Monthly Archives: June 2010

Exposed copper of HASL analysis and treatment

Posted by on June 21, 2010 No comments

As you know, the HASL is the most popular PCB surface treatment,exposed copper maybe be coursed by this method.

HASL is that input the PCB in molten solder (63SN/37PB), then use hot air to blows off the excess solder in the surface and metal-based inner hole of printed circuit board to get a smooth, uniform and also bright solder plated layer. After HASL surface treatment of printed circuit board the plated layer should be bright and uniform integrity, good weldability, without nodules and half-wetting,plated layer is complete no exposed copper.

After HASL, pad surface and the metal-based inner hole are exposed copper is an important test of finished product defects, also is the one of main reasons of HASL rework. please see the below several reasons for exposed copper:

1. Pad surface dirty, contaminated with residual solder pad.
2. Pre-treatment is not enough, coarsening bad.
3. Flux activity is not enough.

We should control the technology of exposed copper of HASL surface treatment, reduce the Rework and poor circuir boards, ensure the quality of products.

PCB to prevent warping

Posted by on June 19, 2010 No comments

How to prevent the PCB warping? This is the most improtant in the PCB manufacturing preocess.

1. Why is flat circuit board requirement

In the automation plug line, if PCB isn’t flat will cause mispositioning, components can not plug in to the board of the hole and surface mount pad, and even crashing automatically installed machine. After components installed on board, component pins are difficult to cut neatly. Board can not be fitted to the chassis or the machine’s outlet, so, board assembly factory is also very troubled.

2. Warpage standards and test methods

According to the U.S. IPC-6012 (1996 Edition) <<Rigid Printed Boards and performance specifications>> for the maximum allowable surface mount PCB warpage and distortion of 0.75%, other 1.5% of various board permitted. Compare to IPC-RB-276 (1992 Edition) to improve on the requirements of surface mount PCB. Currently, the electronic assembly factory agree with, regardless of double or multi, 1.6mm thickness, is usually 0.70 to 0.75%, and for SMT, BGA’s board, demand is 0.5%.
 
3. Warping board processing:

As in our factory, PCB in the final test will be 100% flatness inspection. Failure of the board who will be singled out, into the oven at 150 degrees and bake under the weight of 3 to 6 hours, and under the weight of natural cooling. And relieving the board out, check in for smoothness, this would save parts of the board, some boards need to bake for two to three times the pressure to leveling.