Electronic-Grade Thiourea Dioxide (TDO) - Buyer FAQ (33 Questions)

This page collects the 33 questions buyers ask most often about electronic-grade thiourea dioxide (TDO), covering product identity, purity and metallic impurities, quality documents, packaging and transport, price and lead time, samples and compliance, and international trade and logistics. Specifications follow our technical data sheet and the batch COA.

1. Product Identity & Grades

What is the chemical name, CAS number and molecular formula of your product? Is it the same as thiourea?

Product: Thiourea Dioxide (TDO). CAS 1758-73-2; molecular formula CH4N2O2S; white crystalline powder. It is NOT thiourea (CAS 62-56-6, CH4N2S) — the names are similar, but the structure, reducing properties and applications differ, so never mix them in quoting or in use.

What exactly does “electronic grade” mean? How does it differ from industrial-grade 99%?

“Electronic grade” is not just “99% assay”. The real value is quantified control of trace metals (Na/Fe/Cu/Cr, etc.), moisture, insolubles, particles and lot-to-lot consistency; industrial grade typically only specifies assay plus a coarse Fe≤10 ppm. Our standard electronic grade (total metals ≤10 ppm): assay ≥99.5%, per-element ICP-MS. We recommend buyers verify against their own process spec rather than the label alone.

What grades do you offer? Which should I order first?

Bands can be customised by total metallic impurities: ≤30 ppm (basic), ≤10 ppm (recommended) and ≤2 ppm (high-end custom). We suggest starting with the ≤10 ppm band (assay ≥99.5%): it differentiates clearly from industrial grade without pushing cost out of commercial range. The ≤2 ppm band is best committed only after process qualification.

2. Purity & Routine Specs

What is the assay and how is it measured?

The standard electronic grade assays ≥99.50%, measured by redox titration. We report the test method, LOQ and actual values, not just “conforms”.

What are the moisture, insoluble matter and residue-on-ignition specs?

Standard electronic grade: moisture ≤0.05% (Karl Fischer), residual thiourea ≤0.02%, insoluble matter ≤0.01% (gravimetric), residue on ignition ≤0.01%. Methods: assay=redox titration, moisture=Karl Fischer, organics=HPLC, trace metals=ICP-MS, particle size=laser diffraction, insolubles=gravimetric.

3. Metals & ICP-MS

Which metals do you control — “total heavy metals” or per-element limits?

We do not write a vague “Heavy Metals ≤10 ppm”. We control per element via ICP-MS: Na, Ca, Al, Cu, Zn ≤1 ppm each; Cr, Co, Cd, Sb ≤0.5–0.1 ppm; total metals ≤10 ppm. Per-element limits are what electronics customers actually need.

What method do you use for metal impurities? What is the LOQ? ppm or ppb?

ICP-MS; units per element in ppm (basic electronic grade) or ppb (high-end custom). We provide method, MDL/LOQ and basis (product weight vs solution).

Do you run ICP-MS on every batch? Can you provide per-element actual values?

Yes. Every batch ships with a per-element ICP-MS report with actual values and detection limits, not just pass/fail. We can supply multi-lot COA history and statistics for the same specification to demonstrate batch consistency.

4. Quality Documents & Traceability

Do you provide a COA with every shipment? What does it contain?

Yes, a lot-specific COA with every shipment: lot number, manufacture date, retest date, quantity, appearance, assay, moisture, thiourea, insolubles, residue on ignition, conclusion, QA release and signature/stamp.

Can you issue a COA in our format? What other documents can you provide?

Yes, customer-formatted COA available. Per batch we can also provide: ICP-MS trace-metal report, SDS, batch traceability record; additional reports (e.g. third-party) on request.

Do you have full traceability? How long are retention samples kept?

Full traceability (raw material → production → testing → packaging → shipment) by lot. Retention sample periods are agreed in the contract; the default is one year.

5. Packaging, Storage & Transport

What is the packaging material? Is it moisture-proof and metal-contamination-proof?

Standard: 100g/500g/1kg HDPE bottles, 5kg clean packaging, 20/25kg double-layer moisture-proof packaging; customizable. Thiourea dioxide is hygroscopic, so packaging focuses on moisture and secondary metal contamination; inner liner / nitrogen / cleanroom filling available on request.

What pack sizes are available? Can you customize?

Sample (100g/500g/1kg), pilot (5kg), production (20/25kg); custom packaging available.

What are the storage conditions and shelf life?

Keep sealed, cool, dry and out of direct light, not above 25 C, away from moisture, heat sources, strong oxidisers and strong alkalis. Shelf life is 12 months from the date of manufacture under the recommended conditions.

6. Price, MOQ & Lead Time

What is the price? Why is electronic-grade thiourea dioxide more expensive than industrial grade?

Electronic grade cannot be priced by adding a fixed percentage to industrial grade. The extra cost comes from raw-material purification, heavy-metal removal, multi-stage filtration, ultrapure water and clean packaging, plus ICP-MS, ion chromatography, particle-size and batch-consistency testing, COA and customer qualification. Quotations are tiered by customer specification, test scope and order size, and priced by destination; the quotation we issue governs.

What is the MOQ for sample, pilot and production?

MOQ is negotiated case by case. Sample, pilot and production quantities are agreed separately.

What is the lead time, capacity and supply stability?

Lead time is confirmed with the order. Scheduling depends on specification and batch, and varies with the season; custom specifications take longer. Our thiourea dioxide capacity is 10,000 tonnes per year, with electronic grade scheduled to order.

7. Samples, Certification & Compliance

Do you offer free samples? What tests should customers run to validate it?

Yes. New customers receive a standard free 200 g sample (which can be split into smaller packs) with TDS, COA, ICP-MS report and application note. Larger or custom samples are agreed separately, and where the request warrants it we can reduce sample and freight charges. Recommended validation: precursor stability (UV-vis), film morphology (SEM), defect density (PL/TRPL), Sn oxidation (XPS), device efficiency & stability (MPP tracking).

Do you have ISO certification? Can we do third-party testing/audit? What is your change-control policy?

We hold ISO 9001 and maintain a change-control policy (customers notified in writing before any process/raw-material/site change). Third-party testing and audits are accepted.

8. Logistics & Compliance (extras)

What is the dangerous-goods classification / UN number? Can you export and provide multi-language MSDS and customs documents?

Thiourea dioxide is UN 3341, Class 4.2 self-heating, packing group II, and is not a marine pollutant. All export documents can be provided: commercial invoice, packing list, certificate of origin (CO), COA, MSDS/SDS, DG packaging certificate and dangerous-goods declaration, customisable to the destination.

Does the product meet RoHS / REACH? Can you provide a compliance statement?

RoHS and REACH compliance statements can be issued against the current version of each regulation; the exact scope is set out in the declaration itself.

Are English TDS / COA / SDS / application notes complete?

English TDS, COA, SDS and application notes are all available.

9. Commercial (extras)

Will you sign NDA, quality agreement and annual supply agreements?

We can sign NDA, quality agreements and annual supply agreements, terms negotiated case by case; tiered pricing and volume lock supported.

Can your technical team support DOE, formulation optimization and scale-up validation?

We support dosage DOE, formulation optimization, pilot and scale-up validation, with application-engineer support; the depth of support depends on cooperation stage and order size.

10. Application (extras)

What is the mechanism and literature basis for thiourea dioxide suppressing Sn²⁺ oxidation and passivating defects?

Thiourea dioxide (reported in the literature as formamidinesulfinic acid) acts as a surface-anchoring zwitterionic antioxidant: it suppresses Sn²⁺→Sn⁴⁺ oxidation, lowers defect density and improves film uniformity in all-perovskite tandem devices. The literature (Nature Energy, Sargent group) reports 21.7% for this additive in Sn-Pb single junctions and a certified 24.2% for all-perovskite tandems, with a suggested dosage of 0.1–1.0 mol%. These are literature figures, not our own device results.

What is the current annual capacity, expansion plan and long-term supply commitment?

Annual capacity 10,000 tonnes; expansion plan and long-term supply commitment negotiable.

11. International Trade & Logistics

What payment methods and terms do you accept?

Payment method and credit terms are confirmed in the quotation and the contract. New customers normally pay a deposit plus the balance before shipment; common methods such as T/T or L/C at sight can be discussed, and terms for established and long-term customers are agreed separately.

Which Incoterms do you offer?

Common Incoterms such as EXW, FOB and CIF can be discussed; the port named in the quotation applies.

Can you do OEM / private-label / neutral packaging?

Customer-branded labelling and neutral packaging are available; the minimum order quantity depends on pack size and is confirmed with the order.

Are samples free? Who pays the freight?

New customers receive a standard free 200 g sample; domestic freight is covered by us. International courier charges are assessed by destination and quantity, and where a genuinely large sample quantity is needed we can reduce sample and freight charges. Custom or larger samples are quoted separately and are creditable against a later bulk order.

How is bulk shipped — by sea or air?

Bulk shipments normally go by sea, as FCL or LCL. Thiourea dioxide is UN 3341, Class 4.2 self-heating, so the mode of carriage is subject to carrier acceptance and air freight is normally restricted.

Do you provide export documents and customs clearance?

All export documents available: commercial invoice, packing list, CO, COA, MSDS/SDS, DG packaging certificate, etc., customizable by destination.

How long is the quotation valid?

The validity period, currency and Incoterm are stated on the quotation.