PLASTIC HOUSING DESIGNED TO ACCOMMODATE ELECTRONIC AND/OR MICROMECHANICAL COMPONENTS AND INTO WHICH CONDUCTOR TRACKS PASS

BOITIER EN MATIERE PLASTIQUE DESTINE A RECEVOIR DES COMPOSANTS ELECTRONIQUES ET/OU MICROMECANIQUES, ET DANS LEQUEL PASSENT DES TRACES CONDUCTEURS

English Abstract

The invention concerns a thermoplastic housing designed to hold electronic
and/or micromechanical components and into which metal conductor tracks pass,
the conductor tracks being injection moulded in one of the housing walls. The
thermoplastic has a flexural strength of at least 200 MPa.

French Abstract

La présente invention concerne un boîtier destiné à recevoir des composants électroniques et/ou micromécaniques. Il est fait d'une matière thermoplastique dans laquelle passent des tracés conducteurs métalliques qui, à cette fin, sont injectés dans une paroi du boîtier. La matière plastique présente une résistance à la flexion d'au moins 200 MPa.

Claims

- 5 -
Claims:
1. A housing which is made of a thermoplastic synthetic material and designed
to accommodate electronic and/or micromechanical components and into
which lead metallic leads which for this purpose embedded in a wall of the
housing by injection moulding,
characterised in that the thermoplastic synthetic material is selected to have aflexural strength of at least 200 MPa.
2. A housing according to claim 1 in which the synthetic material has a flexural strength of at least 250 MPa.
3. A housing as claimed in claim 1 or 2 in which the synthetic material is a PPS.
4. A housing as claimed in claim 3 in which the synthetic material is a glass fiber
filled PPS.
5. A housing as claimed in claim 3 or 4 in which the PPS-based synthetic material
exhibits a flexural strength of 265 MPa.

- 6 -
6. A housing as claimed in claim 4 in which the distribution of the glass fibers in
the synthetic material is isotropic or does exhibit merely a slight anisotropy.

Description

CA 02206097 1997-05-26
Bc97s041 J~WlBelPCTlEPg5~0~461 7t26.05. 1997
Pl ASnC HOUS~NG DESIGNED ~O J~:COi~,MODATE EL~C'rR~NIC AN~JOR
MlC:ROlJ11~C;H~,Nl~At. I:~OMpoNENT5 ANl~ INTO WHI~I COND~ICl OF~
TRACKS PASS.
5 The invention c~ el ns ~ ousin~ rnade of a U ,~r"~o~ lasti~ synthelic mat~orial d~-
signed to ~,n~nodate ele~roni~ andlor n~'cru~,ec~anic~l oo~ G~ ts and into
which l~ad m~taTlic leads which for this purpose ~re ~n-hecl~ed in a wall of th~h~usin~ by in;ec~ion mouldin~. In certain applications such housin~s ha\~e lo beh~rn~ic ~lly sealed. The l~ ior, where the le3d~ t~ave~se a wall of the h~usin~
1û c~nstlt~e~ a criti~l locali~- For the se~lin~ of the housing. Oflen such leads are
~ormed by punchin~ of metallic strips t~ a latticc whicl~ i8 pos~tion~ in ~n inie~
tion rnold for moul~in~ a p~rt of the housing so that the lattic~ be~".~s partly ~m-
bedded by i,; ~tion nlould;n~. l'h~ m~allic strip may consist o~ copper which is~ oated with alumini~. DifficulUes arise h~m the fact that rnetals and pla~ti~s dif~
15 fer, ~lo~rkably in their coefr;c ant of ~l~ermal exp~nsi~n. ~Ppper ~or ex~rnple h~as a
~en l of U)e""al e,~ ns;on of 17 x 10~1~Kwhereas the""op~d~lic synthetic
rnater~als typi~ally ~a~ ~ a ~o~r;e;en~ of ll l~r",d~ ~x~ansion be~veen 20 x 1 0~1~K
an~ 30 x 1 ~JrK. Under he~t loa~s which may oc~ur not oniy under certain appli-
c~tion conditions P~t already d~Jring the m~n~fa~t~re R~' th~ llousin~, particularly

-
rto ~ v~ al~e ~ MAK~ + AS~ 10
CA 02206097 1997-05-26
wltil~ adh~sives are being cured and whlie ~mpol~nts 3~e ~ n~;t~d by solder-
in~ tQ leads ~rhich a~e en,b~d~cl ~y ini~ction mouldin3""ed~anical stress6s ~r~
~n~.ale~ in the pEastic "~ . Due to the thsrnlal lo~d the p7~tic n,~t~rial will
slip along the nletallic l~ds. Partly this will result in a di~connection of the pla~tic
5 ~T~t~ l frorr th~ n~etel which i~ thc moo~ cec i~ not too b4d cin~ ~ho ~p
~hi~h is ~orn~ed b~ en the meS~llic surf~oe and 1he pla8tic matcrial i5 sul~i-
cientiy nar~ to gua. ~nlee a wffici~nt sealing ~ffeçt. It ~n~y, hov~vor, happe
that in th~ plastic ,nalerial fi~sures are formed ~ h e~ n~ cro~is~ or at riyht
~n~le~ to ~he ~etalli~ lea~s whereby ac~e~s~s to the g~p ~e~00n the lead and
10 ~h~ pl0~ m~l~l ial are form~d so that the housing will no lon~r b~ ti~ht.
It is well knawn in the 8rt to ke~p the differ~nce be~en the Ulerm~l ~xpan~ion
c~o~,-c ~.,. 1~ of met~ls ~nd pl~stic n,~le~ as l~w as pwsib!o by 8ele~tin~ appr~-
priats ~ate~ials and by sh~pin~ the lead~ so as to Ill;.".~li5~3 ~he ~Lf~3~s ~ r3G;~
th~ le~ds snd the s~Jrroundin3 pl2sti¢ fndlerial~ These measures proove, ho~1Evor~
15 rnerely partly ~ $sful; on the one hand the m~terials cannot ~e ~el~ctad ind~~en~ntly ~ince further uiteria h~ve to be met for e~ .,-pl~ wit~ r~ard ta electric
con~uctivity, surf~ nditi.~-" .,~cchan~ and li.~ 1ll8l stability of ~h~pe, resis-
tanOe ~;ns~ selvents, oil and ~resse, ~nd r~sis~ Palinst a3ein~; on the
other hand U161~ iC~ t~ maker;als, Y~hi~h are filled wlth glass ~bers to20 irnprove their m~h~nic~l and U,~r..,al stsbiiity, mostly show~n allis~lu~ y
Ule~ 11181 ~3A~13l ,~ion ooe~lcient ~vhid~ rn3kes it imposs,~la to sdapt their thermal ex-
pansion ~e~ficient ~ ;lly tc that of the lead~.

CA 02206097 1997-05-26
In ~lew of thes~ Facts it is an obje~t of the ~r~R~I~t in~rention to di~close a po~sibil-
ity how to i~ o~ the ti~yl ~ ss of8UCh h~usln~s.
Aco~rdi.)~ to the pres~nt inverttion this ~bje~ i~ acco.nplished by ~ houslng hav-
ing the features included ir ~im 1. ~n such ~ housing, which is n~3de o~ a ~her-
S mopld~tic synthetic ~--dt~rial ~nd d6si~l ~d to acc~m~)~odate ~ tr~l . C an~or
mlcl ur ,e~l ~a~ lpOI l~r ~t~ and into ~hidl l~ad metallic leads which for this
purpos~ sre ~mbed~e~ in a wall ~ the hou~ing b3~ cliot I mou~d~ng, th~ syn-
th~tic .,lat~r i~l is sel~ d tO h a~e a fl~xural ~r~ h of at le~st 2~0 MPa. Pre-
~errecl embodi~nts of th~ inYention ar~ tt~e ~ubjeot Of the ~epen~ent cl~in s.
10 S- ~prisin~ly it has bee~ found that the tel ~d~ to form fissures, which ext~nd
crosswi~ ~o ~he ieads, is ~e~Jc~, if th~ ~hermoplastic synth~tic n~ ri~l, into
which the le~ds are ~ Le~J~J by in,e ~ lion mouldingt is ~GI~_te~ to h~9Y~ a htgh
f~exural ~ n~ "~r~f~r~bly as ttigh a~ possibl~. A~ ty it is ~3ught to select
a ll IGI ",v,vla~l;c Sr~,th~lic ., Idt~l ial havin~ a flexural 3t~ t h of at least 20~ MPa,
~5 p,~.~Lly nlore lhan ~50 MPa. Parffcul3rly h~hiy ~ pffr~t~ro r~si~,rll thern~o-
p~asti~ n~ 15 like PPS exl~ibit ~IJch hi~h flexural stren~tl~s. Thus hard thermo-
pl~sti~ nnateri~ls on the ~asi~ ~f PPS ~re pr~ d. A PPS ~tlled with ~i~ss fibers
has proven particularl~ us~fu~; SU~t (n~t~rial is distribut~d by P~ILLIPS under the
b aJ~ a~ ~YTON R4XT. ~his matafial ~xhibi~ a flexural ~tf6n~ f 265 MP~ as
20 d~ ined accor~ y to ASTM D6~5S9 P~r~ ariy p~r~d ars ~lass fiber

CA 02206097 1997-05-26
d synthe~ic ~,.c,l~r;~'s ,,n whi~h t~ ~ 9s flbers are d~str~buted isotropically o~
ne~rly i~ 'ly ~n or~r to ~void an anisollv,,s~,~l ooe~i;c ~ nt of lll~r.llal ~xpa~
sion and at the ssrne time t~ get a high flex~ral ~tt ~ ,811,.
It i~ an ~dv. rlt~;6 of the invent;on th~t is even unne~sss~ry to a~l3pt the U ,~ ~, r;ll
5 a~pal~slon ~efr~ciE ~t ~f t~ rnlheti~ pl~stic ,~,~5le~ t~ ~hat ~ the met~llic leads
when s~le~ti.l~ a Uh~r,~ ti~ synthetic ~ t~ri~' with hi~h fle~wral st,e~,lyt~l, n~-
erlhe~ss ti~htly en~h~d~d leads are abt~inable.
~h~ enc,ossd single dr~u~ shOW5 ~ s~ti~llalV~eW of a part o~ a w~tl o~ ~ ho~s-
ing made of ~ ri~id pl~stic material in wni~ a lead in en ~e~d&~. The lead i~
p~rtiy covered witl~ a lay~r of S~K~ pla~ic " Iql~rial havin~ a thicknsss of merely
0.4 mm. Wh~n uslng a pla~Uc n~terial havin~ a flex~Jra~ s~r,gU~ of 19~ MPB
mi~o-fissu~0s have been foun~ In the n4 mm tl-i~l< p1astic l~yer a~ al~ro~
and~or "~ ~tldni~ 4n.~er~ents 1 ad been ~n~e~ed tc) th~ le~ds ~ ~lder-
ing and ~Fter th~ housi~ h~d ~eQn sealed, said mic~o~ sures resulting in 3 k:)8s~5 ~f ~ ss. If, 1~; ~1Jol~, a glass fib~r ~l~led PPS pl~stic m~t~r;~l haYir~ 8neXU
~o~ of 265 MPa w~s ~sed ~uch mic~o-fissures cou~d n~ r b~ discov~
er~d l~e tests have be~n carri~d out with h~u5ings hlle~ ~vith an oil and d~
si~ned to ~ ~ceivc a rni~ o~ ani~R~ a~lwltiul 1 senson
Not~: PPS rneans p~ o,~ e s~lphide

Representative Drawing