John Waters wrote :

>  Hi All,
>
>  I made a number of PCB but the copper trace on all of them got very thin,
>  some are even broken. The followings were what I did:-
>
>  1. The dimension of the positive photoresist coated PCB was 3"x4".
>  2. I put the inkjet printed transparency on top of the PCB and
>  exposed under
>  UV light for 7 minutes.
>  3. I put the PCB into developer solution and used a brush to
>  help removing
>  the photoresist, within less than a minute, all unwanted blue colored
>  photoresist was gone, but I still leave the PCB soaked in the
>  solution for
>  another 2 more minutes,
>  4. The developed PCB was then put into slightly warmed Ferric Chloride
>  solution, again I used a brush to remove the copper until all unwanted
>  copper is cleared, the whole process took about 20 minutes.
>
>  I want to know what causes the problem:-
>  excessive UV-exposure, developed or etched the board too long, Ferric
>  Chloride solution too concentrated, or what?

My suggestion : have a look at the following thread in PICLIST :

[OT]: laser print -> copper board PCB transfer

For me it is the definite solution for homemade PCBs. If you have any doubt
do not hesitate to contact me

Joan

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu