This week, the overall grades of three semiconductor stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Silicon Motion Technology Corporation Sponsored ADR (SIMO) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Silicon Motion Technology is a semiconductor company that designs, develops, and markets semiconductor products for the multimedia consumer electronics market. For Portfolio Grader’s specific subcategory of Sales Growth, SIMO also gets an F. For a full analysis of SIMO stock, visit Portfolio Grader.

Amkor Technology, Inc. (AMKR) is having a tough week. The company’s rating falls from a C to a D. Amkor Technology provides outsourced semiconductor packaging and test services in the United States and internationally. To get an in-depth look at AMKR, get Portfolio Grader’s complete analysis of AMKR stock.

Tower Semiconductor Ltd (TSEM) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Tower Semiconductor, an independent semiconductor foundry, manufactures analog intensive mixed-signal semiconductor devices in the United States, India, the Asia Pacific, Europe, and Israel. The stock gets F’s in Equity, Cash Flow and Sales Growth. For more information, get Portfolio Grader’s complete analysis of TSEM stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.