Most of the times many job applications are shortlisted only on basis of mail(You need to only send a letter requesting for the vacant job and the Xeroxes of your certificates etc.). In this type of jobs, certificates do matter a lot since you are directly shortlisted based on the papers you sent.
In a campus interview, Face to face interview….. Certificates do make a better impression on the interviewers but carry a lot less weightage, because companies usually seek for a student who has thorough knowledge in the subject, rather than a student who has just spent the whole college life searching for internships and collecting certificates.
So, My suggestion would be to concentrate more on your studies and try to gain in depth knowledge. Try to find some interships of your area of interest. Best time to find interns usually are during the summer vacations.