Assembly and retention guide
Adhesive Magnets: Specification, Selection and Sourcing Guide
Direct answer: An adhesive magnet is a magnet-and-joint system. Specify the finished magnet surface, adhesive identity and thickness, production substrate, surface preparation, peel and shear loading, temperature and fluids, application pressure and dwell, pole orientation, and representative retention test before release.
What “adhesive magnet” should mean on an OEM drawing
For this guide, the term means a discrete or rigid permanent magnet supplied with a defined adhesive-backed face or integrated into an adhesive-bonded assembly. It does not mean a flexible magnetic sheet, craft strip, generic glue recommendation, or a universal stock product. The flexible route has a separate adhesive magnetic sheet guide.
Start by defining the magnetic function and the mechanical retention function separately. The pole face must produce the required field or holding result, while the adhesive joint must retain the part through handling, assembly, service, and fault conditions.
Engineering Evidence · EM-ASM-01 · Revision A
Adhesive-backed rigid magnet joint review
Treat the magnet, adhesive, substrate, load direction, environment, assembly process, and final release test as one controlled joint.
| Joint layer | Input to define | Evidence to retain |
|---|---|---|
| Magnet | Material, dimensions, coating, flatness, edges, magnetization, and pole face | Approved drawing and finished-part condition |
| Adhesive | Exact system, thickness, carrier, liner, age, storage, and processing guidance | Approved identity and controlled application window |
| Substrate | Material, surface energy, texture, paint, cleanliness, curvature, and stability | Actual production substrate and preparation method |
| Load | Shear, peel, cleavage, impact, vibration, magnetic attraction, and orientation | Worst-case joint geometry and retention boundary |
| Environment | Application temperature, pressure, dwell, heat, fluids, humidity, and cycling | Representative aged and environmental test |
| Release | Magnetic function, mechanical retention, packaging, traceability, and changes | Assembly-level acceptance record |
Peel and shear are not interchangeable
A large flat joint may carry load well in one direction and fail quickly when a corner is peeled or a rigid part rocks. Define where magnetic attraction, gravity, impact, cable load, vibration, removal force, assembly tooling, and user handling act. If the product can be pried, struck, or repeatedly removed, test that behavior directly.
Surface condition controls the joint
The production substrate may be painted metal, coated steel, glass, polymer, composite, or another finished surface. Texture, curvature, release agents, oil, dust, moisture, plasticizer, cleaner residue, and low surface energy can change adhesion. Use the actual substrate and controlled surface preparation rather than a clean laboratory coupon.
The magnet’s own coating and finished surface also matter. Coating damage, contamination, edge chipping, flatness, and adhesive chemistry can affect retention and corrosion risk.
Adhesive thickness changes the magnetic gap
Adhesive can conform to surface texture and distribute stress, but it also adds a controlled thickness between the magnet and the assembly. If the magnetic circuit crosses that interface, the added gap can reduce useful field or holding force. Include liner, adhesive, coating, substrate, and compression assumptions in the tolerance stack and magnetic test.
Temperature and fluids affect the complete assembly
Review the adhesive application temperature and process, dwell before loading, service heat, cycling, humidity, condensation, oil, cleaning agents, fuels, plasticizers, and other chemicals. A magnet material may remain acceptable while the adhesive, coating, substrate, or joint geometry does not.
What to include in the RFQ
- Magnet drawing, material intent, coating, flatness, edge condition, magnetization, and required pole face.
- Exact production substrate, surface finish, texture, curvature, coating, and preparation method.
- Adhesive preference or required function, thickness limit, liner, application process, and dwell.
- Load direction, impact, vibration, removal, magnetic attraction, and safety or backup retention.
- Continuous and peak temperature, humidity, fluids, cleaners, UV, storage, and service life target.
- Prototype quantity, annual demand, packaging, traceability, and representative test method.
Use finished-condition tolerances, custom assembly review, and inspection planning. Send the actual joint inputs through the RFQ path.
Boundary: adhesive brand, joint strength, temperature range, substrate compatibility, service life, feasibility, price, MOQ, lead time, and acceptance criteria remain specific to the proposed magnet, adhesive, substrate, process, load, environment, and validation plan.
Frequently asked questions
What is an adhesive magnet?
For an OEM assembly, it is a discrete or rigid permanent magnet supplied with a defined adhesive-backed face or bonded into a controlled joint. The magnet and the adhesive retention system must be specified together.
What is the best adhesive for a magnet?
There is no universal best adhesive. Selection depends on the magnet surface, substrate, surface preparation, peel and shear load, temperature, fluids, gap, assembly process, dwell, and required validation.
Why do adhesive-backed magnets fall off?
Possible causes include contamination, low-surface-energy or textured substrate, wrong preparation, peel loading, insufficient pressure or dwell, heat, fluids, coating failure, curvature, impact, or an unrepresentative test.
Does adhesive thickness affect magnetic performance?
It can. Adhesive and coating thickness may add to the magnetic gap or change alignment and flatness, reducing useful field or holding force when the circuit crosses that interface.
What should be sent for an adhesive magnet RFQ?
Send the magnet drawing and pole face, coating, exact production substrate, surface finish and preparation, load directions, adhesive or process preference, environment, quantities, packaging, and retention test.