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1. Why STDF exists. Every semiconductor test program produces huge volumes of measurement data — thousands of tests across thousands of dies per wafer, across many wafers and lots. STDF gives the whole industry one common container so that data from a Teradyne, Advantest, Cohu/Xcerra or any other tester can be read and analyzed with the same tools. Without a shared format, every fab and OSAT would need custom parsers for every machine.

2. It is a binary format. STDF is not human-readable text. It is a compact binary stream of variable-length records, each with a header (record type + sub-type) followed by typed fields. This keeps files small and fast to write on the tester, but it means you cannot simply open an STDF file in Notepad — you need software that understands the record structure. The most widely used version today is STDF V4.

3. The main STDF V4 record types. An STDF file is a sequence of records that describe the test run from start to finish:

• FAR — File Attributes Record: identifies the file as STDF and its version.
• MIR / MRR — Master Information / Master Results: lot ID, part type, tester name, program name, start and end time.
• WIR / WRR — Wafer Information / Wafer Results: per-wafer start, finish, and yield summary.
• PIR / PRR — Part Information / Part Results: marks the start and end of testing for a single die/part, including its X-Y coordinate and final hard/soft bin.
• PTR — Parametric Test Record: one numeric measurement (value, units, low/high limits) for a single test.
• FTR — Functional Test Record: pass/fail result of a functional (vector) test.
• MPR — Multiple-Result Parametric Record: several measured values from one test (e.g. pin arrays).
• HBR / SBR — Hardware Bin / Software Bin Record: counts of parts per bin.
• TSR — Test Synopsis Record: per-test execution counts, fail counts and timing.

4. Where STDF files come from. They are generated automatically by the ATE during production test at wafer sort (probe) and final test. Fabs, OSATs (assembly & test houses) and IDMs collect these datalogs continuously and use them for yield monitoring, quality control and failure analysis.

5. What you extract from STDF. Once parsed, an STDF datalog can drive a wide range of analyses: wafer maps (bin maps and value maps painted on the wafer), yield and bin Pareto, histograms and trend/scatter charts with spec limits and ±σ bands, capability metrics like Cpk, outlier screening such as PAT (Part Average Testing), measurement-system studies like Gauge R&R, and wafer-to-wafer or lot-to-lot correlation.

6. Why you need a dedicated STDF tool. Because STDF is binary and can contain millions of records per lot, opening and cross-analyzing many files by hand is impractical. DLOG reads STDF V4 record by record, loads many files at once, and turns raw datalogs into wafer maps, charts and PDF / Excel / image reports in a few clicks — fully offline on your own PC. Try it free for 6 months →

STDF is a binary format, so a text editor cannot open it — you need an STDF viewer or STDF analysis tool. Install DLOG on Windows, drag your .stdf / .std file into the window, and DLOG parses the STDF V4 records and immediately shows the datalog, test list, bin summary and wafer map. No tester or ATE software is required.

Yes. DLOG is free for 6 months from first launch with every feature enabled — STDF viewing, wafer maps, yield, Cpk, histograms, PAT and Gauge R&R. No credit card and no account are required, so you can use it as a free STDF viewer and analyzer while you evaluate it.

Open the STDF file in DLOG and export. DLOG converts STDF datalogs to Excel (.xlsx), CSV and PDF, and can also export charts and wafer maps as images. This lets you turn raw binary STDF test data into a spreadsheet or a finished report without writing an STDF parser.

Yes. DLOG loads many STDF files in a single batch and merges them into one analysis, so you can compare lots, wafers and retests, stack wafer maps, and build a combined yield and Cpk report across the whole group instead of opening each datalog one by one.

Yes. DLOG builds wafer maps, die maps and bin maps directly from the STDF wafer records (WIR/WRR, PRR, HBR/SBR) — colored by soft bin, hard bin or by a parametric test value. Multiple wafers can be stacked to reveal repeating spatial failure patterns.

DLOG computes Cp, Cpk, mean, sigma, min/max and yield automatically for every test in the STDF file, using the limits stored in the PTR/MPR records. Results appear as a statistics table plus histograms, box plots and trend charts, and can be exported to Excel or PDF.

Any tester that writes STDF V4. STDF is the industry-standard datalog format across virtually all ATE (automatic test equipment), so DLOG works with STDF produced during wafer sort, probe test and final test regardless of which vendor's tester created it.

DLOG reads STDF V4 (Standard Test Data Format) datalogs produced by ATE / testers, and builds wafer maps, yield, charts and reports from them.

No. DLOG runs fully offline — your STDF files and yield data stay on your PC and are never sent to any server.

All features are free for 6 months from first launch. No credit card and no account required.

A license is bound to a single PC via its Activation ID. Reformatting or resetting the same PC keeps working (if a hardware change such as a new motherboard alters the Activation ID, email us for a free re-issue); a different PC needs a new license. See the License Agreement for details.

Because a full-featured 6-month trial lets you evaluate first, purchases are generally final — but we always help if activation fails. See the Refund Policy.

No. Prices exclude tax; any VAT or sales tax required in your country is added at checkout. Your payment is processed by Lemon Squeezy, our Merchant of Record, who issues your invoice and remits applicable taxes.

No. DLOG works completely offline and needs no account.

Yes. DLOG generates the Activation ID on the PC itself, so you can copy it to any internet-connected device to purchase, then type the license code into DLOG on the offline PC. No internet connection is needed on that PC.

DLOG is a native Windows application built for large STDF V4 datalogs. You can load many multi-site STDF files at the same time and stack them into combined wafer maps and statistics. Actual speed depends on your PC's CPU, memory and disk.