how to solve the solder joints not shiny?
It is a myth that solder joints should be shiny, and the surface appearance does not tell you anything about the quality of the electrical connection.

There are many things that can effect the shinyness of the joint, including but not limited to:  type of metal used, type of flux used, age of the flux, soldering iron temp, how long it was at an elevated temp, how quickly it cooled down, how evenly it cooled down, etc.

When evaluating the appearance of a solder joint I look for these things:


Did the solder properly wick or wet the mating surfaces?
Does the solder look even or consistent in how it flowed over the joint?


That's it!  If I want to be extra sure I will sometimes push sideways on a pin of a TSOP or similar inverted gull-wing style chip with a very fine dental pick.  If the pin moves then it wasn't soldered correctly.