Nested if statement in sum function in SQL Server2005

The phenomenon and background of the problem

Want to watch 【MouldDetail】 Pass through SUM Function query column 【 Production quantity 】 Of 2 results
1、 Total quantity of production quantity SUM( Production quantity ）, Completed
2、 Historical data of production quantity （ To eliminate SUM( Production quantity ) in <0 That's all ）, But the statement is SUM(IF( Production quantity >0, Production quantity ,0) Has been an error .

Table structure ：

My sentence is ：
select models , Die No ,SUM( Production quantity )' Total quantity ',SUM(IF( Production quantity )>0, Production quantity ,0)' The historical data ' from MouldDetail GROUP BY models , Die No
SUM(IF( Production quantity )>0, Production quantity ,0)' The historical data ' There are always errors reported here , It is no problem to remove this paragraph .
The error message is ：
news 156, Level 15, state 1, The first 1 That's ok
keyword 'IF' There are grammar errors nearby .
news 102, Level 15, state 1, The first 1 That's ok
',' There are grammar errors nearby .
Please help us find out what the mistake is ？