search for charater "="

Hi there
I'm using awk to search the character equal "=" and replace it with
space character " " in file1. The result is redirected to another
file2.

----------------file1-------------------
field1="data1"after there is some data...
field2="data2"after there is some data...
field3="data3"after there is some data...
field4="data4"after there is some data...
-----------------end_file1---------------------

I used this
awk 's/=/ ' file1 >> file2

but I get this error

awk: s/=/TEST
awk:     ^ unterminated regexp


I want to have the next file
----------------file2-------------------
field1 "data1"after there is some data...
field2 "data2"after there is some data...
field3 "data3"after there is some data...
field4 "data4"after there is some data...
-----------------end_file2---------------------

how to indicate that I'm searching for character and not for an
unterminated regular expression?
Thanks for your help.