X3T9.2/92-94 Date: Fri, 13 Mar 92 08:54 GMT From: Dal Allan <0002501752@mcimail.com> To: X3T9.2 Subject: info pkg re 1988 Connector Decision CONNECTOR TIMES ARE HERE AGAIN...... In girding for the fray associated with the motion taken at the last meeting it seemed that committee members who did not endure the 'exciting' process of decisions in 1987-88 should be provided with background material. For those of us who were involved, the material should refresh our memories. One thing overlooked in the discussions at the last meeting was the 'change in sex' of the connectors between SCSI-1 and SCSI-2. For EMI and ESD reasons, the male half of a ribbon connector is mounted on the device and the female is on the cable. Texas Instruments made an impassioned plea that the most vulnerable compon- ent should be on the cable, and not on the device. In considering the move toward a ribbon connector, we should decide whether or not we want to return to the previous sex practices of ribbon connectors. NOTE: The following material is extracted from past issues of the ENDL Letter, and are not part of the committee record. Enjoy, USER CONSIDERATIONS Significant factors agreed on at November 1987 Connector Working Group: Benny Donaghue (Texas Instruments) had prepared a list of his concerns over what was necessary in choosing a microconnector. Bill Spence (Texas Instru- ments) had introduced Benny by letter, lauding his capabilities as a critic of connectors for over 20 years, who could differentiate between hyperbole and the facts. Benny had a number of points to make. o Select only one style. If that style is p&s, then the sockets must be on the bulkhead so that the more easily damaged pins are on the cable, the least expensive component. o Reliable service. Some form of idiot proofing is essential and an inter- nal barrier system must protect exposed contacts. This argument was used in favor of choosing ribbon style over p&s. o Be simple to assemble. Ensure that shield termination and strain relief using readily available cable can meet world wide agency requirements. Benny was concerned that the small footprint of the microconnector would cause retention problems due to the weight and bulk of the cable. o ESD. The shield integrity of the entire system from shield braid termina- tion through the back shell and across the shell interface must be comp- lete without any reliance upon the latching mechanism as an electrical circuit to ground. o Retention. A quick release retention scheme is more desirable than one which does not break away before damaging the interface components, the cable, the bulkhead or the equipment (pulling it onto the floor). This was an argument against jackscrews as he also mentioned the unfortunate propensity for the lock stud to come free thus making it impossible to remove the screw (because the stud is free wheeling on the inside of the cabinet). o Tooling. The connector chosen must be offered in a wide variety of conf- igurations and have tooling in place for cable assembly. Although not part of the standard, such tooling is essential. A "butcher shop" cable house has limited capability with microconnectors, so volume production must be easily achieved with tooling made available at a reasonable cost by the manufacturers. o Configurations. A wide variety must be available to satisfy all of the different system user and peripheral manufacturer's needs. o Sources. The selected connector must be available in quantity from at least three sources to ensure competition and reasonable prices. Benny cautioned the group about clumsiness and inattention, human traits which work to destroy any reasonable connector system. THE CONNECTOR SAGA - PAST HISTORY Questions out of October 1987 Plenary: +-------------------------------+-----------------------------------------+ | Is it gas tight? | What locking methods are used? | | How many mating cycles? | What wire sizes are supported? | | Can it be daisy chained? | What is the assembly procedure? | | Is it surface mountable? | What is the backpanel clearance? | | What are the tool costs? | What are the RFI characteristics? | | What is the availability? | What are the ESD characteristics? | | Are there multiple sources? | What are the bandwidth limitations? | | Are diecast parts available? | What are the dimensional tolerances? | | What is the retention force? | What are the vibration characteristics? | | Does it support round cable? | What are the impedance characteristics? | | Does it support ribbon cable? | What are the space/volume requirements? | +-------------------------------+-----------------------------------------+ Questions added at November 1987 Connector Working Group: +--------------------------+-------------------------------------------+ | Low profile | Minimum of 250 insertions | | Daisy chain | Viable latching mechanism | | 26 AWG wire | Acceptable insertion force | | Acceptable ESD | * Consistent conductor pin pairing | | * Male on cable ends | Discrete, PCB and IDC terminations | | Shielded/unshielded | * Bridge adapter to 100 mil connector | | 50 mil center spacings | Vertical and right angle configurations | +--------------------------+-------------------------------------------+ Manufacturers Lineup at November 1987 Connector Working Group: +----------+-----------------------+ | | Manufacture | | | T&R | Ribbon | | Prefer | Int | Ext | Int | Ext | +-------------------+----------+-----+-----+-----+-----+ | AMP | T&R | Yes | Yes | Yes | Yes | | Fujitsu | T&R | Yes | Yes | No | No | | Honda | T&R | Yes | Yes | Yes | Yes | +-------------------+----------+-----+-----+-----+-----+ | 3M | Ribbon-A | Yes | No | Yes | Yes | +-------------------+----------+-----+-----+-----+-----+ | Hirose | Ribbon-B | Yes | Yes | Yes | Yes | | Molex | Ribbon-B | No | No | Yes | Yes | | T&B | Ribbon-B | No | No | Yes | Yes | +-------------------+----------+-----+-----+-----+-----+ | Elco | Ribbon-C | No | No | Yes | Yes | +-------------------+----------+-----+-----+-----+-----+ | Burndy | Ribbon-D | Yes | Yes | Yes | Yes | +-------------------+----------+-----+-----+-----+-----+ Decision factors at the February 1988 Plenary: +-----+-----+-----+-----+-----+-----+ | |Hir- |Bur- | |Ste- | | | 3M | ose| ndy| AMP | wart| JAE | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Are there any patent issues? | N | N | N | N | N | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Are latches compatible within an | | | | | | | | intermating family? | Y | Y | Y | Y | Y | Y | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is piggyback available? | Y | Y | N | Y | Y | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is the latch "easy on/off" | N | Y | n/a | Y | Y | n/a | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is 50 position tooled? | Y | Y | Y | Y | N | Y | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is 68 position tooled? | Y | Y | Y | Y | N | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Do shielded & unshielded intermate? | Y | Y | Y | Y | Y | Y | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is surface mount tooled? | Y | Y | N | N | N | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Can it be run on surface mount line? | N | Y | Y | Y | N | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Are alternate sources tooled? | N | N | N | Y | N | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Are all configurations on-the-shelf? | | | | | | | | Shielded | Y | Y | N | Y | N | Y | | Unshielded | N | Y | N | Y | N | Y | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is 50 mil daisy chain tooled? | Y | Y | Y | Y | Y | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Is 25 mil daisy chain tooled? | Y | Y/N | N | Y | N | Y/N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | Are terminators tooled? | N | N | Y | Y | N | N | +--------------------------------------+-----+-----+-----+-----+-----+-----+ | What is the height above the board? | n/a |.287"| n/a |.287"|.230"|.276"| +--------------------------------------+-----+-----+-----+-----+-----+-----+ Voting sequence at the February 1988 Plenary: +----+----+----+----+----+----+ | 1 | 2 | 3 | 4 | 5 | 6 | +-----------------------------------+----+----+----+----+----+----+ | Amp, Fujitsu, Hirose, Honda | 35 | 34 | 33 | 30 | 29 | 32 | +-----------------------------------+----+----+----+----+----+----+ | Stewart, Viking | 27 | 22 | 23 | 26 | 26 | 27 | +-----------------------------------+----+----+----+----+----+----+ | 3M, Dupont-Berg, Elco, ITT-Cannon | 31 | 31 | 30 | 26 | 23 | | +-----------------------------------+----+----+----+----+----+----+ | Hirose, Molex, T&B | 26 | 23 | 21 | | | | +-----------------------------------+----+----+----+----+----+----+ | Burndy | 12 | 10 | | | | | +-----------------------------------+----+----+----+----+----+----+ | JAE | 1 | | | | | | +-----------------------------------+----+----+----+----+----+----+ | TelTec | 0 | | | | | | +-----------------------------------+----+----+----+----+----+----+