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                                                                  EXHIBIT (A)(5)

                          Offer to Purchase for Cash
                    All Outstanding Shares of Common Stock
 
                                      of
                              AG Associates, Inc.
 
                                      at
 
                              $5.50 Net Per Share
 
                                      by
 
                          MIG Acquisition Corporation
                         a wholly owned subsidiary of
 
                         STEAG Electronic Systems GmbH
 
 
    THE OFFER, WITHDRAWAL RIGHTS AND PRORATION PERIOD WILL EXPIRE AT 12:00
MIDNIGHT NEW YORK CITY TIME, ON FRIDAY, FEBRUARY 19, 1999, UNLESS THE OFFER IS
                                   EXTENDED.
 
 
To Our Clients:
 
  Enclosed for your consideration are an Offer to Purchase, dated January 22,
1999 (the "Offer to Purchase"), and a related Letter of Transmittal (which, as
amended or supplemented from time to time, together constitute the "Offer")
relating to the offer by MIG Acquisition Corporation, a Delaware corporation
("Purchaser") and a wholly owned subsidiary of STEAG Electronic Systems GmbH,
a corporation organized under the laws of the Federal Republic of Germany, to
purchase all outstanding shares of common stock, without par value (the
"Shares"), of AG Associates, Inc., a California corporation (the "Company"),
at a price of $5.50 per Share, net to the seller in cash, without interest,
upon the terms and subject to the conditions set forth in the Offer. Parent is
a wholly owned subsidiary of STEAG Aktiengesellschaft, a corporation organized
under the laws of the Federal Republic of Germany. Also enclosed is the letter
to shareholders of the Company from Dr. Arnon Gat, Chief Executive Officer and
Chairman of the Company, together with a Solicitation/Recommendation Statement
on Schedule 14D-9 filed with the Securities and Exchange Commission by the
Company. We are (or our nominee is) the holder of record of Shares held by us
for your account. A tender of such Shares can be made only by us as the holder
of record and pursuant to your instructions. The Letter of Transmittal is
furnished to you for your information only and cannot be used by you to tender
Shares held by us for your account.
 
  We request instructions as to whether you wish to have us tender on your
behalf any or all of the Shares held by us for your account, upon the terms
and subject to the conditions set forth in the Offer.
 
  Your attention is invited to the following:
 
    1. The tender price is $5.50 per Share, net to the seller in cash,
  without interest.
 
    2. The Offer is being made for all outstanding Shares.
 
    3. The Board of Directors of the Company has unanimously approved the
  Merger Agreement and the transactions contemplated thereby, has determined
  that each of the Merger Agreement and the transactions contemplated thereby
  are fair to, and in the best interests of, the Company and the Company's
  shareholders, and recommends that the Company's shareholders accept the
  Offer and tender their Shares to Purchaser.
 
    4. The Offer and withdrawal rights will expire at 12:00 Midnight, New
  York City time, on Friday, February 19, 1999, unless the Offer is extended.
 
    5. The Offer is conditioned upon, among other things, (i) there being
  validly tendered and not withdrawn prior to the expiration of the Offer
  such number of Shares which would constitute not less than 90% of the
  Shares then outstanding (the "Minimum Condition"), and (ii) the expiration
  or termination of
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  any applicable waiting periods under the Hart-Scott-Rodino Antitrust
  Improvements Act of 1976, as amended. The Offer also is subject to the
  other terms and conditions described in the Offer to Purchase.
 
    6. In the event that more than 50% of the Shares then outstanding are
  tendered pursuant to the Offer and not withdrawn, but less than 90% of the
  Shares then outstanding are acquired by Purchaser pursuant to the Offer and
  the Stock Option described in the Offer to Purchase, Purchaser will waive
  the Minimum Condition and amend the Offer to reduce the number of Shares
  subject to the Offer to 3,095,294 Shares or such greater or lesser number
  of Shares as equals 49.9% of the Shares then outstanding (the "Revised
  Minimum Number") and, if a greater number of Shares is tendered into the
  Offer and not withdrawn, purchase, on a pro rata basis, the Revised Minimum
  Number of Shares (it being understood that Purchaser shall not in any event
  be required to accept for payment, or pay for, any Shares if less than the
  Revised Minimum Number of Shares are tendered pursuant to the Offer and not
  withdrawn at the expiration of the Offer).
 
    7. Tendering shareholders will not be obligated to pay brokerage fees or
  commissions or, except as provided in Instruction 6 of the Letter of
  Transmittal, stock transfer taxes with respect to the purchase of Shares by
  Purchaser pursuant to the Offer.
 
  If you wish to have us tender any or all of your Shares held by us for your
account, please so instruct us by completing, executing and returning to us
the instruction form contained in this letter. An envelope to return your
instructions to us is enclosed. If you authorize the tender of your Shares,
all such Shares will be tendered unless otherwise specified in your
instructions. Your instructions should be forwarded to us as soon as possible
so that we will have ample time to tender your Shares on your behalf prior to
the expiration of the Offer.
 
  In all cases, payment for Shares tendered and accepted for payment pursuant
to the Offer will be made only after timely receipt by BankBoston, N.A. (the
"Depositary") of (i) the certificates evidencing the tendered Shares (the
"Share Certificates"), or a timely Book-Entry Confirmation (as defined in the
Offer to Purchase) with respect to such Shares, (ii) a Letter of Transmittal
(or facsimile thereof), properly completed and duly executed, with any
required signature guarantees, or, in the case of a book-entry transfer
effected pursuant to the procedure set forth in the Offer to Purchase, and
(iii) any other documents required under the Letter of Transmittal.
 
  The Offer is made to all holders of Shares solely by the Offer to Purchase
and the related Letter of Transmittal and any supplements or amendments
thereto. Purchaser is not aware of any state where the making of the Offer is
prohibited by administrative or judicial action pursuant to any valid state
statute. If Purchaser becomes aware of any valid state statute prohibiting the
making of the Offer or the acceptance of Shares pursuant thereto, Purchaser
will make a good faith effort to comply with such state statute. If, after
such good faith effort, Purchaser cannot comply with such state statute, the
Offer will not be made to (nor will tenders be accepted from or on behalf of)
the holders of Shares in such state. In any jurisdiction where the securities,
blue sky or other laws require the Offer to be made by a licensed broker or
dealer, the Offer shall be deemed to be made on behalf of Purchaser by one or
more registered brokers or dealers licensed under the laws of such
jurisdiction.
 
                                       2
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                       Instructions With Respect to the
       Offer to Purchase for Cash All Outstanding Shares of Common Stock
 
                                      of
 
                              AG Associates, Inc.
 
                                      by
 
                          MIG Acquisition Corporation
 
                         a wholly owned subsidiary of
 
                         STEAG Electronic Systems GmbH
 
  The undersigned acknowledge(s) receipt of your letter and the enclosed Offer
to Purchase, dated January 22, 1999, and the related Letter of Transmittal
(which, as amended or supplemented from time to time, together constitute the
"Offer") in connection with the offer by MIG Acquisition Corporation, a
Delaware corporation and a wholly owned subsidiary of STEAG Electronic Systems
GmbH, a corporation organized under the laws of the Federal Republic of
Germany, to purchase all outstanding shares of common stock, without par value
(the "Shares"), of AG Associates, Inc., a California corporation.
 
  This will instruct you to tender the number of Shares indicated below (or,
if no number is indicated below, all Shares) that are held by you for the
account of the undersigned, upon the terms and subject to the conditions set
forth in the Offer.
 
    NUMBER OF SHARES TO BE                              SIGN HERE
          TENDERED:*                      -------------------------------------
 

                                          -------------------------------------
SHARES: _______________________
 
                                                Signature(s) of Holder(s)
 
Dated: __________________, 1999           Name(s) of Holder(s):
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* Unless otherwise indicated, it will be assumed that all Shares held by us
  for your account are to be tendered.
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1404-LT-99
