Jowan Iven

Excellent point well taken!!!

You did something I always wanted to do, compare directly the 2 reflow
soldering techniques. I did not have the opportunity since I had either one
or the other.

Concerning the delamination, there could be other reasons why the boards
failed during reflow soldering in the reflow oven with no convection. But
your observations are valid.

Lee Whiteman
Senior Manufacturing Engineer
ACI / EMPF
Telephone: (610) 362-1200; Ext. 208
FAX: (610) 362-1290
E-Mail: [log in to unmask] <mailto:[log in to unmask]>


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Jowan Iven
> Sent: Friday, September 08, 2000 11:25 AM
> To: [log in to unmask]
> Subject: Re: [TN] Flex PCB's
>
>
> Hi Lee,
>
> I totally agree with the the first point you make.
> We bake flex boards at 130?C for 3 hours.
> Then the boards should be reflowed within 6 hours or else be stored in a
> conditioned environment (< 20% RH) when the batch is too large to handle
> within 6 hours.
>
> For the second remark you make ,I also prefer Full Convection reflowovens.
> Once we had an experiment ,where we compared two reflow ovens.
> The profiles ( not to be mistaken with the settings) were the
> same , but in
> one of the  ovens we didn't use convection .
> There was no delamination observed on the pcb that ran through  the full
> convection oven.
> But the pcb from the reflow oven with no convection , showed some
> delamination.
> So its my opinion that it is not quit possible to get the same
> results from
> a IR oven.
>
> Perhaps this wil shed some new light on the oven issue,
>
> Jowan  Iven
> Process  Engineer  Manufacturing
> Stork Electronics
>
>
> -----Original Message-----
> From:   Lee Whiteman [SMTP:[log in to unmask]]
> Sent:   Friday, September 08, 2000 2:37 PM
> To:     [log in to unmask]
> Subject:        Re: [TN] Flex PCB's
>
>  << File: ATT00001.htm >> Mick Thwaite,
>
> 1. PCB's should be baked out prior to use. Depending upon the PCB's
> material
> (FR4 vs.. polyimide), the board should be baked out at over 100C for
> between
> 1 - 4 hours. I've seen instances where people have baked out boards up to
> 24
> hours before use, but I believe 1 - 4 hours is sufficient.
>
> 2. Hot Air Convection vs.. IR Reflow. I would be more concerned with how
> well you control the reflow soldering process versus the type of reflow
> soldering process used. Hot Air Convection does provides better heat
> transfer than IR Reflow. However, I've done IR Reflow soldering with
> positive results on boards with SMT devices. I would recommend Hot Air
> Convection over IR Reflow, but if you currently have an IR Reflow
> oven, and
> you can't buy a new Hot Air Convection oven, with care you can
> get the same
> results with IR Reflow as with Hot Air Convection.
>
> 3. Too long ago, I used an anodized aluminum vacuum fixture to hold down
> parts for wire bonding, and it worked well. The deal was to design it
> taking
> into account the tolerances of the device.
>
> I hope these answers help you and that I did not strike out with these
> answers.
>
> Good Luck
>
> Lee Whiteman
> Senior Manufacturing Engineer
> ACI / EMPF
> Telephone: (610) 362-1200; Ext. 208
> FAX: (610) 362-1290
> E-Mail: [log in to unmask]
>
>     -----Original Message-----
>     From: TechNet [mailto:[log in to unmask]]On Behalf Of Mick Thwaite
>     Sent: Friday, September 08, 2000 4:02 AM
>     To: [log in to unmask]
>     Subject: [TN] Flex PCB's
>
>
>     We are just starting to use flex PCB's in our production area.
>
>     Is it true that the PCBs have to be dried prior to using as
> they absorb
> moisture quickly?
>
>     Is it also true that hot air is better than IR reflow?, and
>
>     Does anybody have any good ideas on the materials to use for
> the vacuum
> jig to hold down the panel during wire bonding?
>     We have used vacuum holds as small as 1.00 mm but still find that the
> PCB moves during bonding.....
>
>
>
>     Mick Thwaite
>
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