Hi Bill, I have been advised by Enthone in the past not to bake boards as it removes the organic coating...even at 80 deg. C for 2 hours is detrimental.... This was in relation to Entek 106A Marcelo > -----Original Message----- > From: [log in to unmask] [SMTP:[log in to unmask]] > Sent: Friday, December 05, 1997 2:36 PM > To: [log in to unmask] > Subject: Re: [TN] entek plus process > > Matthew: > > From my perspective, the question that needs to be addressed > FIRST is > where in the process is the ENTEK applied to the board. > > 1) ENTEK BEFORE or AFTER Bare Board Test > > By itself, ENTEK is an insulator. Therefore, if it is applied > PRIOR > to bare board testing, the bare board test probes can create > "false > opens" due to residue buildup on the tips of the probes. This > might indicate that ENTEK AFTER bare board test would be > better. > > On the other hand, a mild microetch is used to prepare the > surface > prior to ENTEK application. If the dip process is used and the > microetch is fresh (i.e. strong solution), excessive etching > can > result. This can result in circumferential barrel voids at > the > knee of the holes, where the copper is the thinnest. If ENTEK > is > applied AFTER TEST, this type of defect will not be discovered > until the board has been populated with expensive components. > > Some people subscribe to the policy "NO chemical operation > shall be > performed AFTER bare board testing". Each vendor's process > and > controls must be evaluated to assess the likelihood for this > type > of failure. > > 2) In-line vs. Batch > > In my opinion, in-line would be better and more repeatable, if > the > total volume of boards that the vendor processes warrant the > equipment expense. Properly managed, the dip process will > work. > > 3) "Spotted" Boards: > > Another "problem" to look out for is moisture spotting during > shipment. ENTEK uses a DI rinse in the process and, if vias > are > small (0.013" dia.), moisture can be trapped inside the barrel > of > those vias. Placing the "drip-dried" board in a plastic bag > for > shipment, can result in residual moisture STILL residing in > the > bag. Shipment of the boards to the final destination > (shipping > vibration, change in temperature, etc.) causes the moisture to > migrate to the inside surface of the bag and, in turn, back > onto > the board. The thickness of the ENTEK on the board will be > reduced > where there is intimate moisture contact. The appearance looks > like > "water spots" on a drinking glass. They COULD result in > localized > ENTEK "voids" and potentially cause solderability problems, if > the > boards are left on the shelf for an extended period of time. > > One test for "dryness" of a board is a deceptably simple one: > > a) Take a piece of colored construction paper (or the > cardboard > stiffener on the back of a pad of paper) that will darken > when > exposed to water and place it on a flat surface (e.g. > table). > > b) Take a "dry" board and firmly slap the face of the board > onto > the cardboard. If it shows dark spots on the cardboard when > the > fab is removed, the fab is NOT dry and could caule spotting > during shipment. > > My suggestion is to have the boards BAKED after ENTEK to > eliminate > this potential problem. > > I advocate the use of ENTEK for fine pitch QFP designs, because > of the > resultant pad flatness, as compared with HASL. However, it does > have > some "side effects" to watch out for. It is NOT the "panacea for > all > ills", but it is better than some of the alternatives in certain > designs. > > The above opinions are my own, etc.,etc., etc. > > Good Luck! > > Bill Fabry > Plantronics, Inc. > (408) 458-7555 > > e-mail: [log in to unmask] > > > ______________________________ Reply Separator > _________________________________ > Subject: [TN] entek plus process > Author: "TechNet Mail Forum." <[log in to unmask]> at INTERNET > Date: 12/5/97 9:58 AM > > > I am getting confusing responses from a board vendor that > uses in-line process, and from a board vendor that uses > dipping process to coat boards with Entek Plus. > > What are advantage/disavantage using either process? > > What are problem associated with boards that were > fabricated using dipping process? > > Does in-line processing provide better consistent and > controllable coating (typ: 0.35um) than dipping process? > > Is there any other coating thickness measurement technique > used by board vendors other than the sampling method > specified by Enthone using UV spectrophotometer? > > What are some of inspection method employed by board > vendors to check boards are coompletely dry prior packaging > and shipping? > > advance thanks > regards > Matthew > > ############################################################## > TechNet Mail List provided as a free service by IPC using LISTSERV > 1.8c > ############################################################## > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text > in the body: > To subscribe: SUBSCRIBE TECHNET <your full name> > To unsubscribe: SIGNOFF TECHNET > ############################################################## > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for > additional > information. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or > 847-509-9700 ext.311 > ############################################################## > > ############################################################## > TechNet Mail List provided as a free service by IPC using LISTSERV > 1.8c > ############################################################## > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE TECHNET <your full name> > To unsubscribe: SIGNOFF TECHNET > ############################################################## > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for > additional information. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or > 847-509-9700 ext.311 > ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. 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