To provide a thin printed wiring board which can deal even with high density mounting of electronic components and double-sided mounting by suppressing warpage.
The printed wiring board 1 has a substrate 7 where a copper foil pattern 6 is formed on an insulating substrate 5, and resists 10 and 11 formed on the surface 8 and the backside 9 of the substrate 7, respectively. The resist 11 on the backside 9 is made thicker than the resist 10 on the surface 8. In the heat-up record of a reflow process when an electronic component is mounted, shrinkage force of the resist 11 excels the shrinkage force of the resist 10, and the printed wiring board 1 begins to warp concavely to the backside 9. Warpage of the printed wiring board 1 itself is suppressed by offsetting the force of warping concavely to the backside 9, and the force of the printed wiring board 1 to warp concavely to the surface 8 side due to the own weight of the printed wiring board, or the weight of the electronic component or the coefficient of linear expansion of the electronic component.
COPYRIGHT: (C)2007,JPO&INPIT
NAKANISHI SEISHI
FUJIHASHI YOSHIKUNI
Hiroki Naito
Daisuke Nagano