
<PAGE>   1

                                                                       EXHIBIT 5

                [BANCBOSTON ROBERTSON STEPHENS INC. LETTERHEAD]

                                  July 1, 1999

Board of Directors
ADFlex Solutions, Inc.
2001 W. Chandler Boulevard
Chandler, Arizona

Members of the Board:

     We understand that ADFlex Solutions, Inc. (the "Company"), Innovex, Inc.
("Acquiror") and Innovex Acquisition Corp. (a wholly owned subsidiary of
Acquiror, "Merger Sub") are proposing to enter into an Agreement and Plan of
Merger (the "Agreement") which will provide, among other things, for the Offer
and the Merger (as such terms are defined below). Under the terms, and subject
to the conditions, set forth in a draft of the Agreement dated June 30, 1999
(the "Draft Agreement"), (i) Merger Sub will commence a tender offer (the
"Offer") to purchase all of the outstanding shares of common stock of the
Company, par value $0.01 per share ("Company Common Stock") at a price of $3.80
per share, net to the seller in cash, and (ii) following the Offer, Merger Sub
will be merged with and into the Company (the "Merger"). Pursuant to the Merger,
the Company will become a wholly owned subsidiary of Acquiror and each share of
Company Common Stock (other than shares of Company Common Stock held in treasury
or owned by Acquiror or any of its subsidiaries or as to which dissenters'
rights have been properly exercised ("Dissenting Shares")) shall be converted
into the right to receive $3.80 in cash or any higher price paid for each Share
in the Offer, without interest. The terms and conditions of the Offer and the
Merger are set out more fully in the Agreement.

     You have asked us whether, in our opinion, the cash consideration to be
paid in the Offer and the Merger is fair from a financial point of view and as
of the date hereof to the "Holders of Company Common Stock". The "Holders of
Company Common Stock" shall be defined as all holders of Company Common Stock
other than Acquiror, Merger Sub, any affiliates of Acquiror or Merger Sub or any
holders of Dissenting Shares.

     For purposes of this opinion we have, among other things:

          (i) reviewed certain publicly available financial statements and other
     business and financial information of the Company;

          (ii) reviewed certain internal financial statements and other
     financial and operating data concerning the Company prepared by the
     Company's management;

          (iii) reviewed certain financial forecasts and other forward looking
     financial information prepared by the Company's management;

          (iv) reviewed with Company's management the publicly available
     consensus estimates of research analysts on the Company's future financial
     performance;

          (v) held discussions with the management of the Company concerning the
     business, past and current operations, financing needs, financial condition
     and future prospects of the Company;

          (vi) reviewed the financial terms and conditions set forth in the
     Draft Agreement;

          (vii) reviewed the stock price and trading history of the Company;

          (viii) compared the financial performance of the Company and the
     prices and trading activity of Company Common Stock with that of certain
     other publicly traded companies comparable with the Company;
<PAGE>   2
Board of Directors
ADFlex Solutions, Inc.
July 1, 1999
Page  2

          (ix) compared the financial terms of the Offer and the Merger with the
     financial terms, to the extent publicly available, of other transactions
     that we deemed relevant;

          (x) prepared a discounted cash flow analysis of the Company;

          (xi) participated in discussions and negotiations among
     representatives of the Company and Acquiror and their financial and legal
     advisors, and

          (xii) made such other studies and inquiries, and took into account
     such other matter as we deemed relevant, including our assessment of
     general economic, market and monetary conditions.

     In our review and analysis, and in arriving at our opinion, we have assumed
and relied upon the accuracy and completeness of all of the financial and other
information provided to us (including information furnished to us orally or
otherwise discussed with us by Company management) or publicly available and
have neither attempted to verify, nor assumed responsibility for verifying, any
of such information. Except as set forth below, we have relied upon the
assurances of Company management that it is not aware of any facts that would
make such information inaccurate or misleading. Furthermore, we did not obtain
or make, or assume any responsibility for obtaining or making, any independent
evaluation or appraisal of the properties, assets or liabilities (contingent or
otherwise) of the Company, nor were we furnished with any such evaluation or
appraisal. With respect to the financial forecasts and projections (and the
assumptions and bases therefor) for the Company prepared by research analysts
that we have reviewed, upon the advice of the Company's management, we have
assumed that such forecasts and projections have been reasonably prepared in
good faith on the basis of reasonable assumptions and reflect the best currently
available estimates and judgments as to the future financial condition and
performance of the Company, and we have further assumed that such projections
and forecasts will be realized in the amounts and in the time periods currently
estimated. The Company's management has informed us that management's forecasts
and projections for the Company are currently out of date and that it would be
impractical to update the information. As a result, we have not relied on the
financial forecasts and projections of the Company's management for any of our
analyses. We have assumed that the Offer and the Merger will be consummated upon
the terms set forth in the Draft Agreement without material alteration thereof.
In addition, we have assumed that the historical financial statements of the
Company reviewed by us have been prepared and fairly presented in accordance
with U.S. generally accepted accounting principles consistently applied. We have
also assumed that the amount of the cash consideration to be paid in the Offer
and the Merger will not be reduced as a result of indemnification or other
provisions of the Draft Agreement. We have relied as to all legal matters
relevant to rendering our opinion on the advice of counsel.

     This opinion is necessarily based upon market, economic and other
conditions as in effect on, and information made available to us as of, the date
hereof. It should be understood that subsequent developments may affect the
conclusion expressed in this opinion and that we disclaim any undertaking or
obligation to advise any person of any change in any matter affecting this
opinion which may come or be brought to our attention after the date of this
opinion. Our opinion is limited to the fairness, from a financial point of view
and as to the date hereof, to the Holders of Company Common Stock of the cash
consideration to be paid in the Offer and the Merger. We do not express any
opinion as to (i) the value of any employee agreement or other arrangement
entered into in connection with the Offer and the Merger or (ii) any tax or
other consequences that might result from the Offer and the Merger. Our opinion
does not address the relative merits of the Offer and the Merger and the other
business strategies that the Company's Board of Directors has considered or may
be considering, nor does it address the decision of the Company's Board of
Directors to proceed with the Offer and the Merger.

     We are acting as financial advisor to the Company in connection with the
Offer and the Merger and will receive (i) a fee contingent upon the delivery of
this opinion and (ii) an additional fee contingent upon the
<PAGE>   3
Board of Directors
ADFlex Solutions, Inc.
July 1, 1999
Page  3

consummation of the Offer and the Merger. In addition, the Company has agreed to
indemnify us for certain liabilities that may arise out of our engagement. In
the past we acted as lead manager in the Company's initial public offering as
well as lead manager in the secondary offering. We maintain a market in the
shares of Company Common Stock. In the ordinary course of business, we may trade
in the Company's securities and Acquiror's securities for our own account and
the account of our customers and, accordingly, may at any time hold a long or
short position in the Company's securities or Acquiror's securities.

     BankBoston N.A., an affiliate of BancBoston Robertson Stephens Inc., is the
Company's primary lender. As of June 25, 1999, the Company's principal amount of
indebtedness to BankBoston N.A. was approximately $33.8 million (the "BankBoston
Indebtedness"). The Company is in covenant default with respect to the
BankBoston Indebtedness and has been in such covenant default since the first
quarter of 1999. Pursuant to the agreements entered into in connection with the
BankBoston Indebtedness (the "Loan Documents"), BankBoston N.A., on behalf of
the lender group, has the ability to immediately accelerate and demand payment
of the BankBoston Indebtedness. In May 1999, the Company requested that
BankBoston N.A., on behalf of the lender group, enter into a forbearance
agreement with respect to the BankBoston Indebtedness. In June, 1999, BankBoston
N.A. refused this request. Although BankBoston N.A. has not accelerated or
demanded payment of the BankBoston Indebtedness, BankBoston N.A. has reserved
its rights to take any actions and to seek any remedies available to it under
the Loan Documents. If the Offer and Merger are consummated as contemplated in
the Draft Agreement, we understand that Acquiror intends to repay the BankBoston
Indebtedness in its entirety and BankBoston N.A. may receive certain additional
fees related to the prepayment of the BankBoston Indebtedness. The Board of
Directors of the Company understands that BankBoston N.A. will benefit from the
consummation of the Offer and the Merger and the repayment of the BankBoston
Indebtedness.

     Our opinion expressed herein is provided for the information of the Board
of Directors of the Company in connection with its evaluation of the Offer and
the Merger. Our opinion is not intended to be and does not constitute a
recommendation to any stockholder of the Company whether or not to tender
his/her shares of Company Common Stock in the Offer or, if required, how to
vote, or whether or not to take any other action, with respect to Offer or the
Merger. This opinion may not be summarized, described or referred to or
furnished to any party except with our express prior written consent.

     Based upon and subject to the foregoing considerations, it is our opinion
that, as of the date hereof, the cash consideration to be paid in the Offer and
the Merger is fair to the Holders of Company Common Stock from a financial point
of view.

                                          Very truly yours,

                                          BANCBOSTON ROBERTSON STEPHENS INC.

                                          /s/ BANCBOSTON ROBERTSON STEPHENS INC.
