Greetings, and welcome to the Kulicke and Soffa 2018 First Fiscal Quarter Results Call. At this time all participants are in a listen-only mode. (Operator Instructions) As a reminder, this conference is being recorded. It is now my pleasure to introduce your host, Joseph Elgindy, Director of Investor Relations and Strategic Initiatives for Kulicke and Soffa. Joseph, you may begin.
Thank you, Garren. Welcome, everyone, to Kulicke and Soffa's first fiscal quarter 2018 conference call. Joining us on the call today is Fusen Chen, our President and Chief Executive Officer; and Lester Wong, our General Counsel and Chief Financial Officer.
For those of you who have not received a copy of today's results, the release as well as the latest investor presentation are both available in the Investor Relations section of our website at investor.kns.com. In addition to historical statements, today's remarks will contain statements relating to future events and our future results. These statements are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Our actual results and financial condition may differ materially from what is indicated in those forward-looking statements.
For a complete discussion of the risks associated with Kulicke and Soffa that could affect our future results and financial condition, please refer to our recent SEC filings, specifically the 10-K for the year ended September 30th, 2017.
I would now like to turn the call over to Fusen Chen for the business overview. Please go ahead, Fusen.
Thanks, Joe. This quarter, we booked a $105 million charge specifically related to the impact of Tax Cuts and Jobs Act of 2017. Due to this large charge and our ongoing trend to further expand our market, drive share gains and the improved overall profitability, we had supplemented our earnings release with non-GAAP financial metrics. Lester will provide some additional information shortly regarding our non-GAAP approach.
Going forward, our remarks will refer to GAAP results unless noted. For the December quarter, we started out fiscal 2018 with strong results. We delivered $213.7 million of revenue, way above guidance; gross margin of 46.3% and the operating income of $38.6 million.
Excluding the impact of tax reform and our other non-GAAP items, non-GAAP diluted EPS was $0.54. This operational performance was stronger than our expectations a few months ago and dramatically stronger than our trailing December quarter average, largely due to favorable semiconductor-related industry condition and also the slightly earlier-than-anticipated recognition of revenue associated with automotive-related shipment from prior periods.
Our significant exposure to positive trends in advanced packaging, automotive, flash memory, LED, in addition to industry's ongoing capital intensity, are anticipated to continue driving strong operating performance through fiscal 2018.
Much of our incremental earnings were driven by our capital equipment segments while Aftermarket Products and the Service segment, APS, performed in line with our aggressive trends. The strength from capital equipment was driven by strong demand primarily for our ball bonding, wedge bonding and the wafer label packaging offering. Our ball bonding business was up 10%