High-reliability application printed circuit board assembly QFN assembling and welding pretreatment method
A printed circuit board, pretreatment technology, applied in printed circuits, manufacturing tools, welding equipment, etc., can solve the problems of low reliability of QFN solder joints, prone to false soldering, etc., to shorten the production cycle, uniform tinning, The effect of improving yield and reliability
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[0032] The present invention is further illustrated by specific examples below. However, these examples are only used to illustrate the present invention and not to limit the scope of the present invention.
[0033] Attached with instructions Figure 1~5 , A method for pre-enamelling QFN pads, including the following steps:
[0034] Step 1). Fabrication of a carrier board 4 for pre-painting the QFN chip pad 6 with tin. The carrier board 4 is a composite layer structure. The carrier board 4 is a solder mask layer 9 and an FR-4 ring from top to bottom. Oxygen board 7, copper foil layer 8 and FR-4 epoxy board 7; wherein, the solder resist layer 9 is the layer of printed solder paste 5; this design is to meet the needs of this method, and the carrier board is required to be flat and the surface of the carrier board It is not combined with solder, and the carrier board does not deform during heating up to 245°C, while considering processing convenience, low cost and reusability.
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