Packaging and testing houses Advanced Semiconductor Engineering (ASE) and Siliconware Precision Industries (SPIL) both saw their core business revenues miss their guidance of 2-5% sequential growth and an up to 3% on-quarter decrease, respectively, in the fourth quarter of 2012.

ASE has announced consolidated revenues of NT$56.01 billion (US$1.9 billion) for the fourth quarter of 2012, up 14.3% sequentially. Excluding sales generated by EMS subsidiary Universal Scientific Industrial (USI), ASE saw fourth-quarter sales of its core ATM (assembly test and material) business increase by a mere 1.5% on quarter to NT$34.4 billion.

ASE previously said that core operations would post a shipment rise of 3-5% sequentially in the fourth quarter of 2012, buoyed by strong demand for mobile chips.

Financial data provided by ASE also showed that a strengthened NT dollar affected the company's sales performance in the fourth quarter. Sales of ASE's core ATM operations denominated in US dollars registered a larger 4% sequential increase in the quarter.

Consolidated revenues at SPIL slipped 4.2% on quarter to NT$16.15 billion in the fourth quarter of 2012. SPIL estimated previously that fourth-quarter sales would see flat growth or a slight drop of up to 3% sequentially.

Market watchers attributed the two packagers' disappointing fourth-quarter sales results to a slowdown in orders starting December from their clients, including handset IC designers MediaTek and Spreadtrum, as well as PC chip vendors Marvell and Intel.

In December, sales of ASE's core business experienced an 8.8% on-month decrease, while SPIL posted a 12.95% decline.