Laser hermetic welding uses laser welding to create a package boundary with a specified resistance to gas leakage. The distinction from general laser welding is primarily the product requirement and the process built around it: a joint may need to carry a load, while a hermetic closure must also control leakage through the complete enclosure.
These are overlapping categories. Conventional laser welding can produce hermetic joints when the design, process and verification support that result. Conversely, putting a laser inside a glovebox does not automatically make every weld hermetic. The laser hermetic sealing overview explains the equipment routes; this guide focuses on what changes in an engineering specification.
Start with the acceptance requirement
A general laser-welded assembly may be accepted against strength, dimensions, penetration, appearance or fatigue performance. A hermetic package adds a defined leak-test requirement, often together with constraints on its internal atmosphere and the thermal exposure of enclosed components.
Write the requirement before choosing the machine. Identify the permitted leakage, units, test conditions, product condition at testing and applicable procedure. Do not substitute a detector sensitivity figure for a package acceptance limit. Likewise, a label such as sealed or airtight needs an associated verification method before it becomes an actionable manufacturing requirement.
| Design question | General laser welding | Laser welding for a hermetic closure |
|---|---|---|
| What must the joint achieve? | The drawing may prioritize strength, dimensions or appearance | The package must also meet a specified leakage requirement |
| Must the path be continuous? | Separate spots or intermittent seams may be appropriate | Every part of the intended seal boundary must be closed |
| What atmosphere matters? | Shielding is selected for weld quality | Both the weld environment and the enclosed atmosphere may matter |
| What defects are relevant? | Acceptance depends on structural and functional requirements | A through-connected defect can create a leak even if the joint carries load |
| What must be tested? | The joint and assembly characteristics specified by the drawing | The full package boundary as well as the weld characteristics |
This comparison is a specification framework, not a claim that every general-purpose weld has loose requirements. Many structural applications have demanding qualification rules of their own.
Design a complete seal boundary
Draw the intended gas barrier on a section of the assembly. Follow it around the lid, housing, windows, electrical feedthroughs and any fill ports. Every transition needs a sealing mechanism and a way to verify its performance.
For the laser seam, evaluate joint access, land width, fit-up, local thickness and the location of internal components. A fixture that supports a lid well along straight sides may behave differently at corners. A continuous-looking bead can still contain a local lack of fusion or a connected pore path. Development samples should therefore include the actual seam geometry rather than only convenient straight coupons.
For electronic packages, a closure weld is one part of a system that may already contain other seals. A failed whole-package leak test does not identify the closure seam as the cause without additional localization.
Treat starts, stops and corners as separate process conditions
Straight-line welding settings do not fully describe a closed seam. Consider three additional events:
- At the start, the material and fixture may be relatively cold and the weld pool is still forming.
- At a corner, motion speed or direction may change, altering energy deposited per unit length.
- At closure, the beam returns to material that has already experienced a thermal cycle.
For a pulsed process, pulse timing and motion determine how adjacent fused regions connect. For a continuous process, power, speed and the final termination still require control. Neither approach has a universal overlap or ramp setting that can be transferred safely to every package.
Plan section locations and inspection around these events. If a straight section is acceptable but the closing region leaks, increasing power everywhere may create a new problem without correcting the local transition.
Choose the atmosphere for the material and the package
There are two questions: what protects the hot metal, and what atmosphere should remain inside the completed package? They may lead to different equipment requirements.
Local shielding may be suitable when the full sensitive region can be protected and the internal atmosphere has no additional requirement. A glovebox laser welding system provides an enclosed environment for material handling and sealing. A vacuum laser welding system addresses applications requiring a qualified low-pressure process route.
Specify the atmosphere at the point and time that matter to the part. Chamber readings alone do not establish the final gas composition inside a cavity. Material transfer, trapped spaces, cleaning residues and the closure sequence can influence the result. Any oxygen, moisture or pressure target should come from the product and process qualification, rather than a generic equipment claim.
Include the contents in the thermal plan
A successful seam can coexist with damaged internal components. Before trials, identify temperature-sensitive elements, their distance from the seam, and any permitted exposure limits supplied by the product design team.
Use representative assemblies to evaluate heat accumulation, distortion and component function. Empty housings are useful for early development but do not reproduce every thermal path of a populated package. Fixture contact and clamp force should be documented because they can affect both alignment and heat flow.
Verify weld quality and package leakage separately
Weld inspection and leak testing answer different questions. Cross-sections can reveal fusion and penetration at selected locations. A leak test evaluates gas flow across a boundary under defined conditions. Neither result alone describes every aspect of package reliability.
Use a documented inspection plan that links seam observations, dimensional checks, representative destructive examinations and package leak results to the same part or trial record. The gross-leak and fine-leak comparison explains why a very low helium signal is not sufficient evidence by itself for every sealed package.
A practical equipment specification checklist
Before requesting equipment, provide:
- housing and lid drawings, material grades and surface treatments;
- seal-path geometry, fit-up tolerances and weld access;
- internal components and their thermal limits;
- required sealing atmosphere and handling sequence;
- leak-test method, acceptance criteria and other inspection requirements;
- production volume, loading approach and traceability needs;
- representative parts for process development.
JMLASER uses these inputs to discuss equipment and process configuration. The aim is a process that can repeatedly produce and verify the required package boundary. Selecting a laser power rating alone does not define that process.