What is different about these capacitors that they cannot take the thermal
shock of wave soldering. I have experienced over the past few years the
cracking of 1206 and 0805 capacitors due to various stresses, and solved
various stress related issues with said capacitors (thanks to all the
consultants who have helped me with this issue, you know who you are!! :-}
). Since I have never used this specific size capacitor, i would like to
know if this is a problem so it can be added to a list of do's and don'ts
for design guidelines. Is the size the problem, or what?
Thanks
Ed Holton
Hella Electronics
[log in to unmask] on 07/02/98 02:19:14 PM
Please respond to [log in to unmask]; Please respond to [log in to unmask]
To: [log in to unmask]
cc: (bcc: Ed Holton/Hella North America Inc.)
Subject: Re: [TN] KEMET capacitor 2225 size --not suitable for wave solder
ing???
These caps cannot take the thermal shock associated with wave
contact, they will fracture and/or come off the board. If you are
finding them missing at ICT, they're in your solder pot chewing up your
pump and bearings. If this has been an ongoing issue, you should
probably drain/clean/refill your pot with new solder to prevent machine
damage and solder contamination from the ground up ceramic bits. If you
must put these on the bottom side of the board, look at:
- Wave carriers that will mask these locations, and process them as
reflowed parts, with paste rather than glue. You can selectively process
just the large ceramics or all bottom side SMT, and have the carrier
mask everything but the leaded components.
- Do bottom side reflow of all SMT and process top side leaded
components as pin-in-paste/intrusive reflow to eliminate wave
completely.
- As final consideration, hand solder them after wave if volumes are low
enough to accomodate. If hand soldering, use a quality galvanic skin
type soldering iron such as Me**al (careful avoidance of manufacturer
'plug'), to minimize the same thermal shock at hand solder.
Mike McMonagle
K*Tec Electronics
> -----Original Message-----
> From: Dhawan, Ashok [SMTP:[log in to unmask]]
> Sent: Thursday, July 02, 1998 12:57 PM
> To: [log in to unmask]
> Subject: [TN] KEMET capacitor 2225 size --not suitable for wave
> soldering???
>
> Is there anybody having experience on Wave Soldering Ceramic
> Capacitors
> C2225C225M5UAC ?
> We are using these caps on solderside of one of assembly (Gluing the
> Components ) .We are finding some of caps blowing off at ATE. Our
> manuf
> engr is suspecting wave thermal shock /mech shock?
>
> KEMET has in one of their application notes mentioned that this part
> should not be used for wave soldering. Special process profiles
> required. Any recommendation for our wave soldering Process Engineer?
>
> I will appreciate if somebody can share experience on Technet and
> provide info.
>
> thanks
>
>
>
> Ashok Dhawan P.ENG.
> Manufacturing Engineering
> Unisys Canada Inc.
> 51 Burmac Road
> Winnipeg R2J4C9
> CANADA
> Fone 204-257-9199
> Fax 204-257-9104
>
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