) → ② how to join (V-cut for straight lines and enough thickness; mouse bites for curves and thin boards; mixed, judged line by line) → ③ part clearance (general parts back from the line; stress-sensitive parts further; parallel orientation and routed slots) → ④ depaneling method (hand break; mechanical methods all stress; laser has no mechanical stress) → ⑤ settle and verify (settle the panel before release; cracks may not show in test; measure strain and section).
Stage ①: Why panelize, and what goes on the rails
- Small boards: on one EMS provider’s line, boards smaller than 50 mm × 50 mm must be panelized, or they cannot be gripped and conveyed reliably (Source 1).
- Outlines and overhanging parts: round or irregular boards have no straight edge for the conveyor, so they are arrayed with breakaway areas; boards with connectors overhanging the edge also need rails for protection (Source 1).
- Rails: on the two longer sides of the panel, commonly 5 to 10 mm wide, with the conveying direction marked in the files (Source 1).
- Fiducials: at least three on the whole panel, placed asymmetrically so it cannot be loaded rotated 180°; two to three on each board, on opposite corners; local fiducials beside fine-pitch BGAs and QFNs (Source 1).
- Tooling holes: commonly 3.0 to 4.0 mm, non-plated, on opposite corners of the rails (Source 1).
- Thin boards: boards under about 0.8 mm, flex boards, irregular boards with large cutouts and very long panels often need a carrier for support (Source 1).
Source 1 notes that figures not labeled as its own line’s are common industry practice.
Figure 2. Panel layout and V-cut cross-section (illustration based on Source 1, not to scale): fiducials (asymmetric), rails on the long sides, tooling holes on opposite corners, ceramic capacitors kept back from the line, V-cut lines, and tabs with mouse bites for curved outlines. In the V-cut section, one cut from the top and one from the bottom leave about one-third; when the board is too thin, what remains cannot hold, so tabs with mouse bites are used instead.
How JIAHON can help:
- For custom fixtures, JIAHON’s Process & Fixture Design page says: “What standard products can’t solve, let us evaluate, design and build.” Send photos or drawings, and our engineering department will reply on whether and how it can be made.
Stage ②: V-cut or tabs with mouse bites
- Look at the outline first: rectangular boards with straight separation lines can use V-cut; curves, notches and irregular outlines use tabs (Source 1).
- Then the thickness: V-cut uses a 30° or 45° blade to cut grooves from both sides, leaving about one-third of the thickness; below about 1.0 mm, what remains is too thin to survive conveying and reflow, so use tabs instead; some lines set the limit at 1.2 mm (Source 1).
- How deep to cut: another source says 30% to 40% of the thickness is cut from both sides, without saying whether per side or in total (Source 5); a consultant, speaking from memory, says IPC’s recommendation is about one-third from each side (Source 4).
- Then what sits beside the line: if large ceramic capacitors or BGAs are beside the separation line, switch to tabs or rearrange the layout (Source 1; “rearrange” is this article’s compilation).
- Mouse bites: tabs commonly carry a row of three or five holes of about 0.5 mm; small panels use three holes; breaking leaves a jagged edge, so if the board must fit an enclosure or rail, note on the drawing whether it should be routed smooth (Source 1).
- No traces across tabs, and no parts right beside either end of a tab (Source 1).
- Methods can be mixed: V-cut on straight edges, tabs on curved or crowded edges, judging each separation line on its own (Source 1).
Stage ③: How far parts sit from the break line, and how to place them
- General parts: part bodies at least 3 mm from the V-cut groove (Source 1).
- Stress-sensitive parts at least 5 mm: ceramic capacitors 1206 and larger, large packages such as BGAs, crystals and ceramic resonators, and connectors (Source 1). A passive component maker writes that board makers’ design standards usually require ceramic capacitors to be 5 mm from the board edge (Source 2); a capacitor maker writes that within 5 mm of the board edge or a fixing point is a stress zone (Source 3); depaneling machine makers mostly recommend at least 5 mm from the cutting zone (Source 4). These 5 mm figures are measured from different references (board edge, fixing point, cutting zone).
- Capacitor orientation: ceramic capacitors parallel to the board edge are usually better than perpendicular (Source 2).
- Slots beside the break line: routing a slot along the break line first reduces stress during depaneling; a capacitor maker says slotting reduces the stress on capacitors by about 50% (Sources 2, 3).
- Tabs too: when tabs are broken, adjacent parts take more stress, so keep parts back from tabs on the same principle (Source 1).
- Don’t oversize pads: smaller pads also reduce capacitor stress by about 50% (Source 3).
The consultant in Source 4 says the 5 mm recommendation is about capacitors, but applies to parts such as QFNs and array packages too. The 50% figures are the capacitor maker’s statements, without test conditions.
Stage ④: Choosing a depaneling method
- Hand break: a consultant in an industry Q&A program says hand breaking is probably a bad method among those they have seen; even with a correct V-cut, breaking by hand puts unnecessary stress on the board, and a common problem is resistors and capacitors too close to the break area cracking (Source 4). An article in a medical electronics magazine says some high-reliability medical electronics assembly has moved from methods that bend the board (hand bending, scoring, rolling-blade cutting) to punching and routing (Source 2).
- V-cut wheel: a round blade, like a pizza cutter, cuts through the remaining material along the V-cut, stressing parts and joints, especially near the board edge (Source 5).
- Router: the outline is routed before assembly, leaving tabs, and separated after assembly; it can cut curves, but needs space set aside and makes the panel less rigid (Source 5).
- Punch: each board needs its own die, which is inflexible, and punching force may bend or deform the board edge (Source 5).
- Saw: a high-speed blade generates heat and debris at the cut (Source 5).
- Laser: no mechanical stress and high positional accuracy (within 50 µm for CO₂ lasers and 25 µm for UV lasers); it can cut boards with parts very close to the cut line, and more rigid-flex boards are being depaneled by laser (Source 5).
- All mechanical methods stress the board: the mechanical methods above stress the board edge and the parts and joints near the cut, and may delaminate the edge or leave voids around the glass fibers (Source 5).
Figure 3. Depaneling methods: every mechanical method stresses the board edge, parts and joints; laser has no mechanical stress (illustration based on Sources 4 and 5; not a ranking of stress). Mechanical: hand break (the consultant calls it probably bad), V-cut wheel (parts near the edge stressed), punch (edge may deform), router (needs space set aside), saw (heat and debris). Laser: no mechanical stress, high positional accuracy, can cut with parts close to the line, increasingly used for rigid-flex.
Stage ⑤: Settle before release, and verify
- Settle before release: the panel constrains both bare board fabrication and assembly, so review it before releasing Gerbers; once boards are cut, changing it means cutting them again (Source 1).
- Let the factory lay it out: if the assembler proposes the panel, it can be laid out directly to match their rail range, router bit diameter and depaneling equipment (Source 1).
- Cracks may not show in test: ceramic capacitors cracked during depaneling cannot be seen inside by AOI, often pass functional test, and fail in the field after shipment (Source 1); automated test, functional test and X-ray all struggle to catch such cracks (Source 3).
- How to confirm afterward: use dye and pry, or cross-sectioning (Source 1).
- Measure strain: measure on the line at every step where the assembled board is handled or stressed; strain gauges are an effective tool (Source 2).
- Revisit for volume production: prototypes and small lots value flexibility, with fewer boards per panel; volume production values material use and line rhythm, and larger panels sag more, so recheck the support (Source 1).
How JIAHON can help:
- JIAHON’s engineering department can help review whether a PCB design is easy to manufacture, including panelization.
Sources and limits
Sources: Source 1: an EMS provider’s blog article (August 2026). Source 2: a passive component maker’s article in a medical electronics magazine (2007). Source 3: a capacitor maker’s technical article (undated; the text mentions 2010). Source 4: a Q&A from an industry consultant program (undated; comments from 2010 to 2016). Source 5: a company’s technical article on laser depaneling (undated; references up to 2015). JIAHON material: the scope of JIAHON engineering support and the Process & Fixture Design page. The full texts of IPC standards on panelization or depaneling were not read; “about one-third from each side” is an IPC recommendation a consultant cited from memory, without naming the document.
Where sources stand: Source 1 is an EMS provider promoting its own line and engineering services; Sources 2 and 3 are component makers, and Source 3 promotes its own products; Source 5’s topic is laser depaneling and leans toward promoting it; Source 4 is a consultant’s spoken Q&A.
Where figures differ: the three sources give V-cut depth differently (leave about one-third, cut 30% to 40%, about one-third from each side); follow your board maker’s capability and the board thickness. The 3 mm and 5 mm clearances are recommendations for different parts, not a conflict. 50 mm × 50 mm is that company’s line limit; the 50% reductions from slotting and smaller pads are the capacitor maker’s statements without test conditions; with other boards, parts or equipment, rely on your own validation. Source 2 dates from 2007, when depaneling equipment differed; Sources 3, 4 and 5 are undated, so treat their concepts as reference and go by current equipment capability.
This is a general summary, not a restatement of any standard, an endorsement of any board maker, assembler or component maker, or a promise about your product or process; follow your product specifications, your board maker’s and assembler’s specifications, and your own validation.