勛圖tv 繚 ENGINEERING GUIDE
Chip on Board Assembly: Die Attach, Interconnect and Protection Planning
Chip on board assembly places a semiconductor die directly into a board-level assembly rather than treating it as an ordinary packaged SMT component. Die attachment, interconnection and protection become explicit parts of the product's manufacturing definition. The exact route must be evaluated from the die and board requirements.
This page helps prepare that engineering enquiry. The die-attach worksheet estimates a geometric adhesive volume from area and bond-line thickness. It does not establish a dispense program, acceptable voiding, bond strength or evidence that a specific COB process is available for the project.
Define the die and interconnection route
Provide the die source, identification, dimensions, pad map and relevant handling requirements. Establish the intended interconnection method and the die supplier's compatibility conditions. Wire bonding and flip-chip approaches have different interfaces; they are not interchangeable generic instructions.
Keep the die's electrical and mechanical requirements separate from those of a packaged device with similar function. Procurement must preserve the approved die revision and supply format. A circuit-equivalent substitution can change pad layout, attachment materials and protection requirements.
Review the board surface as a process interface
The die-attach region and bonding sites need a defined surface and geometry compatible with the selected process. Copper layout, finish, cleanliness, support and nearby topography can affect the operation. A standard PCB finish name alone does not establish bondability for every interconnect method.
Discuss the board fabrication requirements through the PCB manufacturing service while keeping the COB-specific interface requirements in the assembly definition. Any proposed finish or material substitution requires review against the actual die-attach and interconnect process.
| Review item | What to establish |
|---|---|
| Die | Preserve die identity, pad map and handling requirements. |
| Interface | Verify finish and material compatibility for the actual route. |
| Volume | The geometric model does not set allowable voiding. |
| Evidence | Confirm process feasibility and inspection before commitment. |
Estimate die-attach volume without inventing acceptance limits
For a rectangular region, area times bond-line thickness gives a geometric volume. The tool converts micrometers of thickness to millimeters and applies an entered excluded-area fraction. That fraction is a modeling assumption, not an allowed production void percentage.
For a 4 mm by 5 mm region and 30 micrometer bond line, gross volume is 0.60 cubic millimeters. Real dispense quantity may differ because of squeeze-out, shape, material behavior and process losses. Use supplier guidance and representative trials to establish actual settings rather than copying this result into a machine.
Plan attachment, interconnect and protection together
Material cure, die placement and subsequent interconnection must be compatible. The protection system can introduce additional thermal and mechanical effects, so it should be considered before the die is attached. Encapsulation should not conceal an unresolved interconnect or contamination issue.
Keep the sequence documented, including when inspections and electrical checks occur. A protective compound may improve environmental separation while making repair difficult. The intended product disposition must be understood before a process is selected.
COB die-attach volume estimate
COB die-attach volume estimate
Use the current inputs and keep the assumptions
Choose the question you want to resolve before entering numbers. The fields start blank. Load example deliberately if you want to understand the calculation, and keep that example separate from your project record. The example label remains visible after editing; reset the tool before preparing a record from your own data.
Use the displayed units and identify the source of each input. A dimension should refer to the same layer, reference plane and design revision as the other dimensions in the model. An entered limit is your review requirement, not an IPC value supplied by this website. Where a value is unknown, obtain it or preserve the question as open instead of guessing a familiar number.
Read the assumptions with the result. A negative margin is retained so a conflict remains visible. A positive margin only answers the stated mathematical question. It does not establish process capability, compliance, electrical performance or production yield. Checklist statuses are self-reported and do not imply that the underlying evidence has been inspected.
Changing a field invalidates the result and disables its download until you calculate again. The text download contains the current inputs, result and limitations. No CAD file is read, no project data is uploaded and nothing is automatically inserted into Contact. Attach the record manually if useful. You can request a review directly without using the worksheet.
| Input | What to establish before using it |
|---|---|
| Review reference | Connect this worksheet to a nonconfidential design/revision reference. |
| Die attach width 繚 mm | Use the actual released drawing and one dimensional reference. |
| Die attach length 繚 mm | Use the actual released drawing and one dimensional reference. |
| Bond-line thickness 繚 micrometers | User-defined geometric assumption; cure shrinkage and squeeze-out excluded. |
| Excluded area fraction 繚 percent | Geometric coverage assumption, not an allowed void criterion. |
Optional cost comparison from your own allowances
Use a quotation or a clearly labeled internal assumption for each input. Keep the quantity, construction and inspection scope the same when comparing alternatives. This uncalibrated planning model adds entered values; it contains no current market rates and does not issue a 勛圖tv quotation. You can contact the team without completing it.
Entered assembly cost scenario
Specify evidence at each irreversible step
Define what verifies the die-attach condition, the interconnect and the finished protected assembly. The appropriate methods depend on the selected construction and product requirements. A photograph of an encapsulated board is not proof of internal bond quality or qualification.
Use representative samples and agreed acceptance methods for development work. Distinguish a process feasibility trial from a qualified recurring production route. Images on this page provide board and package context; the original diagrams explain COB concepts and are not records of a 勛圖tv COB production line.
Prepare a feasibility and cost discussion
Supply die documentation, board files, intended quantity, environment and verification requirements. State whether materials and methods are already qualified or still open. Confirm process availability and scope with 勛圖tv before assuming the enquiry is equivalent to a normal SMT order.
The optional budget tool adds allowances you provide for the defined scope. Die supply, fixtures, process development, interconnection, protection and inspection can be separate elements. A useful proposal makes those responsibilities and exclusions explicit rather than quoting only the geometric adhesive quantity or board area.
Separate feasibility development from recurring production
A chip-on-board enquiry should identify whether the product is still choosing a process or already has an approved manufacturing definition. The evidence and commercial scope differ substantially. Development may need representative trials, materials review and specialized interconnection work before a repeatable production proposal can be established.
Keep the die supply and board interface controlled. Die revision, surface condition, pad arrangement and handling can influence attachment and interconnection. The board finish and local geometry must be compatible with the selected route. A generic PCB specification is not enough if it omits the features that make the die attach or bonding operation possible.
Define the order in which evidence is collected. Some interfaces become difficult to inspect after encapsulation, so the relevant checks must occur earlier. Exterior protection quality, internal connection quality and electrical behavior are separate questions. Choose methods that address the actual requirement instead of assuming one image or one test proves everything.
Review material interactions and product conditions together. Cure exposure, mechanical constraint, contamination sensitivity and environmental protection can affect the design. A material with a useful individual property is not automatically compatible with the complete assembly. Retain the supplier guidance and the conditions demonstrated by representative work.
Agree what happens to nonconforming units. The practical repair route may differ from ordinary packaged-component rework. If replacement or removal is not approved, record the intended disposition before production. This avoids a later cost comparison relying on an unverified assumption that every assembly can be repaired.
For a 勛圖tv feasibility discussion, provide the die documentation, board data, intended quantity and required verification. Ask for confirmation of the proposed process scope and availability. The photographs on this page are contextual archive images, and the diagrams are explanatory. Neither should be interpreted as evidence that the exact COB construction has already been manufactured or qualified.
Standards, source context and limits
The references below support the stated package, design or process context. Apply a component manufacturer's guidance to its named device or family and confirm the exact drawing revision. A supplier application note is not a universal manufacturing rule, and a public standards scope is not the complete controlled standard.
Agree the governing documents, revision basis, acceptance requirements and exceptions with the responsible engineering and quality teams. The official IPC revision table is useful for checking document status; it does not by itself resolve a project's contractual requirements. This page does not reproduce paid normative tables or claim certification.
Archive photographs illustrate relevant boards, components or assembly activity. They are not proof of the current equipment inventory or a completed qualification for your project. The explanatory drawings and worked examples are original teaching aids. Confirm actual process availability and the proposed inspection scope during the project review.