Exhibit 4.3

Specimen form of certificate representing Common Stock of Amtech Systems, Inc.

|NUMBER                  |                                                       | SHARES                                 
|----------------------- | ----------------------------------------------------- | ---------------------------------------
|                        |                                                       |                                        
|AS                      |                                                       |                                        
|_______________________ |                                                       | _______________________                
|                        | AMTECH   SYSTEMS, INC.                                |                                        
|                        | INCORPORATED UNDER THE   LAWS OF THE STATE OF ARIZONA |                                        
|                        |                                                       | CUSIP                                  
|                        |                                                       | _______________________                
|                        |                                                       | SEE   REVERSE   FOR CERTAIN DEFINITIONS

THIS CERTIFIES THAT

Is The Owner of

FULLY PAID AND NON-ASSESSABLE SHARES OF THE $.01 PAR VALUE COMMON STOCK OF

AMTECH SYSTEMS, INC.

transferable on the books of the Corporation by the holder hereby, in person or by duly authorized attorney, upon surrender of this certificate properly endorsed or accompanied by a proper assignment.  This certificate and the shares represented hereby are issued and shall be subject to all the provisions of the Articles of Incorporation and the Bylaws of the Corporation, and all amendments thereto, copies of which are on file a t the principal office of the corporation and the Transfer Agent, to all of which the holder of this Certificate by acceptance hereof assents.  This Certificate is not valid unless countersigned by the Transfer Agent.

IN WITNESS WHEREOF, the Corporation has caused the facsimile signatures of its duly authorized officers and its facsimile seal to be hereunto affixed.

Dated:

| |           |  | Amtech Systems, Inc.   Corporate Seal 1981 * Arizona |           | 
| | --------- |  | ---------------------------------------------------- | --------- | 
| |           |  |                                                      |          
| | Secretary |  |                                                      | President

| | COUNTERSIGNED by:                           
| | --------------------------------------------
| | COMPUTERSHARE TRUST   COMPANY, INC. - DENVER
| | TRANSFER AGENT AND   REGISTRAR              



AMTECH SYSTEMS, INC.

TRANSFER FEE:   $15.00 PER NEW CERTIFICATE ISSUED

The following abbreviations when used in the inscription on the face of this certificate shall be construed as though they were written out in full according to applicable laws or regulations:

|TEN COM | -as tenants in common           |  | UNIF GIFT MIN ACT-____Custodial_____
|------- | ------------------------------- |  | ------------------------------------
|TEN ENT | -as tenants by the entireties   |  | _____(Cust)_____(Minor)             
|JT TEN  | -as joint tenants with right of |  | Under   Uniform Gifts to Minors     
|        | survivorship and not as tenants |  | Act_________________________        
|        | in common                       |  | (State)                             

|Additional   abbreviations may also be used though not in the above list.                                  
|-----------------------------------------------------------------------------------------------------------
|___________________________________________________________________________________________________________
|                                                                                                           
|For Value Received, ____________________________________________   hereby sell, assign and   transfer unto 

|PLEASE INSERT SOCIAL   SECURITY OR OTHER   IDENTIFYING NUMBER OF ASSIGNEE | 
|------------------------------------------------------------------------- | 
|                                                                          | 
|___________________________________________                               | 
|                                                                          | 

|                                                                                                                                              
|----------------------------------------------------------------------------------------------------------------------------------------------
|___________________________________________________________________________________________________________                                   
|(PLEASE   PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING SIP CODE, OF ASSIGNEE)                                                               
|                                                                                                                                              
|___________________________________________________________________________________________________________                                   
|                                                                                                                                              
|___________________________________________________________________________________________________________                                   
|                                                                                                                                              
|___________________________________________________________________________________________________________                                   
|Shares of the Common Stock   represented by the within Certificate, and do hereby irrevocably constitute   and appoint                        
|                                                                                                                                              
|___________________________________________________________________________________________________________                                   
|attorney-in-fact to   transfer the said stock on the books of the within-named Corporation, with   full power of substitution in the premises.

|Dated |                                 | 
|----- | ------------------------------- | 
|      | _______________________________ | 

| | __________________________________________________________________________
| | --------------------------------------------------------------------------
| |                                                                           
| | __________________________________________________________________________
| | NOTICE:                                                                   

|Signature(s) Guaranteed.                             | 
|---------------------------------------------------- | 
|                                                     | 
|____________________________________________________ | 

The signature(s) should be guaranteed
by an eligible guarantor institution (Banks, Stockbrokers, Savings and Loan
Associations and Credit Unions with membership in an approved signature
guarantee Medallion Program), pursuant to S.E.C. Rule 17Ad-15.

This certificate also evidences and entitles the holder hereof to certain Rights as set forth in the Rights Agreement,
dated as of May 17, 1999 (the Rights Agreement), between Amtech Systems, Inc. and American Securities Transfer & Trust,
Inc., as Rights Agent, the terms of which are hereby incorporated herein by reference and a copy of which is on file at the
principal offices of Amtech Systems, Inc. Under certain circumstances, as set forth in the Rights Agreement, such Rights
will be evidenced by separate certificates and will no longer be evidenced by this certificate. Amtech Systems, Inc. will
mail to the holder of this certificate a copy of the Rights Agreement, as in effect on the date of mailing, without charge
promptly after receipt of a written request therefor. Under certain circumstances set forth in the Rights Agreement, Rights
issued to, or held by, any Person who is, was or becomes an Acquiring Person or any Affiliate or Associate thereof (as such
terms are defined in the Rights Agreement), whether currently held by or on behalf of such Person or by any subsequent
holder, may become null and void.