Plated half-hole PCB module manufacturing
Castellated Hole PCB Modules
Castellated hole PCB module manufacturing succeeds when plated half-hole geometry, edge routing, surface finish, stencil design, and host-board lands are reviewed as one release package. YourPCB is a good fit when the buyer needs a solder-down module that can pass edge inspection before it becomes a carrier-board assembly problem.
0.2-6.0 mm
board thickness range from site capabilities
2.5 mil
minimum trace and space capability
0.15 mm
minimum mechanical drill capability
ISO 9001
quality system reference used across YourPCB
What This Service Covers
A castellated module uses plated holes cut through the board edge so the remaining half barrels act as solderable side pads. The concept is simple, but the manufacturing sequence is not forgiving: drilling, copper plating, solder mask, surface finish, profiling, depaneling, and assembly inspection all affect the same edge. For general background, compare the module structure with a printed circuit board and with surface-mount technology. The buyer should treat the module as both a PCB and a future SMT component.
The nearest YourPCB pages cover broader board fabrication, SMT assembly, stencil control, and prototype assembly. This page is narrower. It focuses on the failure point that those pages only touch indirectly: whether the module edge remains solderable, inspectable, and dimensionally useful after the plated holes are routed into castellations.
Scope includes FR-4, Rogers, polyimide, and other module boards that fit YourPCB PCB capability ranges: up to 32 layers, 2.5 mil trace or space, 0.15 mm mechanical drill, and 0.2 mm to 6.0 mm board thickness. Out of scope are connector systems that must be repeatedly unmated in service, blind quoting without drill data, or any RF performance claim that has not been defined by the buyer's layout, material, stackup, and test method.
Why Castellated Modules Fail in Production
Castellated modules usually fail from tolerance stacking, not from one dramatic defect. A 1.27 mm pitch edge can look practical in CAD, then lose solderable copper when drill registration, plating thickness, routing offset, solder mask clearance, and panel-tab cleanup all move in the wrong direction. The module may pass bare electrical test and still create weak or bridged solder joints on the carrier board.
A typical RFQ scenario is a 25 mm by 18 mm wireless module with 36 castellated pads, ENIG finish, 1.0 mm finished board thickness, and a host board that will be assembled in the same SMT line as 0402 passives and a fine-pitch microcontroller. The commercial risk is not only the module price. If the module pad geometry is released without the carrier footprint and stencil strategy, the first 200 assemblies can become a solder-bridge sorting job.
"For castellated modules, I want the module Gerbers and the carrier land pattern in the same review. If the factory only sees the small board, it cannot judge the solder fillet, paste volume, or rework risk that the buyer will see during SMT."
HZ
Hommer Zhao
Technical Director, YourPCB
Capability Focus Areas
Half-Hole Edge DFM
We review drill size, annular ring, edge routing, and final pad geometry so the castellation keeps enough copper after profiling.
Module-to-Carrier Fit Review
The module edge and host-board land pattern are checked together because solder fillet, stencil volume, and placement tolerance decide yield.
Surface Finish Selection
ENIG, OSP, HASL, immersion silver, and immersion tin are reviewed against solderability, storage life, edge wetting, and inspection needs.
Panel and Depaneling Control
Castellated edges are sensitive to tab position, router direction, copper tearing, and burr control, so the panel plan is part of the quote review.
SMT Assembly Handoff
For assembled modules, BOM, XY data, stencil notes, and test requirements are aligned before the module is treated as a solder-down component.
Inspection-Ready Release
First articles can be reviewed for edge copper quality, solder wetting, AOI visibility, microscope records, and electrical continuity on key nets.
Technical Specification Review
| Best-fit products | RF modules, IoT modules, sensor boards, power modules, daughtercards, programming adapters |
| Supported PCB materials | FR-4, Rogers, polyimide, aluminum-backed designs when the structure fits |
| Site capability reference | Up to 32 layers, 2.5 mil trace or space, 0.15 mm mechanical drill |
| Common edge pitch range | 0.8 mm to 2.54 mm, reviewed by pad width and routing tolerance |
| Surface finish options | ENIG, OSP, HASL, immersion silver, immersion tin |
| Assembly review | Stencil aperture, host-board footprint, placement tolerance, AOI or microscope checks |
| RFQ files | Gerber or ODB++, NC drill, fabrication drawing, BOM, XY data, carrier footprint |
The table is a release checklist, not a promise that every geometry is automatically buildable. A castellated edge should be reviewed against the real module outline, carrier-board pad pattern, and assembly process before the buyer locks the purchase order.
Castellated Holes vs Other Interconnect Choices
| Option | Best fit | Main tradeoff |
|---|---|---|
| Castellated edge pads | Permanent low-profile modules with visible solder joints | Requires tighter edge DFM and stronger SMT footprint review |
| Pin headers | Simple prototypes and hand-soldered adapter boards | Adds height, connector cost, and manual assembly variation |
| Board-to-board connectors | Removable or serviceable daughtercards | Higher BOM cost and mechanical stack height |
The practical decision is serviceability. Castellated pads are a strong choice when the module is meant to stay soldered to the product. If the buyer expects field replacement, frequent debug swaps, or connector-cycle testing, a connectorized design is often the better engineering choice despite the added cost.
Process Timeline
1
Release Package Review
We check Gerbers, NC drill data, outline files, fabrication notes, and quantity targets before pricing the module. The first review looks for missing edge notes, unclear half-hole dimensions, and conflicts between module pitch and host-board solder lands.
2
Castellation Geometry Check
Drilled hole diameter, copper annular ring, route path, solder mask opening, and pad pitch are reviewed together. A small module can fail if the routing process removes too much plated barrel or leaves burrs that interfere with solder wetting.
3
Material and Finish Decision
The factory plan ties FR-4, Rogers, polyimide, copper weight, board thickness, and finish to the real use case. ENIG is often preferred for flat solder-down module pads, but the best finish depends on storage, assembly, and inspection requirements.
4
Prototype and First Article Inspection
Prototype modules are checked for edge quality, pad geometry, solderability, and fit to the carrier footprint. When assembly is included, first articles should include visible edge-joint inspection and electrical test on the nets that carry power, RF, reset, and programming signals.
5
Repeat Build Control
After the first release, the important control is revision discipline. Panel notes, routing direction, finish, stencil data, and inspection criteria should remain tied to the approved module revision so repeat lots do not rediscover the same edge-quality risks.
Applications
- Wireless and RF modules that need solder-down shielded or antenna-connected edges
- IoT sensor modules where a low profile beats header pins or sockets
- Power modules that need stable board attachment and visible edge fillets
- Programming or debug adapters that mount to a product carrier board
- Embedded compute daughtercards where module replacement is not a service requirement
- Medical, industrial, and robotics electronics that need controlled module release records
Quote Package Checklist
A quote package for castellated hole PCB modules should remove interpretation from the edge. Send the fabrication data, module drawing, and assembly context together so the factory can price the actual build rather than a generic small PCB.
- Gerber or ODB++ files with current revision control
- NC drill files showing plated holes before edge routing
- Module outline, finished thickness, copper, and finish notes
- Castellation pitch, pad width, solder mask clearance, and keepouts
- BOM, XY data, and assembly drawing if the module is populated
- Carrier-board footprint, stencil notes, and test expectations
- Any IPC-A-600 or IPC-A-610 workmanship class expectation
Buyer FAQs
What is a castellated hole PCB module used for?
A castellated hole PCB module is used when a small circuit board must solder directly onto a larger carrier board like an SMT component. The plated half-holes create edge solder pads that can be inspected after reflow, which helps RF modules, IoT radios, power modules, sensor boards, and programming adapters avoid separate board-to-board connectors. Most buyers choose this structure when the module needs 0.8 mm to 2.54 mm edge pitch, repeatable alignment, and a lower profile than pin headers or sockets.
How should I specify castellated holes in a PCB RFQ?
Specify castellated holes with the finished board thickness, plated hole diameter before routing, final half-hole location, edge pitch, copper plating expectation, surface finish, solder mask clearance, and panel tab strategy. A useful RFQ also includes Gerber or ODB++ data, NC drill files, fabrication drawing notes, and the carrier-board land pattern if assembly is planned. Calling out IPC-A-600 visual expectations and the intended SMT reflow process helps the factory review burr, copper smear, and solderability risk before quotation.
My module has 1.27 mm pitch castellations. Is that manufacturable?
A 1.27 mm pitch castellated module is usually manufacturable when the pad width, drilled hole size, routing path, and edge clearance leave enough copper after profiling. The risk is not pitch alone; it is the combined tolerance stack between drill registration, copper annular ring, routing accuracy, and solder mask clearance. For dense 1.27 mm or 1.0 mm pitch edges, send the carrier-board footprint during DFM so the module pads and host PCB lands can be checked together before the first stencil is cut.
Should I choose castellated holes or a board-to-board connector?
Choose castellated holes when the module should be low profile, soldered permanently, visually inspectable, and lower cost at modest pin counts. Choose a board-to-board connector when the module must be removable, replaced in service, or mated through repeated cycles. Castellated edges reduce connector BOM cost, but they transfer alignment, solder fillet, rework, and host-board pad design into the SMT process. For 20 to 80 edge pads, the cost and height benefits often justify the extra DFM review.
Can castellated hole modules be assembled with normal SMT reflow?
Yes, castellated hole modules can be assembled with normal SMT reflow when the host-board land pattern, stencil aperture, module coplanarity, and placement tolerance are reviewed as one system. The module behaves like a large odd-form SMT component, so solder paste volume and edge fillet visibility matter. For first articles, buyers should ask for AOI or microscope inspection on the edge joints and functional test on key nets. Heavy modules may need placement support or fixture review before production.
What defects should buyers watch on plated half-hole PCB edges?
Buyers should watch for copper burrs, exposed laminate fibers, plating pullback, rough routed edges, mask slivers, incomplete solder wetting, and pad-to-pad bridging after reflow. Many defects trace back to weak sequencing: drilling, copper plating, profiling, and final finish must protect the half-hole wall instead of tearing it open. Inspection should include edge-view microscopy on first articles and solder-joint review after assembly, especially when the module uses ENIG pads and 1.0 mm to 1.27 mm pitch.
Related Services
Custom Circuit Board Service
Use this page when the larger board needs stackup, copper, finish, and mechanical feature control beyond the module edge.
SMT PCB Assembly
Use this page when the castellated module must be placed and reflowed onto a host PCB with other surface-mount components.
PCB Stencil Service
Use this page when solder paste volume on the carrier pads needs review before first articles are built.
PCB Assembly Prototype
Use this page when the first module and carrier build needs fast validation before repeat production.
Get a Quote for Castellated PCB Modules
Send Gerbers, drill data, module outline notes, BOM, XY data, and the carrier-board footprint. YourPCB can review half-hole geometry, surface finish, stencil risk, and inspection needs before the first build.
Send Module Files