When a metal-dome keypad overlay and the customer's PCB are sourced separately, joint sample approval should identify one traceable assembly combination: the revisions of the overlay, PCB, housing or actuator, how they are assembled, what is checked, and who approves it. Separate component approvals from two suppliers do not replace confirmation that this combination works together. This article concerns ordinary, non-safety-related equipment interfaces, not emergency stops, safety interlocks or complete machine-control design.
In its official report dated October 26, 2026, Zoomlion described the release of its 9DX hybrid tractor that day at the China International Agricultural Machinery Exhibition. The company stated that it had developed the digital chassis, core components and control system itself. We use the reported release and the company's own account, without extending its performance claims or inferring the equipment's keypad construction or a Baoshengda supply relationship.
For an equipment manufacturer developing its own control board and buying the keypad overlay separately, this development context raises a procurement coordination question: if the board is managed internally and the overlay comes from an external supplier, who organizes approval of the assembled sample? The suggestions below apply to the reader's own project, not to the procurement arrangements of the equipment in the news.
Name a coordinator in the purchase requirements
List delivery of overlay samples and assembly confirmation using the customer's PCB as separate deliverables. The overlay supplier can provide samples against the agreed drawing. Assembly confirmation also needs the matching PCB, housing or actuator, and the project's assembly and inspection conditions. Purchasing should name a project owner to collect these inputs and arrange for the parties to review the same sample combination and record, rather than letting each supplier say yes based on its own samples.
If the customer cannot yet provide the matching PCB, state that this review covers only the overlay checks that can be completed. Leave assembly compatibility pending. Do not mark joint sample approval complete and then bury a missing mating part in a note. The project can agree on attendance, remote review or shipment of samples; an on-site meeting is not always required.
Identify the combination, not just the overlay part number
The table is a suggested purchasing record, not a universal industry acceptance form. It should lead back to the actual mating parts. Photographs are supplementary: materials, contact finishes and internal features that cannot be seen still need controlled documents and identifiable physical samples.
| Combination record item | Identity to record | Who supplies or confirms it |
|---|---|---|
| Metal-dome keypad overlay | Part number, artwork and construction revisions, sample ID, and the layers or components included in this supply | Overlay supplier provides the information; project owner checks the purchasing boundary |
| Customer PCB | Board number, revision, physical sample ID and current contact-related information | Customer or nominated board supplier provides it; the overlay supplier should not infer it |
| Housing, support and actuator | Actual revisions, locating and fastening methods, and any temporary substitutes | Responsible design or assembly party confirms them |
| Assembly and checks performed | Combination ID, assembly basis, inspection items and criteria, record ID and uncovered items | Agreed executing party records them; approving party checks applicability |
| Approval decision | Approved combination, limitations or open actions, approver and date, and where each party keeps its sample or record | Personnel with the relevant project authority approve it; a supplier's verbal response is insufficient |
For example, an internal combination record could link an overlay sample ID, a PCB sample ID and the assembly-part revisions. This illustrates a record format, not a Baoshengda customer case. Confirmation forms sent to both suppliers would reference that same record. If one party changes a document later, the other can identify the interface that needs review.
Why the mating parts need to be available together
Snaptron's dome assembly design guidance explains that PCB contacts, venting and actuation need to be considered with the stack-up, and that a dome can behave differently in a finished assembly than in a standalone test. Purchasing should therefore not treat a dome document as approval of its fit with the customer's board and housing. The project's design and verification owners still need to define the construction and criteria.
Snaptron's dome-array attachment guidance describes preloaded domes on an adhesive carrier attached to a PCB and notes that prototype tolerances can differ from the final design. If joint sample approval uses a temporary board, manual positioning or substitute support, record the differences and let the project owner decide what further confirmation is needed. Approval of that temporary combination should not automatically cover the production combination. The source explains its own product format; it does not establish that Baoshengda uses the same materials or process.
Clarify mating-part dependencies when requesting a quotation
Shenzhen Baoshengda Technology Co., Ltd.'s integrated keypad information calls for checking the customer's existing housing, main board and other parts, and confirming component supply, assembly and testing separately (original Chinese source). Ask the parties to state the scope of overlay-only samples, what the customer must provide for assembly review, whether tooling or assembly checks are priced separately, and which approval milestone cannot be completed while parts are missing. Ask whether PCB purchasing, firmware or complete-machine verification is included in the overlay quotation; unlisted scope and lead times remain to be confirmed.
If only markings and window coverage are needed, discuss the actual scope of a graphic overlay or keypad overlay (Chinese source); a surface-only part does not include switch circuitry. The dome overlay discussed here needs the customer's PCB. Having domes alone does not make it a complete membrane switch that already includes the customer's circuitry and control functions. The cover shows the front and separated rear layers of an existing sample, not a completed joint approval for this article.
For deciding whether a functional requirement belongs in component procurement, see HMI customization and component purchasing scope (Chinese). For the documents needed after the combination is approved, see sample-to-production handover (Chinese). Use the project contact page to provide the overlay drawing, PCB and housing revisions, available samples and missing items. Ask the supplier to identify what can be confirmed and which mating parts are needed before arranging joint sample approval.