Molybdenum Targets and Molybdenum Electrodes in Photovoltaic Cell Processing

In the photovoltaic industry, molybdenum appears on two process lines at the same time: thin-film deposition on the back of solar cells, and electrodes for melting photovoltaic glass. Both are called molybdenum, but delivery form, purity criteria and acceptance methods differ greatly. Clarifying the concepts before purchasing and process discussions saves considerable rework.

Molybdenum on Two Process Lines

Molybdenum targets are used in magnetron sputtering to deposit molybdenum atoms onto a substrate as a thin film, serving the electrodes and barrier layers of solar cells. Molybdenum electrodes are used to pass current into glass furnaces for electric heating, serving the melting of photovoltaic glass. One exists as a thin film inside a vacuum chamber, the other serves long term in a high-temperature melt; their failure modes are entirely different.

The customer bases also differ. Targets serve cell manufacturing and coating lines, electrodes serve glass furnaces and equipment builders. Procurement channels, technical language and quality documents each form a separate system, and mixing the concepts leads both quotation and acceptance astray. When buying both product types from the same supplier, contract numbers and drawing numbers should be managed separately to avoid shipment mix-ups; the technical agreement should also state whether the delivery condition is blank, semi-finished or finished.

Purity and Structure of Molybdenum Targets

Film resistivity and adhesion are affected by target structure. Grains that are too coarse cause uneven sputtering rates and surface nodulation, while insufficient density can generate particles during sputtering that land on the substrate as defects. The bonding method between target and backing plate and the void ratio of the bond layer affect heat dissipation, which in turn limits the usable sputtering power.

Acceptance usually reviews composition analysis, density and grain size results rather than dimensional tolerances alone. Reprocessing and recycling of targets must also be agreed: whether spent targets are returned, how the backing bond layer is removed and how reclaimed material is graded all affect the long-term purchasing cost. Treating spent targets as scrap gives a low book unit price but not necessarily a low total cost.

Grain orientation and texture also affect sputtering uniformity. Manufacturers use different processing routes, so targets of the same purity may differ in sputtering rate and nodulation tendency; trial verification is more reliable than reports alone.

Dimensions and Consumption of Molybdenum Electrodes

Electrodes carry current in the glass melt for long periods and the tip gradually wears. Diameter and length tolerances affect installation and sealing, and straightness affects the consistency of insertion depth. Operators care whether the consumption rate is stable, because it determines maintenance intervals and spare-part planning.

The installation method also affects service. Sidewall insertion requires coordination with water jackets and sealing structures, while bottom installation must consider the risk of glass melt leakage. The choice of sealing material and the tightening sequence often cause more problems than the electrode itself. Consumption rate also depends on position: an electrode of the same specification installed in the hot spot zone and in the fining zone may differ markedly in life, so purchase quantities should be estimated by zone.

Easily Confused Terms

• Applying target purity specifications to electrodes while ignoring high-temperature strength and corrosion resistance.
• Evaluating electrodes by film thickness or resistivity, where the metric does not match the application.
• Treating molybdenum powder, molybdenum blanks and finished parts as one item, leaving the delivery condition unclear.
• Comparing prices by weight while ignoring machining allowance and inspection cost.

On standards, electrode products are controlled under YS/T 1312-2019 Molybdenum Electrodes; molybdenum rod follows ASTM B387 / GB/T 17792; molybdenum plate and discs follow ASTM B386 / GB/T 3876, with acceptance based on the certificate of quality and measured records.

The table is a general comparison; specific purity grades, dimensions and inspection items vary with the application and are typical values or reference ranges, subject to actual operating conditions and the contract. Writing both acceptance standards into a single technical agreement easily leaves inspection items missing or duplicated.

Information to State When Requesting a Quotation

Writing the requirement as a checklist before requesting a quotation is far more efficient: application, atmosphere, temperature, dimensions, inspection items and packaging. With these six stated clearly, the supplier can propose an executable plan. Application determines the material route, atmosphere and temperature determine grade and structure requirements, and dimensions and inspection determine machining and inspection hours.

For targets, also state substrate size, bonding method and spent-target return requirements; for electrodes, state furnace type, installation method, current density and maintenance window. The more complete the information, the closer the quotation is to actual cost and the fewer subsequent changes.

Division of Work between Purchasing and Engineering

Target purchasing is usually led by the coating process and quality departments, focused on sputtering stability and film properties; electrode purchasing is usually led by the furnace or equipment department, focused on installation dimensions and service life. The two lines speak different technical languages, and centralized purchasing easily mixes specifications.

A safer approach is to establish separate technical agreements and supplier lists, unifying only the commercial terms. Applying target purity criteria to electrodes, or electrode dimensional tolerances to targets, will create inspection disputes.

Differences in Testing and Acceptance

Targets are commonly tested for density, grain size and composition, while electrodes are more focused on dimensions, straightness and surface defects. Sampling positions and judgment rules differ, so one sampling ratio cannot serve both. Acceptance should specify that sampling covers both ends and the center, so that a report does not represent only a local area. Test reports should state the sampling position, test method and acceptance basis; reporting only a pass without the inspection scope makes it impossible to judge whether the report represents the whole lot.

The photovoltaic supply chain is cost-sensitive, but losses from material mismatch usually exceed the unit-price difference. Understanding the difference between the two molybdenum products is a shared task for process and purchasing. Putting the application at the top of the inquiry form makes the rest of the conversation much smoother.