iPhone 4 no sound from speaker

i have ip4 logicboard with no sound from the speaker.

i have heated it to reflow the weldings and fixed itunes error 1604. Sucessfull restore. maybe i used too much heat? Does anyone know what temp the mainboard can handle before components get busted?

does someone know which chips and resistors to look for?

have multiple logicboards lying around to pick parts from.